Human Rights Essay

Human Rights are those rights that are deemed to belong to all individuals by virtue of their humanity 1. Previously, these rights were referred to as â€Å"the rights of man† or natural rights. Because of this, human rights are ascribed to all humanity regardless of their citizenship or nationality. The human rights doctrine can, in this respect, come into direct conflict with other doctrines of the sovereignty of other governments in the world, and the law, because of the universality that has led to the pursuit of the agenda of human rights at stages of international co-operation in the era of post war2. The Human Rights Act has elicited a lot of divided opinion. Debate has risen in Britain as whether to repeal the Human Rights Act, (hereinafter referred to as the HRA), extend it or whether it should be replaced altogether with the British Human Rights (Hereinafter referred to BHR)3. Repealing the HRA refers to abolishing or evoking the act altogether while extending it will imply that, this Act could stay on longer without being repealed or cancelled by the British Government. In Britain, some fundamental individual freedoms are today protected by the Human Rights Act of 1998 which requires all the Britain law to obey the European Convention of 1950 on Human Rights (hereinafter ‘The ECHR’) and which also makes it possible for the convention to be enforceable in all the British Courts and makes it mandatory for the Judiciary to interpret the local law so that it complies with the convention4. The act came into existence over ten years and it seeks to protect the individual rights of people and has had a lasting impact in many fields of their private and public lives. The HR integrated the ECHR into the British law and therefore made it unlawful for any Public body or officer to act or behave in way which is incompatible with the convention5. The 1998 HRA made the ECHR to be part and parcel of the British National Law. Before that, the courts were only allowed to take the ECHR in very limited circumstances during domestic proceedings6. However, section 19 of the Act made it mandatory for any future legislation to contain compatibility with the ECHR. The Human Rights Act was in 1998 hailed to be a landmark statute but has elicited a lot of controversy and misconception. The HRA of 1998 has brought some certain elements into the legal system of Britain about the Human Rights of the European convention. In this Act, the British Courts are required to uphold and apply the ECHR in each and every decision that they make. This convention was developed to safeguard against the rejuvenation of Nazism and the protection of the rights it sought to protect after the Second World War7. The Articles which are contained in the Human Rights Convention proclaim among others the right to life which is contained in Article 2, prohibition of torture of human beings which is contained in Article 3, the prohibition of forced labor and slavery which is contained in Article 4, the right to security and liberty which is contained in Article 5, the right to a fair and just trial which is contained in article six, the prohibiting of extra legal punishment which is contained in article seven, the right to respect of the private family life of individuals which is contained in Article eight and the freedom of conscience, thought and religion which is contained in article nine. The convention also spells out the liberty of self expression that is found in Article 10 and the freedom of association and assembly that is clearly depicted in article eleven. The right to marriage and the prohibition of discrimination are contained in articles twelve and fourteen respectively 8. The legal modern approach of human rights that binds the governments to this Act arose from the United Nations Declaration on Human rights in 1948 which internationally developed a secular agreement on the rights of the human kind to provide the means through which the desire of the governments of the world could be able to prevent the recurrence of atrocities which were committed in WWII through setting of a common standard for all people and states 9. Should we repeal the HRA? The Human Rights Act should be repealed because it undermines the sovereignty of Britain as an independent state and therefore it should not be governed by laws from external sources. Given the fact that Britain is an independent country having its own laws and constitution to guide it in whatever undertakings that concerns it, there is no need for it to incorporate the ECHR since its laws have articles concerning the human rights. There is need to repeal the Human Rights Act because the Human Rights can well be covered under the British Bill of Rights 10.. The Human Rights Act should be repealed because it has undermined the authority of parliament and given the judges the ability to issue any declarations of incompatibility yet these judges have no empowerment to strike down any laws which are incompatible but instead, it is the government which must make a decision as to how to respond to any declaration. By repealing the HRA, the British government could have been empowered to make decisions affecting Britain to solely remain in Britain and by so doing, a culture of self independence will be created and this will enable the British citizens to enjoy their rights alongside the rights of the ordinary citizens in Britain 11. There are those who argue that the HRA should not be repealed but instead, it should be directly incorporated into the British law. This is because, given the fact that there is lack of a codified constitution which sets out the citizen’s rights, the British doctrine for the sovereignty of parliament cannot provide enough protection for the rights of individuals from a government which is intrusive. The HRA can therefore ensure that all these are achieved12. Repealing of the HRA would make the laws under it to be under the control of the Judges in Britain. By so doing, a complicated legal situation could be created and this could lead to threatening of the protection that is currently provided in the European Law on Human Rights. The Human Rights Act should therefore never be repealed or replaced with the British Bill of Rights but instead, it should be extended. This is because the British Courts are a backstop of preventing the infringement of the fundamental rights and as such, they command a great respect from the general public 13. Should we extend the HRA? The HRA should not be extended because it forces the government of Britain to obey the ECHR yet it has its own laws which it is supposed to protect to maintain its sovereignty. Forcing an independent country to obey foreign rules is like colonization and therefore it should not be extended because it infringes on the freedom of Britain as an independent country. The HRA should not be extended by the British Government because it does not deal with big issues of discrimination, torture or slavery and other things which are restricted largely to other countries and of which it is also responsible for the very down to earth principles of the right to privacy, food, housing, equality, health and freedom of speech. The HRA does not reaffirm these obligations in a real way that individuals can be able to forget and seek to set them in history and in stone14. The Human rights Act should be extended because it is a very important piece of legislation which has so far been issued by the British Government 15. The Act will make all the British People to be enlightened with the fact that all people are born with obligations which require them to treat other human beings with dignity and in a way which they also expect to be treated. This dignity is therefore not about philosophy or religion but a matter of consideration for other people and common dece ncy. For Britain to redress the balance, then it will not be easy for it alone, but for the society and a world which bases itself on the respect of human rights to intervene so that the continued struggle aimed at adjusting the current attitudes and explaining to other individuals why there is need to respect other people can be achieved. The Human Rights Act should therefore be extended so that these ideals are realized16. But contrary to this, the HRA should be extended because it does not go far enough and therefore gives numerous states chances in the Human Rights Convention for the governments to opt out of some certain provisions for the sake of their national security. On the contrary, the human Rights Act should not be extended because it could subject some poor citizens of Britain to punishment as a result of having to travel far in search of justice in a foreign court other than seeking justice within the local courts available in their resident country. The further extension of the Human Rights Act in Britain is therefore a blow to the common citizens of Britain 17. The HRA should not be replaced by the British Bill of Rights so that the British parliament cannot be able to abolish the HRA in the same way they do to the other laws. Currently, the HRA has got no privileged position in the British Law and therefore, it can easily be changed in the constitution without the need for special procedures 18. If it is incorporated into the British Bill of Rights (hereinafter â€Å"the BBR), it will become difficult for anyone to easily change it to suit his or her circumstances. The HRA should never be replaced with the British Bill of Rights as suggested by some of the conservatives like David Cameron but it should instead be extended so that that a culture of impunity cannot be created by the government. Calls by the democrats that the Human Rights Act should never be repealed should therefore be never be supported. Instead, the Human Rights Act should be replaced by the British Bill of Rights so that the people of Britain can be able to reaffirm their independence by having their own domestic laws to govern them other than relying on international laws. 19. On the other hand, swapping the HRA with the BBR can be a sure way of restoring the responsibility for the balancing act to politicians in Britain which the general public can easily elect or boot out according to their preferences. Indeed, the establishment of the BBR will make the British government to have absolute power as a result of the rediscovered freedom which will positively develop democracy in and justice in the country. Should we replace the HRA with the BBR? The Human Rights Act should be replaced with a Bill of Rights because this Act is a means through which some parts of Human Rights contained in the European Convention are brought into the British Law books. The HRA clearly sets out the responsibilities of the people of Britain as a society since with any form of legislation; different people would often try to seek interpretation of its content to satisfy their own selfish ends. In essence, such people will popularly start shouting about the trampling and violation of human rights in any case the other channels are exhausted but funnily enough, this is possible because of the real principle which is enacted in the Human Rights Act itself20. Some people argue that the HRA should not be replaced with the British Bill of Rights so that rogue politicians are tamed by laws which are universally established and recognized. Given the fact that the decisions will remain in the country and not subject to laws from outside, it will create more room for bribery to exist and develop roots since people who make major decisions about human rights are located in one specific county. Attempts to replace the HRA with the British Bill of Rights should be discarded because it could be detrimental to the British people. People are entitled towards voicing their opinions if they feel there is violation of their human rights. The Act therefore, remains the best for delivering justice to all people without any fear or favor 21. The HRA should be extended because it gives the British people the legal rights to stand up and be counted and should not be discounted like any other politically correct set of legislation. For the British people to better understand the Human Rights Act at its infancy, then they have to be aware that they have rights to know what their law makers do on their behalf and not solely rely on the media for the interpretation of the law decisions since they can easily be outraged by headlines which are too sensational. Since all the British people are members of their respective societies, then they have to bring with them responsibilities along with the rights because it is their responsibility to know that as much as they may be incensed with the headlines, they are the same laws which protect them as individuals and as a community 22 The British government should therefore not diminish the Human Rights Act but instead better understand and appreciate it. There should be no retreat over the Human Rights Act and its critics should be brought on board to understand the benefits it brings the country. The Human Rights Act should be extended because the creation of the British Bill of Rights will not make it possible for the incorporation and builds on the British obligations which are incorporated in the ECHR. This is because once the laws are enshrined in the British Law, then all the Human Rights Act could have totally been overhauled and replaced by the British Bill of Rights. Rather than the British government seeks to diminish or repeal the Human Rights Act, it should instead extend it and commit itself fully to the ECHR23. The British government should also be aware that by seeking to swap the HRA with the BBR, then they could have opened up room for the creation of significant legal problems which would arise as a result of reduction of any of the protections which are guaranteed and contained under the ECHR. The HRA should not be repealed because in any case it was to be repealed, and then it will not make any major difference because even if the parliament repeals it, the Courts can, by themselves, decide to enforce it anyway. According to the President of the Supreme Court in Britain, no great impact could be achieved if parliament chose to repeal the Human Rights Act because to him, the Act has already achieved the â€Å"Constitutional Statutes† which render them very impossible to repeal24. The Human Rights Act 1998 should be upheld and even be extended because it has changed the constitutional role of the British Courts as far as domestic legislation is concerned since all legislation in Britain must now be fully interpreted in accordance with the rights contained in the European convention. The implementation of the Human Rights Act has therefore changed the way the constitution has evolved and also changed the roles of the judiciary. This is because the judiciary has adapted so as to incorporate the HRA25. The Human Rights Act should be repealed or replaced by the British Bill of Rights since it is clear that in circumstances where it is difficult to interpret legislation in line with the European Community on Human Rights convention, then the British law will be given prevalence over the contravention. The Human Rights Act should be re-branded into the British Bill of Rights because it can n improve the public’s perception26. This is true because it is Act’s text that critics of the Human Rights are against and they are against the public bodies the decisions by the courts that people do not like. We should therefore, repeal or even substitute the HRA with the BBR before it even survives the stage of adolescence because the politicians who are very well known for permitting internment on a yearly basis cannot be trusted to build on the existing freedoms and rights but instead, they will aim at destroying the same27. The Human Rights Acts of 1998 which incorporated the ECHR into British law should not be repealed or even be replaced by the BBR because it gives the citizens statutory rights to enable them enforce their Human Rights in any Court in Britain 28. These rights were brought home by the integration of the ECHR, and therefore, made it easier for British Citizens to access them locally in their national courts. The incorporation of these conventions into the British laws therefore, not only provided a ceiling but also a floor for human rights. The Human Rights Act should be extended because it gives parliament the freedom to enhance the rights for instance by a Freedom of information Act which is contained in article 40. The British citizens were very privileged after the full implementation of the Human Rights Act in the year 2000 because they were able to claim their rights under legislation in a British Court rather than in Strasbourg where the final arbiter on interpretation of the convention of the ECHR is located. It should therefore, be noted that the sole reason of introducing the HRA in Britain was actually to bring the rights home to the people of Britain29. The Human Rights Act should not be extended because it does not in any way create new human rights or take away any existing human rights. Instead, the HRA followed the devastation that was caused by the World War II and aimed at protecting the basic freedoms and rights of the British people. The HRA seeks to enable the British Citizens to enforce their human rights locally in the courts in the UK without necessarily taking their cases to Strasbourg through provision of easier and better access to rights which currently exist. On the hand, extending the Human Rights Act is beneficial for the British people because those people who are against it have been known to have moral laxity and ignorance of the law. This is because the Human Rights Act empowers people to promote their interests. The human Rights Act should be upheld and extended because it belongs to all the human kind on account of their humanities and not based on the membership of the narrower classifications like ethnicity, class or citizenship. Unlike the British Bill of Rights which may tend to exclude by definition the non-citizens of a country from its protection, the Human Rights Act seeks to protect every human being regardless of where one comes from, the skin color, age or gender. Individuals like the undocumented employees, a single mum who loses all her benefits and the inmates in Guantanamo Bay actually lack the state or law which can protect them. For such people to enjoy the benefits of humanity and the rights associated with it, passing of a new British Bill of rights or keeping the initial Human Rights Act adds nothing to their lives30. The HRA should not be extended because it does not enlarge the remedies or rights of people in the United Kingdom whose rights in the convention have been violated but instead it enables those remedies and rights to be enforced and asserted by the domestic courts in Britain and not by recourse in Strasbourg. The Act should be extended because since its implementation, it has had a great deal of positive influence on the British Courts and therefore led to substantial improvement on the quality of public administration by the Executive, the public bodies, the Judges and the parliament in general. The replacement of the Human Rights Act by the British Bill of Rights will compromise the quality of these public administration institutions31. The Human Rights Act should not be repealed because it could lead to the prevention of the United Kingdom citizens from exercising their fundamental rights in the UK Courts and therefore leading to prolonged delays for the citizens who would be forced to present their appeals to the European Community on Human Rights in Strasbourg in order to assert their rights. The HRA should be replaced by the BBR as suggested by the British government which pointed out that they may build on the HRA to build a British Bill of Duties and rights. However such an attempt by the government is prone to bring success because of questions that have been raised in relation with these proposals. Among the questions that have been raised are whether there exist things like the rights for the British people or the British rights and how such rights can effectively operate within the framework of devolution to Wales, Northern Ireland and Scotland. Questions have also been raised as to whether there should be any inclusion of the economic and social rights within the British Bill of rights. The Human Rights Act should therefore be left the way it is and never be replaced by the British Bill of Rights because it could lead to so many legal complications in Britain32. The Human Rights Act should not be replaced into British Human Rights because the Bill of Rights could bring in ideas of making some of the additional rights in the Bill of Rights to be justifiable and therefore making the judiciary to further expand its scope of influence on issues which could be better handled by the parliamentarians. The HRA should not be replaced by the British Bill of Rights because there is a lot of confusion which has continued to reign as to whether the New Bill of Rights would comfortably sit alongside the Human Rights Act or it would be a direct replacement of the Human Rights Act. Instead of having two documents which would be unhelpful to the people it will be preferable to have a single document (the Human Rights Act) which adds to the ECHR33. The Human Rights Act should be repealed or even be replaced by the British Bill of Rights depending on the public good because it was enacted by parliament in 1998 and should therefore be fully discussed to determine whether the advantages outweigh the disadvantages. The British government should therefore place its focus on the human rights as a way of justifying and improving the official decision making rather than automatically making it to become a legal issue. In cases where the public authorities feel the need to tamper with the individual human rights, then must have genuine motives and follow fair and just procedures. In addition, the Act should not be repealed or be replaced by the British Bill of Rights because it is good for the British people. What needs to be done is to improve education about the Human Rights Act among the public to ensure that it occupies a more strategic position in schools and colleges. This is the right time to sell the true values of the Human Rights Act to the general public, something that has never been done after the Act became effective. By so doing, the public would be in a better position to be informed as to whether to repeal the Human Rights Act, repeal it or extend it34. People who support the HRA rgue that it should be extended because it is the safe and sure channel of giving protection to the marginalized and most vulnerable members of any society. They claim that anyone who is in Britain for any reason is entitled towards fundamental human rights which the public and the government are duly and legally obliged to obey and respect. This is because the Human Rights Act of 1998 made them to become law. Similarly, the Act should be extended because the rights contained in the convention not only deals with matters of death and life but also affects the rights possesses by people in their everyday life reflected in what they do, say and their beliefs.

