Page 204 - Physics

Physics for Secondary Schools

Chapter Nine

Work, energy and power

Introduction

The terms ‘work’, ‘energy’ and ‘power’ are frequently used in everyday life.
A farmer ploughing the fi eld, a construction worker carrying bricks, a student
studying for a competitive examination, and an artist painting a beautiful
landscape, are all said to be doing work. In physics, the word ‘work’ covers a
defi nite and precise meaning, and so does energy and power. In this Chapter,
the concepts of work, energy and power will be discussed. The competencies
developed will enable you to perform various tasks in different contexts.

Think
the interrelation between work, energy and power in our daily life
practices
Concept of work

In everyday life, the term work means any activity in which effort (either mental or
physical) is exerted. However, in physics, work is done when a force acts on a body and
the body moves in the direction of the applied force. The work done is measured by the
product of the applied force and the distance moved by a body in the direction of the
applied force.

Suppose, a force F is applied to push a block resting on a table. If the block moves
through a distance d in the direction of the applied force, as shown in Figure 9.1, the
work is said to be done.
d

F

Figure 9.1: Illustration of work done
Then, Work done W ( ) = force F ( ) × distance d ( )

Therefore, W = Fd.

198
Student’s Book Form One

Physics Form 1 Final.indd 198 16/10/2024 20:58