HCI 05 WEP Lecture Notes

Hwa Chong Institution (College) H2 Physics C1 2023 1 Chapter 5 Work, Energy and Power Pictures (from top left and bottom left to right): credits to www.knxradio.com/guardian.co.uk/fluidmechanic.co.uk/aafaq.genistra.com “There is a fact, or if you wish, a law governing all natural phenomena that are known to date. There is no known exception to this law – it is exact so far as we know. The law is called the conservation of energy. It states that there is a certain q uantity, which we call “energy” that does not change in the manifold ch anges that nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says there is a numerical quantity which does not change when something happens. It is not a description of a mechanism, or anything concrete; it is a strange fact that when we calculate some number and when we finish watching nature go through her tricks and calculate the number again, it is the same. It is important to realize that in physics today, we have no knowledge of what energy “is.” We do not have a picture that energy comes in little blobs of a definite amount. It is not that way. It is an abstract thing in that it does not tell us the mechanism or the reason for the various formulas.” Richard Feynman The Feynman Lectures on Physics (Volume 1) A B C D

Hwa Chong Institution (College) H2 Physics C1 2023 2 Contents H2 Physics Syllabus 9749 ................................ ................................ ................................ ................................ ....... 3 5.1 Work ................................ ................................ ................................ ................................ ............................ 4 5.1.1 Work done by a constant force ................................ ................................ ................................ ................. 4 5.1.2 Work done by a variable force ................................ ................................ ................................ .................. 6 5.2 Energy ................................ ................................ ................................ ................................ ......................... 7 5.2.1 Kinetic energy, Ek................................ ................................ ................................ ................................ ..... 7 5.3 Potential energy ................................ ................................ ................................ ................................ ........... 9 5.3.1 Gravitational Potential Energy (GPE), Ep or U ................................ ................................ ........................ 10 5.3.2 Relationship between Gravitational Force and Gravitational Potential Energy ................................ ......... 12 5.3.3 Elastic Potential Energy ............................