Economics Commentary †article on the Haitian Earthquake Essay

IN JANUARY last year, the quake causes the 2004 Asian tsunami, which kill 250,000 people and 300,000 injured. People were living under sheeting strung across wooden poles. There were too many vulnerable homeless people that aid agency can’t fit them in tens. People are trapped in supermarkets, debris and so on. I feel really sorry for them and I hope casualty’s family can be rest in peace. First of all, there will be a change in Haiti’s economy because there’s a huge effect of Haiti’s production. Haiti lost 250,000 people and 300,000 people were injured. They lost loads of labor and enterprise just because of this. Labor are human resources providing power to make goods and services Enterprise is a firm is an owner of a factory or company e.g. Nike, Apple. Capitals such as Houses, hospitals and factories were destroyed. Capital is man made resources that use for production. Many animals got kill by this earthquake and tsunami and destroyed timbers there’s loss of land. Land is natural resources that can’t add by human. Clearly, Haiti’s production is decreasing. In this case, we can use a PPF to explain the situation. PPF is a curve that shows the combinations of 2 or more goods that can be produced using all available resources. Here’s the PPF of Haiti before tsunami. PFF1 is Haiti’s PPF before tsunami and PPF2 is Haiti’s PPF after tsunami The PPF shift to the left means there’s decrease at both actual and potential output. Actual output is what the country is currently producing and potential output is the maximum outputs you can produce will all currently resource. Because Haiti lost a lot of capitals, land, labor and enterprise, its production is running down. Therefore, it’s PPF shifts inward. There’s also economic decline and economic deterioration. Economic decline is the percent decrease in real GDP per annum and economic deterioration is decrease in living standard for everyone in the country. There is a shift of PPF because of the environment factors (earthquake and tsunami). There was a change of Haiti people’s demand because of the tsunami and earthquake. Demand is amount of a good or service that consumer are will and able to buy at a given price over a period a time. What’s the change of Haiti people’s demand? Tsunami and earthquake destroyed a lot things, one of them is food. Haiti people are in starvation, there’s no more flesh food for them so their demand of canned food rose. It is because inferior good’s demand if rise when there’s war, natural disaster. Inferior good is a good that can replace another good as a substitute. The demand of Haiti people’s canned food This is a demand curve shows people in Haiti’s demand of canned food rise from D1 to D2. Because the demand determinate is not price of the good of itself, it’s environment, there’s a shift of demand curve to the right. Demand determinants are factors that can affect the demand such as: price, consumer income, and low populations†¦ Evolution Haiti’s earthquake and tsunami are lost and a pain we would never wanted to happen and they took millions of people’s life away and destroyed thousands homes. Here are few solutions I think it might help to raise back the economy of Haiti. First of all is asking UN for help. The United Nations (UN) is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace. United nation will usually provided aid and food for refugees. Second is building hospitals and factories. Recovering labor and capital is an important step to get the economy back on track. Education is more important in Haiti than other countries. They need new blood to contribute for the society and that’s where education is needed. ‘Good people equal good country’.

