ASRJC Physics Work, Energy and Power Notes

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 5-1 Additional Notes Topic 5: Work, Energy and Power Content: A. Work B. Kinetic Energy and Potential Energy C. Conservation of Energy D. Power and Efficiency Learning Outcomes: Candidates should be able to: (a) define and use work done by a force as the product of the force and displacement in the direction of the force. (b) calculate the work done in a number of situations, including the work done by a gas which is expanding against a constant external pressure: W = pV. (To be discussed in First Law of Thermodynamics) (c) give examples of energy in different forms, its conversion and conservation, and apply the principle of energy conservation to simple examples. (d) show an appreciation for the implications of energy losses in practical devices and use the concept of efficiency to solve problems. (e) derive, from equations for uniformly accelerated motion in a straight line, the equation Ek = 1 2 mv2 (f) recall and use the equation Ek = 1 2 mv2. (g) distinguish between gravitational potential energy, electric potential energy and elastic potential energy. (h) deduce that the elastic potential energy in a deformed material is related to the area under the force-extension graph (i) show an understanding of, and use the relationship between force and potential energy in a uniform field to solve problems. (To be discussed in Gravitational Field) (j) derive, from the definition of work done by a force , the equation Ep = mgh for gravitational potential energy changes near the Earth’s surface. (k) recall and use the formula Ep = mgh for gravitational potential energy changes near the Earth’s surface. (l) define power as work done per unit time and derive power as the product of force and velocity in the direction of the force Name: _______________________________ ( ) Class: 25 / ____

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 5-2 Additional Notes Relating Science and Society There is heavy reliance on fossil fuels (e.g. crude oil, natural gas and petroleum products) for electricity generation in Singapore. It is important to capitalise on innovative ideas and technologies to promote the efficient use of energy, especially in the major sectors of energy use, namely power generation, industry, transport, buildings and households. It is also important to grow clean energy capabilities such as solar energy to reduce the dependence on fossil fuels. • Energy is the ability to do work; whereas work is the transfer of energy, or the process of converting energy. • When work is done, energy is transferred. A.1 Work Done by a Force • If a body moves as a result of a force being applied to it, the force is said to be doing work on the body. • When you exert a force F on an object making it move a displacement s in the direction of the force, your work done on the object