RI 2022 Work, Energy and Power

Chapter 5 RAFFLES INSTITUTION YEAR 5-8 PHYSICS DEPARTMENT WORK, ENERGY AND POWER Content • Work • Energy conversion and conservation • Potential energy and kinetic energy • Power Learning Outcomes . Candidates should be able to: (a) (b) (c) (d) (e) (f) define and use work done by a force as the product of the force and displacement in the direction of the force. 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 1. give examples of energy in different forms, its conversion and conservation, and apply the principle of energy conservation. show an appreciation for the implications of energy losses in practical devices and use the concept of efficiency to solve problems. derive, from the equations for uniformly accelerated motion in a straight line, the equation EK= ~mv2. 2 1 recall and use the formula EK = -mv2. 2 (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 rela~ionship between force and potential energy in a uniform field to solve problems. 0) derive, from the definition of work done by a force, the formula EP = mgh for gravitational potential energy changes near the Earth's surface. (k) recall and use the formula Ep = mgh for potential energy changes near the Earth's surface. (I) define power as work done per unit time and derive power as the product of a force and velocity in the direction of the force. 1 Italicized part, i.e. work done by an expanding gas is not in the H1 syllabus. 1

5.1 5.1.1 Work done by a Constant Force on a System Definition Note Definition Introduction RAFFLES INSTITUTION YEAR 5-6 PHYSICS DEPARTMENT Energy is one of the most fundamental concepts in science, and is discussed in the context of Newtonian mechanics. Energy is present in various forms, w~h endless conversion from one form to another. The conservation of energy is an essential principle in Physics. The concept of work links energy and force, as work is a means of energy conversion through the application of a force. In certain situations, the concepts of work and energy can be applied to solve the dynamics of a mechanical system without directly resorting to Newton's laws. Beyond mechanics, this problem-solving approach focusing on energy can be applied to a wide range of phenomena in electromagnetism, and thermal and nuclear physics. The work-energy approach often provides a much simpler analysis than that obtained from the direct application of Newton's laws, since the former deals with scalar rather than vector quantities. In this section, we will discuss the concept of work. Work Done b a Constant Force on a S stem In scientific terms, work is done by a force on an object when the object