Physics Notes

Gravitation Gravitational field strength at a point is defined as the gravitational force per unit mass at that point. Newton's law of gravitation: The (mutual) gravitational force F between two point masses M and m separated by a distance r is given by F =| GMm| (where G: Universal gravitational constant)| | r2| | or, the gravitational force of between two point masses is proportional to the product of their masses ; inversely proportional to the square of their separation. Gravitational field strength at a point is the gravitational force per unit mass at that point. It is a vector and its S. I. unit is N kg-1.By definition, g = F / m By Newton Law of Gravitation, F = GMm / r2 Combining, magnitude of g = GM / r2 Therefore g = GM / r2, M = Mass of object â€Å"creating† the field Example 1: Assuming that the Earth is a uniform sphere of radius 6. 4 x 106 m and mass 6. 0 x 1024 kg, find the gravitational field strength g at a point: (a) on the surface, g = GM / r2 = (6. 67 ? 1 0-11)(6. 0 x 1024) / (6. 4 x 106)2 = 9. 77ms-2 (b) at height 0. 50 times the radius of above the Earth's surface. g = GM / r2 = (6. 67 ? 10-11)(6. 0 x 1024) / ( (1. 5 ? 6. 4 x 106)2 = 4. 34ms-2 Example 2: The acceleration due to gravity at the Earth's surface is 9. 0ms-2. Calculate the acceleration due to gravity on a planet which has the same density but twice the radius of Earth. g = GM / r2 gP / gE = MPrE2 / MErP2 = (4/3) ? rP3rE2? P / (4/3) ? rE3rP2? E = rP / rE = 2 Hence gP = 2 x 9. 81 = 19. 6ms-2 Assuming that Earth is a uniform sphere of mass M. The magnitude of the gravitational force from Earth on a particle of mass m, located outside Earth a distance r from the centre of the Earth is F = GMm / r2. When a particle is released, it will fall towards the centre of the Earth, as a result of the gravitational force with an acceleration ag. FG = mag ag = GM / r2Hence ag = g Thus gravitational field strength g is also numerically equal to the acceleration of free fall. Example 1: A ship is at rest on the Earth's equator. Assuming the earth to be a perfect sphere of radius R and the acceleration due to gravity at the poles is go, express its apparent weight, N, of a body of mass m in terms of m, go, R and T (the period of the earth's rotation about its axis, which is one day). At the North Pole, the gravitational attraction is F = GMEm / R2 = mgo At the equator, Normal Reaction Force on ship by Earth = Gravitational attraction – centripetal force N = mgo – mR? = mgo – mR (2? / T)2 Gravitational potential at a point is defined as the work done (by an external agent) in bringing a unit mass from infinity to that point (without changing its kinetic energy). ? = W / m = -GM / r Why gravitational potential values are always negative? As the gravitational force on the mass is attractive, the work done by an ext agent in bringing unit mass from infinity to any point in the field will be negative work {as the force exerted by the ext agent is opp osite in direction to the displacement to ensure that ? KE = 0} Hence by the definition of negative work, all values of ? re negative. g = -| d? | = – gradient of ? -r graph {Analogy: E = -dV/dx}| | dr| | Gravitational potential energy U of a mass m at a point in the gravitational field of another mass M, is the work done in bringing that mass m {NOT: unit mass, or a mass} from infinity to that point. ; U = m ? = -GMm / r Change in GPE, ? U = mgh only if g is constant over the distance h; {; h;; radius of planet} otherwise, must use: ? U = m? f-m? i | Aspects| Electric Field| Gravitational Field| 1. | Quantity interacting with or producing the field| Charge Q| Mass M| 2. Definition of Field Strength| Force per unit positive charge E = F / q| Force per unit mass g = F / M| 3. | Force between two Point Charges or Masses| Coulomb's Law: Fe = Q1Q2 / 4 or2| Newton's Law of Gravitation: Fg = G (GMm / r2)| 4. | Field Strength of isolated Point Charge or Mass| E = Q / 4 or2| g = G (G M / r2)| 5. | Definition of Potential| Work done in bringing a unit positive charge from infinity to the point; V = W /Q| Work done in bringing a unit mass from infinity to the point; ? = W / M| 6. | Potential of isolated Point Charge or Mass| V = Q / 4 or| ? -G (M / r)| 7. | Change in Potential Energy| ? U = q ? V| ? U = m | Total Energy of a Satellite = GPE + KE = (-GMm / r) + ? (GMm / r) Escape Speed of a Satellite By Conservation of Energy, Initial KE| +| Initial GPE| =| Final KE| +| Final GPE| (? mvE2)| +| (-GMm / r)| =| (0)| +| (0)| Thus escape speed, vE = v(2GM / R) Note : Escape speed of an object is independent of its mass For a satellite in circular orbit, â€Å"the centripetal force is provided by the gravitational force† {Must always state what force is providing the centripetal force before following eqn is used! Hence GMm / r2 = mv2 / r = mr? 2 = mr (2? / T)2 A satellite does not move in the direction of the gravitational force {ie it stays in its circular orbi t} because: the gravitational force exerted by the Earth on the satellite is just sufficient to cause the centripetal acceleration but not enough to also pull it down towards the Earth. {This explains also why the Moon does not fall towards the Earth} Geostationary satellite is one which is always above a certain point on the Earth (as the Earth rotates about its axis. For a geostationary orbit: T = 24 hrs, orbital radius (; height) are fixed values from the centre of the Earth, ang velocity w is also a fixed value; rotates fr west to east. However, the mass of the satellite is NOT a particular value ; hence the ke, gpe, ; the centripetal force are also not fixed values {ie their values depend on the mass of the geostationary satellite. } A geostationary orbit must lie in the equatorial plane of the earth because it must accelerate in a plane where the centre of Earth lies since the net orce exerted on the satellite is the Earth's gravitational force, which is directed towards the c entre of Earth. {Alternatively, may explain by showing why it's impossible for a satellite in a non-equatorial plane to be geostationary. } Thermal Physics Internal Energy: is the sum of the kinetic energy of the molecules due to its random motion ; the potential energy of the molecules due to the intermolecular forces. Internal energy is determined by the values of the current state and is independent of how the state is arrived at. You can read also Thin Film Solar CellThus if a system undergoes a series of changes from one state A to another state B, its change in internal energy is the same, regardless of which path {the changes in the p ; V} it has taken to get from A to B. Since Kinetic Energy proportional to temp, and internal energy of the system = sum of its Kinetic Energy and Potential Energy, a rise in temperature will cause a rise in Kinetic Energy and thus an increase in internal energy. If two bodies are in thermal equilibrium, there is no net flow of heat energy between them and they have the same temperature. NB: this does not imply they must have the same internal energy as internal energy depends also on the number of molecules in the 2 bodies, which is unknown here} Thermodynamic (Kelvin) scale of temperature: theoretical scale that is independent of the properties of any particular substance. An absolute scale of temp is a temp scale which does not depend on the property of any particular subs tance (ie the thermodynamic scale) Absolute zero: Temperature at which all substances have a minimum internal energy {NOT: zero internal energy. } T/K = T/ °C + 273. 15, by definition of the Celsius scale.Specific heat capacity is defined as the amount of heat energy needed to produce unit temperature change {NOT: by 1 K} for unit mass {NOT: 1 kg} of a substance, without causing a change in state. c = Q / m? T Specific latent heat of vaporisation is defined as the amount of heat energy needed to change unit mass of a substance from liquid phase to gaseous phase without a change of temperature. Specific latent heat of fusion is defined as the amount of heat energy needed to change unit mass of a substance from solid phase to liquid phase without a change of temperature L = Q / m {for both cases of vaporisation ; melting}The specific latent heat of vaporisation is greater than the specific latent heat of fusion for a given substance because * During vaporisation, there is a greater increase in volume than in fusion, * Thus more work is done against atmospheric pressure during vaporisation, * The increase in vol also means the INCREASE IN THE (MOLECULAR) POTENTIAL ENERGY, ; hence, internal energy, during vaporisation more than that during melting, * Hence by 1st Law of Thermodynamics, heat supplied during vaporisation more than that during melting; hence lv ; lf {since Q = ml = ?U – W}. Note: 1. the use of comparative terms: greater, more, and; 2. the increase in internal energy is due to an increase in the PE, NOT KE of molecules 3. the system here is NOT to be considered as an ideal gas system Similarly, you need to explain why, when a liq is boiling, thermal energy is being supplied, and yet, the temp of the liq does not change. | Melting| Boiling| Evaporation| Occurrence| Throughout the substance, at fixed temperature and pressure| On the surface, at all temperatures|Spacing(vol) ; PE of molecules| Increase slightly| Increase significantly| | Tempera ture ; hence KE of molecules| Remains constant during process| Decrease for remaining liquid| First Law of Thermodynamics: The increase in internal energy of a system is equal to the sum of the heat supplied to the system and the work done on the system. ?U = W + Q| ? U: Increase in internal energy of the system Q: Heat supplied to the system W: work done on the system| {Need to recall the sign convention for all 3 terms} Work is done by a gas when it expands; work is done on a gas when it is ompressed. W = area under pressure – volume graph. For constant pressure {isobaric process}, Work done = pressure x ? Volume Isothermal process: a process where T = const {? U = 0 for ideal gas} ? U for a cycle = 0 {since U ? T, ; ? T = 0 for a cycle } Equation of state for an ideal gas: p V = n R T, where T is in Kelvin {NOT:  °C}, n: no. of moles. p V = N k T, where N: no. of molecules, k:Boltzmann const Ideal Gas: a gas which obeys the ideal gas equation pV = nRT FOR ALL VALUES OF P , V ; T Avogadro constant: defined as the number of atoms in 12g of carbon-12.It is thus the number of particles (atoms or molecules) in one mole of substance. For an ideal gas, internal energy U = Sum of the KE of the molecules only {since PE = 0 for ideal gas} U = N x? m ;c2; = N x (3/2)kT {for monatomic gas} * U depends on T and number of molecules N * U ? T for a given number of molecules Ave KE of a molecule, ? m ;c2; ? T {T in K: not  °C} Dynamics Newton's laws of motion: Newton's First Law Every body continues in a state of rest or uniform motion in a straight line unless a net (external) force acts on it. Newton's Second LawThe rate of change of momentum of a body is directly proportional to the net force acting on the body, and the momentum change takes place in the direction of the net force. Newton's Third Law When object X exerts a force on object Y, object Y exerts a force of the same type that is equal in magnitude and opposite in direction on object X. The two force s ALWAYS act on different objects and they form an action-reaction pair. Linear momentum and its conservation: Mass: is a measure of the amount of matter in a body, ; is the property of a body which resists change in motion.Weight: is the force of gravitational attraction (exerted by the Earth) on a body. Linear momentum: of a body is defined as the product of its mass and velocity ie p = m v Impulse of a force (I): is defined as the product of the force and the time ? t during which it acts ie I = F x ? t {for force which is const over the duration ? t} For a variable force, the impulse I = Area under the F-t graph { ? Fdt; may need to â€Å"count squares†} Impulse is equal in magnitude to the change in momentum of the body acted on by the force.Hence the change in momentum of the body is equal in mag to the area under a (net) force-time graph. {Incorrect to define impulse as change in momentum} Force: is defined as the rate of change of momentum, ie F = [ m (v – u) ] / t = ma or F = v dm / dt The {one} Newton: is defined as the force needed to accelerate a mass of 1 kg by 1 m s-2. Principle of Conservation of Linear Momentum: When objects of a system interact, their total momentum before and after interaction are equal if no net (external) force acts on the system. * The total momentum of an isolated system is constant m1 u1 + m2 u2 = m1 v1 + m2 v2 if net F = 0 {for all collisions } NB: Total momentum DURING the interaction/collision is also conserved. (Perfectly) elastic collision: Both momentum ; kinetic energy of the system are conserved. Inelastic collision: Only momentum is conserved, total kinetic energy is not conserved. Perfectly inelastic collision: Only momentum is conserved, and the particles stick together after collision. (i. e. move with the same velocity. ) For all elastic collisions, u1 – u2 = v2 – v1 ie. relative speed of approach = relative speed of separation or, ? m1u12 + ? m2u22 = ? m1v12 + ? 