# Introduction

## Work, Power and Energy

We have already discussed the concept of motion and force. When a force acts on a body and it moves through a certain distance, work is said to be done.The concept of work is closely related to energy as more the energy spent, more is the work done. A person with more power can also do more work. Let us study these concepts.

The terms 'work', 'energy' and 'power' are frequently used in everyday language. A farmer clearing weeds in his field is said to be working hard . In physics, the word work has a special meaning. Work is said to be done when the force acting on body produced motion in it in the direction of force (or in the direction of component of force). Thus a boy pushing the wall is doing no work from physics’ point of view. A body which has the capacity to do work is said to posses energy. The greater the capacity of a body to do work, the greater the energy it has.The term power is usually associated with speed. In karate, a powerful punch is one delivered at great speed. In physics we shall define these terms very precisely. Thus work, energy and the power are related to each other.Now we will understand each of these one by one.To score More in your class 9 refer NCERT solutions for class 9