2v22 In inelastic collisions, total energy is conserved but Kinetic Energy may be converted into other forms of energy such as sound and heat energy. Current of Electricity Electric current is the rate of flow of charge. {NOT: charged particles} Electric charge Q passing a point is defined as the product of the (steady) current at that point and the time for which the current flows, Q = I t One coulomb is defined as the charge flowing per second pass a point at which the current is one ampere. Example 1: An ion beam of singly-charged Na+ and K+ ions is passing through vacuum. If the beam current is 20 ?A, calculate the total number of ions passing any fixed point in the beam per second. (The charge on each ion is 1. 6 x 10-19 C. ) Current, I = Q / t = Ne / t where N is the no. of ions and e is the charge on one ion. No. of ions per second = N / t = I / e = (20 x 10-6) / (1. 6 x 10-19) = 1. 25 x 10-14 Potential difference is defined as the energy transferred from electrical energy to other forms of e nergy when unit charge passes through an electrical device, V = W / Q P. D. = Energy Transferred / Charge = Power / Current or, is the ratio of the power supplied to the device to the current flowing, V = P / IThe volt: is defined as the potential difference between 2 pts in a circuit in which one joule of energy is converted from electrical to non-electrical energy when one coulomb passes from 1 pt to the other, ie 1 volt = One joule per coulomb Difference between Potential and Potential Difference (PD): The potential at a point of the circuit is due to the amount of charge present along with the energy of the charges. Thus, the potential along circuit drops from the positive terminal to negative terminal, and potential differs from points to points. Potential Difference refers to the difference in potential between any given two points.For example, if the potential of point A is 1 V and the potential at point B is 5 V, the PD across AB, or VAB , is 4 V. In addition, when there is no energy loss between two points of the circuit, the potential of these points is same and thus the PD across is 0 V. Example 2: A current of 5 mA passes through a bulb for 1 minute. The potential difference across the bulb is 4 V. Calculate: (a) The amount of charge passing through the bulb in 1 minute. Charge Q = I t = 5 x 10-3 x 60 = 0. 3 C (b) The work done to operate the bulb for 1 minute. Potential difference across the bulb = W / Q 4 = W / 0. Work done to operate the bulb for 1 minute = 0. 3 x 4 = 1. 2 J Electrical Power, P = V I = I2 / R = V2 / R {Brightness of a lamp is determined by the power dissipated, NOT: by V, or I or R alone} Example 3: A high-voltage transmission line with a resistance of 0. 4 ? km-1 carries a current of 500 A. The line is at a potential of 1200 kV at the power station and carries the current to a city located 160 km from the power station. Calculate (a) the power loss in the line. The power loss in the line P = I2 R = 5002 x 0. 4 x 160 = 16 MW (b) the fraction of the transmitted power that is lost.The total power transmitted = I V = 500 x 1200 x 103 = 600 MW The fraction of power loss = 16 / 600 = 0. 267 Resistance is defined as the ratio of the potential difference across a component to the current flowing through it , R = VI {It is NOT defined as the gradient of a V-I graph; however for an ohmic conductor, its resistance equals the gradient of its V-I graph as this graph is a straight line which passes through the origin} The Ohm: is the resistance of a resistor if there is a current of 1 A flowing through it when the pd across it is 1 V, ie, 1 ? = One volt per ampere Example 4:In the circuit below, the voltmeter reading is 8. 00 V and the ammeter reading is 2. 00 A. Calculate the resistance of R. Resistance of R = V / I = 8 / 2 = 4. 0 ? | | Temperature characteristics of thermistors: The resistance (i. e. the ratio V / I) is constant because metallic conductors at constant temperature obey Ohm's Law. | As V increases, the temperature increases, resulting in an increase in the amplitude of vibration of ions and the collision frequency of electrons with the lattice ions. Hence the resistance of the filament increases with V. | A thermistor is made from semi-conductors.As V increases, temperature increases. This releases more charge carriers (electrons and holes) from the lattice, thus reducing the resistance of the thermistor. Hence, resistance decreases as temperature increases. | In forward bias, a diode has low resistance. In reverse bias, the diode has high resistance until the breakdown voltage is reached. | Ohm's law: The current in a component is proportional to the potential difference across it provided physical conditions (eg temp) stay constant. R = ? L / A {for a conductor of length l, uniform x-sect area A and resistivity ? Resistivity is defined as the resistance of a material of unit cross-sectional area and unit length. {From R = ? l / A , ? = RA / L} Example 5: Calculate the resistanc e of a nichrome wire of length 500 mm and diameter 1. 0 mm, given that the resistivity of nichrome is 1. 1 x 10-6 ? m. Resistance, R = ? l / A = [(1. 1 x 10-6)(500 x 10-3)] / ? (1 x 10-3 / 2)2 = 0. 70 ? Electromotive force (Emf) is defined as the energy transferred / converted from non-electrical forms of energy into electrical energy when unit charge is moved round a complete circuit. ie EMF = Energy Transferred per unit charge E = WQEMF refers to the electrical energy generated from non-electrical energy forms, whereas PD refers to electrical energy being changed into non-electrical energy. For example, EMF Sources| Energy Change| PD across| Energy Change| Chemical Cell| Chem ; Elec| Bulb| Elec ; Light| Generator| Mech ; Elec| Fan| Elec ; Mech| Thermocouple| Thermal ; Elec| Door Bell| Elec ; Sound| Solar Cell| Solar ; Elec| Heating element| Elec ; Thermal| Effects of the internal resistance of a source of EMF: Internal resistance is the resistance to current flow within the power source.It reduces the potential difference (not EMF) across the terminal of the power supply when it is delivering a current. Consider the circuit below: The voltage across the resistor, V = IR, The voltage lost to internal resistance = Ir Thus, the EMF of the cell, E = IR + Ir = V + Ir Therefore If I = 0A or if r = 0? , V = E Motion in a Circle Kinematics of uniform circular motion Radian (rad) is the S. I. unit for angle, ? and it can be related to degrees in the following way. In one complete revolution, an object rotates through 360 ° , or 2? rad. As the object moves through an angle ? , with respect to the centre of rotation, this angle ? s known as the angular displacement. Angular velocity (? ) of the object is the rate of change of angular displacement with respect to time. ? = ? / t = 2? / T (for one complete revolution) Linear velocity, v, of an object is its instantaneous velocity at any point in its circular path. v = arc length / time taken = r? / t = r? * The directi on of the linear velocity is at a tangent to the circle described at that point. Hence it is sometimes referred to as the tangential velocity * ? is the same for every point in the rotating object, but the linear velocity v is greater for points further from the axis.A body moving in a circle at a constant speed changes velocity {since its direction changes}. Thus, it always experiences an acceleration, a force and a change in momentum. Centripetal acceleration a = r? 2 = v2 / r {in magnitude} Centripetal force Centripetal force is the resultant of all the forces that act on a system in circular motion. {It is not a particular force; â€Å"centripetal† means â€Å"centre-seeking†. Also, when asked to draw a diagram showing all the forces that act on a system in circular motion, it is wrong to include a force that is labelled as â€Å"centripetal force†. } Centripetal force, F = m r ? 2 = mv2 / r {in magnitude}A person in a satellite orbiting the Earth experience s â€Å"weightlessness† although the gravi field strength at that height is not zero because the person and the satellite would both have the same acceleration; hence the contact force between man ; satellite / normal reaction on the person is zero {Not because the field strength is negligible}. D. C. Circuits Circuit Symbols: Open Switch| Closed Switch| Lamp| Cell| Battery| Voltmeter| Resistor| Fuse| Ammeter| Variable resistor| Thermistor| Light dependent resistor (LDR)| Resistors in Series: R = R1 + R2 + †¦ Resistors in Parallel: 1/R = 1/R1 + 1/R2 + †¦ Example 1:Three resistors of resistance 2 ? , 3 ? and 4 ? respectively are used to make the combinations X, Y and Z shown in the diagrams. List the combinations in order of increasing resistance. Resistance for X = [1/2 + 1/(4+3)]-1 = 1. 56 ? Resistance for Y = 2 + (1/4 + 1/3)-1 = 3. 71 ? Resistance for Z = (1/3 + 1/2 + 1/4)-1 = 0. 923 ? Therefore, the combination of resistors in order of increasing resistance is Z X Y. Example: Referring to the circuit drawn, determine the value of I1, I and R, the combined resistance in the circuit. E = I1 (160) = I2 (4000) = I3 (32000) I1 = 2 / 160 = 0. 0125 A I2 = 2 / 4000 = 5 x 10-4 AI3 = 2 / 32000 = 6. 25 x 10-5 ASince I = I1 + I2 + I3, I = 13. 1 mAApplying Ohm’s Law, R = 213. 1 x 10-3 = 153 ? | | Example: A battery with an EMF of 20 V and an internal resistance of 2. 0 ? is connected to resistors R1 and R2 as shown in the diagram. A total current of 4. 0 A is supplied by the battery and R2 has a resistance of 12 ?. Calculate the resistance of R1 and the power supplied to each circuit component. E – I r = I2 R2 20 – 4 (2) = I2 (12) I2 = 1A Therefore, I1 = 4 – 1 = 3 AE – I r = I1 R1 12 = 3 R1 Therefore, R1 = 4Power supplied to R1 = (I1)2 R1 = 36 W Power supplied to R2 = (I2)2 R2 = 12 W| |For potential divider with 2 resistors in series, Potential drop across R1, V1 = R1 / (R1 + R2) x PD across R1 ; R2 Potential drop acro ss R2, V1 = R2 / (R1 + R2) x PD across R1 ; R2 Example: Two resistors, of resistance 300 k? and 500 k? respectively, form a potential divider with outer junctions maintained at potentials of +3 V and -15 V. Determine the potential at the junction X between the resistors. The potential difference across the 300 k? resistor = 300 / (300 + 500) [3 – (-15)] = 6. 75 V The potential at X = 3 – 6. 75 = -3. 75 V A thermistor is a resistor whose resistance varies greatly with temperature.Its resistance decreases with increasing temperature. It can be used in potential divider circuits to monitor and control temperatures. Example: In the figure on the right, the thermistor has a resistance of 800 ? when hot, and a resistance of 5000 ? when cold. Determine the potential at W when the temperature is hot. When thermistor is hot, potential difference across it = [800 / (800 + 1700)] x (7 – 2) = 1. 6 VThe potential at W = 2 + 1. 6 V = 3. 6 V| | A Light dependent resistor (LDR) is a resistor whose resistance varies with the intensity of light falling on it. Its resistance decreases with increasing light intensity.It can be used in a potential divider circuit to monitor light intensity. Example: In the figure below, the resistance of the LDR is 6. 0 M in the dark but then drops to 2. 0 k in the light Determine the potential at point P when the LDR is in the light. In the light the potential difference across the LDR= [2k / (3k + 2k)] x (18 – 3) = 6 VThe potential at P = 18 – 6= 12 V| | The potential difference along the wire is proportional to the length of the wire. The sliding contact will move along wire AB until it finds a point along the wire such that the galvanometer shows a zero reading.When the galvanometer shows a zero reading, the current through the galvanometer (and the device that is being tested) is zero and the potentiometer is said to be â€Å"balanced†. If the cell has negligible internal resistance, and if the potent iometer is balanced, EMF / PD of the unknown source, V = [L1 / (L1 + L2)] x E Example: In the circuit shown, the potentiometer wire has a resistance of 60 ?. Determine the EMF of the unknown cell if the balanced point is at B. Resistance of wire AB= [0. 65 / (0. 65 + 0. 35)] x 60 = 39 ? EMF of the test cell= [39 / (60 + 20)] x 12| Work, Energy and PowerWork Done by a force is defined as the product of the force and displacement (of its point of application) in the direction of the force W = F s cos ? Negative work is said to be done by F if x or its compo. is anti-parallel to F If a variable force F produces a displacement in the direction of F, the work done is determined from the area under F-x graph. {May need to find area by â€Å"counting the squares†. } By Principle of Conservation of Energy, Work Done on a system = KE gain + GPE gain + Work done against friction} Consider a rigid object of mass m that is initially at rest.To accelerate it uniformly to a speed v, a cons tant net force F is exerted on it, parallel to its motion over a displacement s. Since F is constant, acceleration is constant, Therefore, using the equation: v2 = u2 +2as, as = 12 (v2 – u2) Since kinetic energy is equal to the work done on the mass to bring it from rest to a speed v, The kinetic energy, EK| = Work done by the force F = Fs = mas = ? m (v2 – u2)| Gravitational potential energy: this arises in a system of masses where there are attractive gravitational forces between them.The gravitational potential energy of an object is the energy it possesses by virtue of its position in a gravitational field. Elastic potential energy: this arises in a system of atoms where there are either attractive or repulsive short-range inter-atomic forces between them. Electric potential energy: this arises in a system of charges where there are either attractive or repulsive electric forces between them. The potential energy, U, of a body in a force field {whether gravitationa l or electric field} is related to the force F it experiences by: F = – dU / dx.Consider an object of mass m being lifted vertically by a force F, without acceleration, from a certain height h1 to a height h2. Since the object moves up at a constant speed, F is equal to mg. The change in potential energy of the mass| = Work done by the force F = F s = F h = m g h| Efficiency: The ratio of (useful) output energy of a machine to the input energy. ie =| Useful Output Energy| x100% =| Useful Output Power| x100%| | Input Energy| | Input Power| | Power {instantaneous} is defined as the work done per unit time. P =| Total Work Done| =| W| | Total Time| | t|Since work done W = F x s, P =| F x s| =| Fv| | t| | | * for object moving at const speed: F = Total resistive force {equilibrium condition} * for object beginning to accelerate: F = Total resistive force + ma Forces Hooke's Law: Within the limit of proportionality, the extension produced in a material is directly proportional to the force/load applied F = kx Force constant k = force per unit extension (F/x) Elastic potential energy/strain energy = Area under the F-x graph {May need to â€Å"count the squares†} For a material that obeys Hooke? s law, Elastic Potential Energy, E = ? F x = ? x2 Forces on Masses in Gravitational Fields: A region of space in which a mass experiences an (attractive) force due to the presence of another mass. Forces on Charge in Electric Fields: A region of space where a charge experiences an (attractive or repulsive) force due to the presence of another charge. Hydrostatic Pressure p = ? gh {or, pressure difference between 2 points separated by a vertical distance of h } Upthrust: An upward force exerted by a fluid on a submerged or floating object; arises because of the difference in pressure between the upper and lower surfaces of the object.Archimedes' Principle: Upthrust = weight of the fluid displaced by submerged object. ie Upthrust = Volsubmerged x ? fluid x g Frict ional Forces: * The contact force between two surfaces = (friction2 + normal reaction2)? * The component along the surface of the contact force is called friction * Friction between 2 surfaces always opposes relative motion {or attempted motion}, and * Its value varies up to a maximum value {called the static friction} Viscous Forces: * A force that opposes the motion of an object in a fluid * Only exists when there is (relative) motion Magnitude of viscous force increases with the speed of the object Centre of Gravity of an object is defined as that pt through which the entire weight of the object may be considered to act. A couple is a pair of forces which tends to produce rotation only. Moment of a Force: The product of the force and the perpendicular distance of its line of action to the pivot Torque of a Couple: The produce of one of the forces of the couple and the perpendicular distance between the lines of action of the forces. (WARNING: NOT an action-reaction pair as they a ct on the same body. ) Conditions for Equilibrium (of an extended object): 1.The resultant force acting on it in any direction equals zero 2. The resultant moment about any point is zero If a mass is acted upon by 3 forces only and remains in equilibrium, then 1. The lines of action of the 3 forces must pass through a common point 2. When a vector diagram of the three forces is drawn, the forces will form a closed triangle (vector triangle), with the 3 vectors pointing in the same orientation around the triangle. Principle of Moments: For a body to be in equilibrium, the sum of all the anticlockwise moments about any point must be equal to the sum of all the clockwise moments about that same point.Measurement Base quantities and their units; mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol): Base Quantities| SI Units| | Name| Symbol| Length| metre| m| Mass| kilogram| kg| Time| second| s| Amount of substance| mole| mol| Temperature| Kelvin| K| C urrent| ampere| A| Luminous intensity| candela| cd| Derived units as products or quotients of the base units: Derived| Quantities Equation| Derived Units| Area (A)| A = L2| m2| Volume (V)| V = L3| m3| Density (? )| ? = m / V| kg m-3| Velocity (v)| v = L / t| ms-1| Acceleration (a)| a = ? v / t| ms-1 / s = ms-2|Momentum (p)| p = m x v| (kg)(ms-1) = kg m s-1| Derived Quantities| Equation| Derived Unit| Derived Units| | | Special Name| Symbol| | Force (F)| F = ? p / t| Newton| N| [(kg m s-1) / s = kg m s-2| Pressure (p)| p = F / A| Pascal| Pa| (kg m s-2) / m2 = kg m-1 s-2| Energy (E)| E = F x d| joule| J| (kg m s-2)(m) = kg m2 s-2| Power (P)| P = E / t| watt| W| (kg m2 s-2) / s = kg m2 s-3| Frequency (f)| f = 1 / t| hertz| Hz| 1 / s = s-1| Charge (Q)| Q = I x t| coulomb| C| A s| Potential Difference (V)| V = E / Q| volt| V| (kg m2 s-2) / A s = kg m2 s-3 A-1| Resistance (R)| R = V / I| ohm| ? (kg m2 s-3 A-1) / A = kg m2 s-3 A-2| Prefixes and their symbols to indicate decimal sub-multipl es or multiples of both base and derived units: Multiplying Factor| Prefix| Symbol| 10-12| pico| p| 10-9| nano| n| 10-6| micro| ? | 10-3| milli| m| 10-2| centi| c| 10-1| decid| d| 103| kilo| k| 106| mega| M| 109| giga| G| 1012| tera| T| Estimates of physical quantities: When making an estimate, it is only reasonable to give the figure to 1 or at most 2 significant figures since an estimate is not very precise. Physical Quantity| Reasonable Estimate| Mass of 3 cans (330 ml) of Coke| 1 kg|Mass of a medium-sized car| 1000 kg| Length of a football field| 100 m| Reaction time of a young man| 0. 2 s| * Occasionally, students are asked to estimate the area under a graph. The usual method of counting squares within the enclosed area is used. (eg. Topic 3 (Dynamics), N94P2Q1c) * Often, when making an estimate, a formula and a simple calculation may be involved. EXAMPLE 1: Estimate the average running speed of a typical 17-year-old? s 2. 4-km run. velocity = distance / time = 2400 / (12. 5 x 60) = 3. 2 ? 3 ms-1 EXAMPLE 2: Which estimate is realistic? | Option| Explanation|A| The kinetic energy of a bus travelling on an expressway is 30000J| A bus of mass m travelling on an expressway will travel between 50 to 80 kmh-1, which is 13. 8 to 22. 2 ms-1. Thus, its KE will be approximately ? m(182) = 162m. Thus, for its KE to be 30000J: 162m = 30000. Thus, m = 185kg, which is an absurd weight for a bus; ie. This is not a realistic estimate. | B| The power of a domestic light is 300W. | A single light bulb in the house usually runs at about 20W to 60W. Thus, a domestic light is unlikely to run at more than 200W; this estimate is rather high. | C| The temperature of a hot oven is 300 K. 300K = 27 0C. Not very hot. | D| The volume of air in a car tyre is 0. 03 m3. | | Estimating the width of a tyre, t, is 15 cm or 0. 15 m, and estimating R to be 40 cm and r to be 30 cm,volume of air in a car tyre is = ? (R2 – r2)t = ? (0. 42 – 0. 32)(0. 15) = 0. 033 m3 ? 0. 03 m3 (t o one sig. fig. )| Distinction between systematic errors (including zero errors) and random errors and between precision and accuracy: Random error: is the type of error which causes readings to scatter about the true value. Systematic error: is the type of error which causes readings to deviate in one direction from the true value.Precision: refers to the degree of agreement (scatter, spread) of repeated measurements of the same quantity. {NB: regardless of whether or not they are correct. } Accuracy: refers to the degree of agreement between the result of a measurement and the true value of the quantity. | ; ; R Error Higher ; ; ; ; ; ; Less Precise ; ; ;| v v vS Error HigherLess Accuratev v v| | | | | | Assess the uncertainty in a derived quantity by simple addition of actual, fractional or percentage uncertainties (a rigorous statistical treatment is not required). For a quantity x = (2. 0  ± 0. 1) mm,Actual/ Absolute uncertainty, ? x =  ± 0. 1 mm Fractional uncertainty, ? x x = 0. 05 Percentage uncertainty, ? xx 100% = 5 % If p = (2x + y) / 3 or p = (2x – y) / 3, ? p = (2? x + ? y) / 3 If r = 2xy3 or r = 2x / y3, ? r / r = ? x / x + 3? y / y Actual error must be recorded to only 1 significant figure, ; The number of decimal places a calculated quantity should have is determined by its actual error. For eg, suppose g has been initially calculated to be 9. 80645 ms-2 ; ? g has been initially calculated to be 0. 04848 ms-2. The final value of ? g must be recorded as 0. 5 ms-2 {1 sf }, and the appropriate recording of g is (9. 81  ± 0. 05) ms-2. Distinction between scalar and vector quantities: | Scalar| Vector| Definition| A scalar quantity has a magnitude only. It is completely described by a certain number and a unit. | A vector quantity has both magnitude and direction. It can be described by an arrow whose length represents the magnitude of the vector and the arrow-head represents the direction of the vector. | Examples| Distance, speed, mass , time, temperature, work done, kinetic energy, pressure, power, electric charge etc. Common Error:Students tend to associate kinetic energy and pressure with vectors because of the vector components involved. However, such considerations have no bearings on whether the quantity is a vector or scalar. | Displacement, velocity, moments (or torque), momentum, force, electric field etc. | Representation of vector as two perpendicular components: In the diagram below, XY represents a flat kite of weight 4. 0 N. At a certain instant, XY is inclined at 30 ° to the horizontal and the wind exerts a steady force of 6. 0 N at right angles to XY so that the kite flies freely.By accurate scale drawing| By calculations using sine and cosine rules, or Pythagoras? theorem| Draw a scale diagram to find the magnitude and direction of the resultant force acting on the kite. R = 3. 2 N (? 3. 2 cm) at ? = 112 ° to the 4 N vector. | Using cosine rule, a2 = b2 + c2 – 2bc cos A R2 = 42 + 62 -2( 4)(6)(cos 30 °) R = 3. 23 NUsing sine rule: a / sin A = b / sin B 6 / sin ? = 3. 23 / sin 30 ° ? = 68 ° or 112 ° = 112 ° to the 4 N vector| Summing Vector Components| | Fx = – 6 sin 30 ° = – 3 NFy = 6 cos 30 ° – 4 = 1. 2 NR = v(-32 + 1. 22) = 3. 23 Ntan ? = 1. 2 / 3 = 22 °R is at an angle 112 ° to the 4 N vector. (90 ° + 22 °)|Kinematics Displacement, speed, velocity and acceleration: Distance: Total length covered irrespective of the direction of motion. Displacement: Distance moved in a certain direction. Speed: Distance travelled per unit time. Velocity: is defined as the rate of change of displacement, or, displacement per unit time {NOT: displacement over time, nor, displacement per second, nor, rate of change of displacement per unit time} Acceleration: is defined as the rate of change of velocity. Using graphs to find displacement, velocity and acceleration: * The area under a velocity-time graph is the change in displacement. The gr adient of a displacement-time graph is the {instantaneous} velocity. * The gradient of a velocity-time graph is the acceleration. The ‘SUVAT' Equations of Motion The most important word for this chapter is SUVAT, which stands for: * S (displacement), * U (initial velocity), * V (final velocity), * A (acceleration) and * T (time) of a particle that is in motion. Below is a list of the equations you MUST memorise, even if they are in the formula book, memorise them anyway, to ensure you can implement them quickly. 1. v = u +at| derived from definition of acceleration: a = (v – u) / t| 2. | s = ? (u + v) t| derived from the area under the v-t graph| 3. | v2 = u2 + 2as| derived from equations (1) and (2)| 4. | s = ut + ? at2| derived from equations (1) and (2)| These equations apply only if the motion takes place along a straight line and the acceleration is constant; {hence, for eg. , air resistance must be negligible. } Motion of bodies falling in a uniform gravitational field with air resistance: Consider a body moving in a uniform gravitational field under 2 different conditions: Without Air Resistance:Assuming negligible air resistance, whether the body is moving up, or at the highest point or moving down, the weight of the body, W, is the only force acting on it, causing it to experience a constant acceleration. Thus, the gradient of the v-t graph is constant throughout its rise and fall. The body is said to undergo free fall. With Air Resistance: If air resistance is NOT negligible and if it is projected upwards with the same initial velocity, as the body moves upwards, both air resistance and weight act downwards. Thus its speed will decrease at a rate greater than . 81 ms-2 . This causes the time taken to reach its maximum height reached to be lower than in the case with no air resistance. The max height reached is also reduced. At the highest point, the body is momentarily at rest; air resistance becomes zero and hence the only force acting on it is the weight. The acceleration is thus 9. 81 ms-2 at this point. As a body falls, air resistance opposes its weight. The downward acceleration is thus less than 9. 81 ms-2. As air resistance increases with speed, it eventually equals its weight (but in opposite direction).From then there will be no resultant force acting on the body and it will fall with a constant speed, called the terminal velocity. Equations for the horizontal and vertical motion: | x direction (horizontal – axis)| y direction (vertical – axis)| s (displacement)| sx = ux t sx = ux t + ? ax t2| sy = uy t + ? ay t2 (Note: If projectile ends at same level as the start, then sy = 0)| u (initial velocity)| ux| uy| v (final velocity)| vx = ux + axt (Note: At max height, vx = 0)| vy = uy + at vy2 = uy2 + 2asy| a (acceleration)| ax (Note: Exists when a force in x direction present)| ay (Note: If object is falling, then ay = -g)| (time)| t| t| Parabolic Motion: tan ? = vy / vx ?: direction of tangenti al velocity {NOT: tan ? = sy / sx } Forces Hooke's Law: Within the limit of proportionality, the extension produced in a material is directly proportional to the force/load applied F = kx Force constant k = force per unit extension (F/x) Elastic potential energy/strain energy = Area under the F-x graph {May need to â€Å"count the squares†} For a material that obeys Hooke? s law, Elastic Potential Energy, E = ? F x = ? k x2 Forces on Masses in Gravitational Fields: A region of space in which a mass experiences an (attractive) force due to the presence of another mass.Forces on Charge in Electric Fields: A region of space where a charge experiences an (attractive or repulsive) force due to the presence of another charge. Hydrostatic Pressure p = ? gh {or, pressure difference between 2 points separated by a vertical distance of h } Upthrust: An upward force exerted by a fluid on a submerged or floating object; arises because of the difference in pressure between the upper and l ower surfaces of the object. Archimedes' Principle: Upthrust = weight of the fluid displaced by submerged object. ie Upthrust = Volsubmerged x ? fluid x g Frictional Forces: The contact force between two surfaces = (friction2 + normal reaction2)? * The component along the surface of the contact force is called friction * Friction between 2 surfaces always opposes relative motion {or attempted motion}, and * Its value varies up to a maximum value {called the static friction} Viscous Forces: * A force that opposes the motion of an object in a fluid * Only exists when there is (relative) motion * Magnitude of viscous force increases with the speed of the object Centre of Gravity of an object is defined as that pt through which the entire weight of the object may be considered to act.A couple is a pair of forces which tends to produce rotation only. Moment of a Force: The product of the force and the perpendicular distance of its line of action to the pivot Torque of a Couple: The produ ce of one of the forces of the couple and the perpendicular distance between the lines of action of the forces. (WARNING: NOT an action-reaction pair as they act on the same body. ) Conditions for Equilibrium (of an extended object): 1. The resultant force acting on it in any direction equals zero 2. The resultant moment about any point is zero If a mass is acted upon by 3 forces only and remains in equilibrium, then 1.The lines of action of the 3 forces must pass through a common point 2. When a vector diagram of the three forces is drawn, the forces will form a closed triangle (vector triangle), with the 3 vectors pointing in the same orientation around the triangle. Principle of Moments: For a body to be in equilibrium, the sum of all the anticlockwise moments about any point must be equal to the sum of all the clockwise moments about that same point. Work, Energy and Power Work Done by a force is defined as the product of the force and displacement (of its point of application) in the direction of the force W = F s cos ?Negative work is said to be done by F if x or its compo. is anti-parallel to F If a variable force F produces a displacement in the direction of F, the work done is determined from the area under F-x graph. {May need to find area by â€Å"counting the squares†. } By Principle of Conservation of Energy, Work Done on a system = KE gain + GPE gain + Work done against friction} Consider a rigid object of mass m that is initially at rest. To accelerate it uniformly to a speed v, a constant net force F is exerted on it, parallel to its motion over a displacement s. Since F is constant, acceleration is constant, Therefore, using the equation: 2 = u2 +2as, as = 12 (v2 – u2) Since kinetic energy is equal to the work done on the mass to bring it from rest to a speed v, The kinetic energy, EK| = Work done by the force F = Fs = mas = ? m (v2 – u2)| Gravitational potential energy: this arises in a system of masses where there are at tractive gravitational forces between them. The gravitational potential energy of an object is the energy it possesses by virtue of its position in a gravitational field. Elastic potential energy: this arises in a system of atoms where there are either attractive or repulsive short-range inter-atomic forces between them.Electric potential energy: this arises in a system of charges where there are either attractive or repulsive electric forces between them. The potential energy, U, of a body in a force field {whether gravitational or electric field} is related to the force F it experiences by: F = – dU / dx. Consider an object of mass m being lifted vertically by a force F, without acceleration, from a certain height h1 to a height h2. Since the object moves up at a constant speed, F is equal to mg. The change in potential energy of the mass| = Work done by the force F = F s = F h = m g h|Efficiency: The ratio of (useful) output energy of a machine to the input energy. ie =| U seful Output Energy| x100% =| Useful Output Power| x100%| | Input Energy| | Input Power| | Power {instantaneous} is defined as the work done per unit time. P =| Total Work Done| =| W| | Total Time| | t| Since work done W = F x s, P =| F x s| =| Fv| | t| | | * for object moving at const speed: F = Total resistive force {equilibrium condition} * for object beginning to accelerate: F = Total resistive force + ma Wave Motion Displacement (y): Position of an oscillating particle from its equilibrium position.Amplitude (y0 or A): The maximum magnitude of the displacement of an oscillating particle from its equilibrium position. Period (T): Time taken for a particle to undergo one complete cycle of oscillation. Frequency (f): Number of oscillations performed by a particle per unit time. Wavelength (? ): For a progressive wave, it is the distance between any two successive particles that are in phase, e. g. it is the distance between 2 consecutive crests or 2 troughs. Wave speed (v): The sp eed at which the waveform travels in the direction of the propagation of the wave.Wave front: A line or surface joining points which are at the same state of oscillation, i. e. in phase, e. g. a line joining crest to crest in a wave. Ray: The path taken by the wave. This is used to indicate the direction of wave propagation. Rays are always at right angles to the wave fronts (i. e. wave fronts are always perpendicular to the direction of propagation). From the definition of speed, Speed = Distance / Time A wave travels a distance of one wavelength, ? , in a time interval of one period, T. The frequency, f, of a wave is equal to 1 / T Therefore, speed, v = ? / T = (1 / T)? f? v = f? Example 1: A wave travelling in the positive x direction is showed in the figure. Find the amplitude, wavelength, period, and speed of the wave if it has a frequency of 8. 0 Hz. Amplitude (A) = 0. 15 mWavelength (? ) = 0. 40 mPeriod (T) = 1f = 18. 0 ? 0. 125 sSpeed (v) =f? = 8. 0 x 0. 40 = 3. 20 m s-1A wa ve which results in a net transfer of energy from one place to another is known as a progressive wave. | | Intensity {of a wave}: is defined as the rate of energy flow per unit time {power} per unit cross-sectional area perpendicular to the direction of wave propagation.Intensity = Power / Area = Energy / (Time x Area) For a point source (which would emit spherical wavefronts), Intensity = (? m? 2xo2) / (t x 4? r2) where x0: amplitude ; r: distance from the point source. Therefore, I ? xo2 / r2 (Pt Source) For all wave sources, I ? (Amplitude)2 Transverse wave: A wave in which the oscillations of the wave particles {NOT: movement} are perpendicular to the direction of the propagation of the wave. Longitudinal wave: A wave in which the oscillations of the wave particles are parallel to the direction of the propagation of the wave.Polarisation is said to occur when oscillations are in one direction in a plane, {NOT just â€Å"in one direction†} normal to the direction of propag ation. {Only transverse waves can be polarized; longitudinal waves can’t. }Example 2: The following stationary wave pattern is obtained using a C. R. O. whose screen is graduated in centimetre squares. Given that the time-base is adjusted such that 1 unit on the horizontal axis of the screen corresponds to a time of 1. 0 ms, find the period and frequency of the wave. Period, T = (4 units) x 1. 0 = 4. 0 ms = 4. 0 x 10-3 sf = 1 / T = 14 x 10-3 250 Hz| | Superposition Principle of Superposition: When two or more waves of the same type meet at a point, the resultant displacement of the waves is equal to the vector sum of their individual displacements at that point. Stretched String A horizontal rope with one end fixed and another attached to a vertical oscillator. Stationary waves will be produced by the direct and reflected waves in the string. Or we can have the string stopped at one end with a pulley as shown below. Microwaves A microwave emitter placed a distance away from a metal plate that reflects the emitted wave.By moving a detector along the path of the wave, the nodes and antinodes could be detected. Air column A tuning fork held at the mouth of a open tube projects a sound wave into the column of air in the tube. The length of the tube can be changed by varying the water level. At certain lengths of the tube, the air column resonates with the tuning fork. This is due to the formation of stationary waves by the incident and reflected sound waves at the water surface. Stationary (Standing) Wave) is one * whose waveform/wave profile does not advance {move}, where there is no net transport of energy, and * where the positions of antinodes and nodes do not change (with time). A stationary wave is formed when two progressive waves of the same frequency, amplitude and speed, travelling in opposite directions are superposed. {Assume boundary conditions are met} | Stationary waves| Stationary Waves Progressive Waves| Amplitude| Varies from maximum at th e anti-nodes to zero at the nodes. | Same for all particles in the wave (provided no energy is lost). | Wavelength| Twice the distance between a pair of adjacent nodes or anti-nodes. The distance between two consecutive points on a wave, that are in phase. | Phase| Particles in the same segment/ between 2 adjacent nodes, are in phase. Particles in adjacent segments are in anti-phase. | All particles within one wavelength have different phases. | Wave Profile| The wave profile does not advance. | The wave profile advances. | Energy| No energy is transported by the wave. | Energy is transported in the direction of the wave. | Node is a region of destructive superposition where the waves always meet out of phase by ? radians. Hence displacement here is permanently zero {or minimum}.Antinode is a region of constructive superposition where the waves always meet in phase. Hence a particle here vibrates with maximum amplitude {but it is NOT a pt with a permanent large displacement! } Dist between 2 successive nodes / antinodes = ? / 2 Max pressure change occurs at the nodes {NOT the antinodes} because every node changes fr being a pt of compression to become a pt of rarefaction {half a period later} Diffraction: refers to the spreading {or bending} of waves when they pass through an opening {gap}, or round an obstacle (into the â€Å"shadow† region). Illustrate with diag} For significant diffraction to occur, the size of the gap ? ? of the wave For a diffraction grating, d sin ? = n ? , d = dist between successive slits {grating spacing} = reciprocal of number of lines per metre When a â€Å"white light† passes through a diffraction grating, for each order of diffraction, a longer wavelength {red} diffracts more than a shorter wavelength {violet} {as sin ? ? ? }. Diffraction refers to the spreading of waves as they pass through a narrow slit or near an obstacle. For diffraction to occur, the size of the gap should approximately be equal to the wavelengt h of the wave.Coherent waves: Waves having a constant phase difference {not: zero phase difference / in phase} Interference may be described as the superposition of waves from 2 coherent sources. For an observable / well-defined interference pattern, the waves must be coherent, have about the same amplitude, be unpolarised or polarised in the same direction, ; be of the same type. Two-source interference using: 1. Water Waves Interference patterns could be observed when two dippers are attached to the vibrator of the ripple tank.The ripples produce constructive and destructive interference. The dippers are coherent sources because they are fixed to the same vibrator. 2. Microwaves Microwave emitted from a transmitter through 2 slits on a metal plate would also produce interference patterns. By moving a detector on the opposite side of the metal plate, a series of rise and fall in amplitude of the wave would be registered. 3. Light Waves (Young? s double slit experiment) Since light is emitted from a bulb randomly, the way to obtain two coherent light sources is by splitting light from a single slit.The 2 beams from the double slit would then interfere with each other, creating a pattern of alternate bright and dark fringes (or high and low intensities) at regular intervals, which is also known as our interference pattern. Condition for Constructive Interference at a pt P: Phase difference of the 2 waves at P = 0 {or 2? , 4? , etc} Thus, with 2 in-phase sources, * implies path difference = n? ; with 2 antiphase sources: path difference = (n + ? )? Condition for Destructive Interference at a pt P: Phase difference of the 2 waves at P = ? { or 3? , 5? , etc } With 2 in-phase sources, + implies path difference = (n+ ? ), with 2 antiphase sources: path difference = n ? Fringe separation x = ? D / a, if a;;D {applies only to Young's Double Slit interference of light, ie, NOT for microwaves, sound waves, water waves} Phase difference betw the 2 waves at any pt X {be tw the central & 1st maxima) is (approx) proportional to the dist of X from the central maxima. Using 2 sources of equal amplitude x0, the resultant amplitude of a bright fringe would be doubled {2Ãâ€"0}, & the resultant intensity increases by 4 times {not 2 times}. { IResultant ? (2 x0)2 } Electric FieldsElectric field strength / intensity at a point is defined as the force per unit positive charge acting at that point {a vector; Unit: N C-1 or V m-1} E = F / q > F = qE * The electric force on a positive charge in an electric field is in the direction of E, while * The electric force on a negative charge is opposite to the direction of E. * Hence a +ve charge placed in an electric field will accelerate in the direction of E and gain KE {& simultaneously lose EPE}, while a negative charge caused to move (projected) in the direction of E will decelerate, ie lose KE, { & gain EPE}. Representation of electric fields by field lines | | | | | Coulomb's law: The (mutual) electric force F acting between 2 point charges Q1 and Q2 separated by a distance r is given by: F = Q1Q2 / 4 or2 where ? 0: permittivity of free space or, the (mutual) electric force between two point charges is proportional to the product of their charges ; inversely proportional to the square of their separation. Example 1: Two positive charges, each 4. 18 ? C, and a negative charge, -6. 36 ? C, are fixed at the vertices of an equilateral triangle of side 13. 0 cm. Find the electrostatic force on the negative charge. | F = Q1Q2 / 4 or2= (8. 99 x 109) [(4. 18 x 10-6)(6. 6 x 10-6) / (13. 0 x 10-2)2]= 14. 1 N (Note: negative sign for -6. 36 ? C has been ignored in the calculation)FR = 2 x Fcos300= 24. 4 N, vertically upwards| Electric field strength due to a Point Charge Q : E = Q / 4 or2 {NB: Do NOT substitute a negative Q with its negative sign in calculations! } Example 2: In the figure below, determine the point (other than at infinity) at which the total electric field strength is zero. From t he diagram, it can be observed that the point where E is zero lies on a straight line where the charges lie, to the left of the -2. 5 ? C charge. Let this point be a distance r from the left charge.Since the total electric field strength is zero, E6? = E-2? [6? / (1 + r)2] / 4 or2 = [2. 5? / r2] / 4 or2 (Note: negative sign for -2. 5 ? C has been ignored here) 6 / (1 + r)2 = 2. 5 / r2 v(6r) = 2. 5 (1 + r) r = 1. 82 m The point lies on a straight line where the charges lie, 1. 82 m to the left of the -2. 5 ? C charge. Uniform electric field between 2 Charged Parallel Plates: E = Vd, d: perpendicular dist between the plates, V: potential difference between plates Path of charge moving at 90 ° to electric field: parabolic. Beyond the pt where it exits the field, the path is a straight line, at a tangent to the parabola at exit.Example 3: An electron (m = 9. 11 x 10-31 kg; q = -1. 6 x 10-19 C) moving with a speed of 1. 5 x 107 ms-1, enters a region between 2 parallel plates, which are 20 mm apart and 60 mm long. The top plate is at a potential of 80 V relative to the lower plate. Determine the angle through which the electron has been deflected as a result of passing through the plates. Time taken for the electron to travel 60 mm horizontally = Distance / Speed = 60 x 10-3 / 1. 5 x 107 = 4 x 10-9 s E = V / d = 80 / 20 x 10-3 = 4000 V m-1 a = F / m = eE / m = (1. 6 x 10-19)(4000) / (9. 1 x 10-31) = 7. 0 x 1014 ms-2 vy = uy + at = 0 + (7. x 1014)( 4 x 10-9) = 2. 8 x 106 ms-1 tan ? = vy / vx = 2. 8 x 106 / 1. 5 x 107 = 0. 187 Therefore ? = 10. 6 ° Effect of a uniform electric field on the motion of charged particles * Equipotential surface: a surface where the electric potential is constant * Potential gradient = 0, ie E along surface = 0 } * Hence no work is done when a charge is moved along this surface. { W=QV, V=0 } * Electric field lines must meet this surface at right angles. * {If the field lines are not at 90 ° to it, it would imply that there is a non- zero component of E along the surface. This would contradict the fact that E along an equipotential = 0. Electric potential at a point: is defined as the work done in moving a unit positive charge from infinity to that point, { a scalar; unit: V } ie V = W / Q The electric potential at infinity is defined as zero. At any other point, it may be positive or negative depending on the sign of Q that sets up the field. {Contrast gravitational potential. } Relation between E and V: E = – dV / dr i. e. The electric field strength at a pt is numerically equal to the potential gradient at that pt. NB: Electric field lines point in direction of decreasing potential {ie from high to low pot}.Electric potential energy U of a charge Q at a pt where the potential is V: U = QV Work done W on a charge Q in moving it across a pd ? V: W = Q ? V Electric Potential due to a point charge Q : V = Q / 4 or {NB: Substitute Q with its sign} Electromagnetism When a conductor carrying a current is plac ed in a magnetic field, it experiences a magnetic force. The figure above shows a wire of length L carrying a current I and lying in a magnetic field of flux density B. Suppose the angle between the current I and the field B is ? , the magnitude of the force F on the conductor is iven by F = BILsin? The direction of the force can be found using Fleming? s Left Hand Rule (see figure above). Note that the force is always perpendicular to the plane containing both the current I and the magnetic field B. * If the wire is parallel to the field lines, then ? = 0 °, and F = 0. (No magnetic force acts on the wire) * If the wire is at right angles to the field lines, then ? = 90 °, and the magnetic force acting on the wire would be maximum (F = BIL) Example The 3 diagrams below each show a magnetic field of flux density 2 T that lies in the plane of the page.In each case, a current I of 10 A is directed as shown. Use Fleming's Left Hand Rule to predict the directions of the forces and wo rk out the magnitude of the forces on a 0. 5 m length of wire that carries the current. (Assume the horizontal is the current) | | | F = BIL sin? = 2 x 10 x 0. 5 x sin90 = 10 N| F = BIL sin? = 2 x 10 x 0. 5 x sin60 = 8. 66 N| F = BIL sin ? = 2 x 10 x 0. 5 x sin180 = 0 N| Magnetic flux density B is defined as the force acting per unit current in a wire of unit length at right-angles to the field B = F / ILsin ? > F = B I L sin ? {? Angle between the B and L} {NB: write down the above defining equation & define each symbol if you're not able to give the â€Å"statement form†. } Direction of the magnetic force is always perpendicular to the plane containing the current I and B {even if ? ? 0} The Tesla is defined as the magnetic flux density of a magnetic field that causes a force of one newton to act on a current of one ampere in a wire of length one metre which is perpendicular to the magnetic field. By the Principle of moments, Clockwise moments = Anticlockwise moments mg â⠂¬ ¢ x = F †¢ y = BILsin90 †¢ yB = mgx / ILy Example A 100-turn rectangular coil 6. 0 cm by 4. 0 cm is pivoted about a horizontal axis as shown below. A horizontal uniform magnetic field of direction perpendicular to the axis of the coil passes through the coil. Initially, no mass is placed on the pan and the arm is kept horizontal by adjusting the counter-weight. When a current of 0. 50 A flows through the coil, equilibrium is restored by placing a 50 mg mass on the pan, 8. 0 cm from the pivot. Determine the magnitude of the magnetic flux density and the direction of the current in the coil.Taking moments about the pivot, sum of Anti-clockwise moments = Clockwise moment (2 x n)(FB) x P = W x Q (2 x n)(B I L) x P = m g x Q, where n: no. of wires on each side of the coil (2 x 100)(B x 0. 5 x 0. 06) x 0. 02 = 50 x 10

Nursing Situation Essay Example | Topics and Well Written Essays - 250 words

Nursing Situation - Essay Example For instance, during my internship period in the hospital, I happened to witness one such incident where a comatose patient needed to be fed through a nasogastric tube every three hours according to the feeding regime posted above the patient’s bed. The whole day’s feeds were still intact, and it was already past 4pm in the afternoon. The relatives of the patient just sat next to the bed as they did not know how to feed their loved one through the tube. A look at the patient’s blood glucose levels showed alarming results since the patient was starving and would die if he was not fed immediately. This showed gross misconduct of the nurses and went against the theory of Nursing as caring as described by Watson (Hills & Watson 256). The theory was made on the assumption that persons, in this case nurses, are caring by virtue of their humanness. All in all, I learnt that all it could have taken to relieve the patient’s suffering and increase chances of recovery was to feed the patient on time. If we can all perform our duties as required, it would help to prevent unnecessary deaths in

The Worldliness of English in Saudi Arabia Dissertation

The Worldliness of English in Saudi Arabia - Dissertation Example Researchers who look at the spread of English as mere linguistic imperialism question the enterprise of learning and teaching of the English language. This is because, from their viewpoint, it has the cultural integrity of the non-native speaker compromised. In order for a language instructor to come into terms with the imposition of English language learning culturally is to utilize the practices of ELT that define and position English as an international language (EIL). In my point of view, the alternative perpetuates the negative impact that learning a foreign language can pose to the cultural integrity of the learner. Linguistic imperialism is a concept of linguistics involving a transfer, to other people, of a dominant language. This transfer is often associated with power demonstration. This could be military power or even economic power. Dominant cultures are often transferred together with the language. According to Brutt-Griffler (2002), the theory of linguistic imperialism has magnetized much attention among applied linguistic scholars. This has resulted in much debate especially on the shortcomings and merits of the theory. Brutt-Griffler stated linguistic imperialism denunciations to the analyses of English as the language of world domination and world capitalism. Generally, linguistic imperialism is usually viewed in the perspective of cultural imperialism.  

Why patient satisfaction is important economically Essay

Why patient satisfaction is important economically - Essay Example The first objective is to come up with data of patient’s perspective of care that will help obtain what is important to the customers. The second objective is to create report that will help hospitals improve their service care. The third objective is to come up with public report to enhance accountability, transparency and quality of care out of the public investment made. It is therefore clear that there is indeed an attempt to improve or achieve patient satisfaction in health care. It is therefore essential to understand that in health care, it is not just important to consider generation of profit, but from an economic perspective patient satisfaction should be above all. Patients: Sources of health care providers’ income Patients are the ones who are served by various health care providers. Patients help the latter to generate their income. Thus, there are various economic incentives that help to achieve or generate user satisfaction. One of these incentives is on quality of professional life that tries to encourage physicians to realize their burden for their patients. However, this move is said to only increase the expectations of health care professionals to long for strong structure of management support that may only end up giving negative impact on the user’s satisfaction (Badia et al., 2007).

Everyday uses of mathematics 0920 Essay Example | Topics and Well Written Essays - 500 words

Everyday uses of mathematics 0920 - Essay Example One simply cannot cook unless one is not able to get the proportion of varied ingredients that need to be put in a particular dish. One cannot cook varied recipes given in cook books and magazines if one does not know the basic mathematics to be able to calculate the quantity of varied spices and ingredients that one needs to put in a dish one is cooking. Once again, driving a car is a fairly common activity. Yet, the thing is that to know as to when one will reach one’s destination one need to know about the distance at which a place is located and the speed of one’s car. Only then one is able to calculate the time when he will reach the intended destination. Once again, this requires knowledge of basic mathematics. Students and household people do keep weekly and monthly budgets to keep an eye on their expenditure and savings. Again it is not possible to make and manage household budgets unless one does not know how to count the money one has at one’s disposal and as to how to add, subtract, divide and multiply varied sums of money. The one other thing students and professionals do is to keep a weekly and monthly planner to be able to manage their routines and to keep an eye on the time they have at their disposal. Again, one really cannot keep oneself organized and punctual by keeping a track of one’s t ime if one does not know how to watch time and the basic mathematics to be able to add and subtract time. The other commonly known activity that requires the knowledge of mathematics is the maintenance of personal statistics. People losing weight do keep a track of the pounds they have gained or lost and the change in the circumference of their waist and arms and legs. One really cannot do these things without knowing a little bit of mathematics. Isn’t it interesting to note that one even cannot lose weight without having knowledge of mathematics? People often go to shopping and while

Your task is to develop a model which could be used to inform an Essay

Your task is to develop a model which could be used to inform an economic evaluation - Essay Example It can be seen that the maximum amount of money is spend on the diagnostic procedure- echocardiogram. Around 142.16 $ is spend for this. Then the model included other primary evaluations in health care for the particular disease as ECG, TFT, INR, FBC, coagulation studies and medication. The total cost incurred for the primary visit is 418. 08. There have been reviews on the increased cost of ECG on adolescents and neonates. It is estimated that cost effectiveness was at peak between [,000 in 14 year olds and $ 204000 in screening done in 8 year children for the life saved per year. (Saul, Samuel & Gidding 2014). Both warfarin and aspirin are anti-coagulants, which are administered to prevent the clot formation in the blood vessels of heart, which may lead to cardiovascular diseases. Warfarin and aspirin were administered in patients at risk of developing heart problems. Risk category included obese patients, patients with diabetes mellitus. It may seen that, the cost spent for visit of general practitioner without the administration of any medication and with the prescription of aspirin was the same (552,992 $). The cost spent for speciality visit was same for all three categories. The use of diagnostic procedures like ECG and Echocardiogram spent the same amount. The amount of money spent on TFT is same for all the three categories. No amount of money was additionally spent on INR, FBC, and coagulation studies on the administration of aspirin and warfarin. When the total cost was estimated along with the administration of medication and frequency of use, less amount of money was spent when aspirin was used for prevention. After deploying this model for three years, the end result was found use of aspirin prevented the occurrence of cardiovascular diseases in comparison with administration of warfarin and without any intervention. This indicates that this model may be used in the prevention of

Operation Management Essay Example | Topics and Well Written Essays - 2500 words - 1

Operation Management - Essay Example The QMS shall also provide the parameters for quality service while performance monitoring of each of the processes shall be through the process’ key performance indicators. Any flaw or parameter that fails to satisfy the accepted threshold of the performance indicator shall be subject to a root cause analysis to determine a corrective or preventive solution. The QMS requires regular review to ensure that the organization remains focus and faithful to its objective. The hotel employee’s performance shall be subject to evaluation by using the key performance indicator’s root cause analysis. For QMS, the hotel guest’s or patron’s feedback, comment or opinion is accorded greater weight as it will not only change how the hotel will conduct its business but it will equally show how the hotel value their guest’s and patron’s point of view with regard to the hotel’s operation. ... The marriage of technology and human ingenuity are very much apparent in the hotel industry by deploying an Enterprise Resource Planning system. As applied to the hotel industry, it would ensure excellent customer experience from their reservation up to their next visit. The deployment of a Customer Relationship Management System would ensure that all issues are addressed and monitored and shall similarly ensure that the business is properly guided on how to become customer centric. However, technology will not work on its own as its success will be dependent on the employees who use the system and those who will execute the work instructions recommended by the system. A framework that will capitalize on the strength of the employee enabled by technology shall be the onus of this paper. The sole purpose of which is to ensure the customer focused operation of the hotel while practicing processes that feed on continual improvements to manage the bottom line. Using these strategies, Lea dership in the industry and profitability should not be far behind. METHODOLOGY The valuable discussions in Operation Management have been the inspiration by this writer to seek out more knowledge in pursuit of excellence. Thus, it led to the discovery that the concepts presented herein have been in existence for some time, and various authors not only wrote extensively on the subjects but they have exhaustively been part of its continual improvement so to speak. Capitalizing from the experiences of these management gurus and the erudite deliberation in Operations Management this author therefore recommend a more comprehensive examination of the Hotel’s Customer Service. Using the ISO 9001:2008 Quality Management System framework, this author