Page 99 - Viva ICSE Science 5 : E-book
P. 99
9 Work and Energy
We are familiar with the word work. Each one of KEY CONCEPTS
us does a lot of work every day. To do work we
need energy. Energy is the strength with which a • Work
• Energy
work is done. In this chapter, we will learn more
about the concepts of work and energy.
Work
Suppose you wish to move a wall by pushing it. You apply a lot of force on it, but it does
not move even a bit from its place. You feel tired and think you have done a lot of work
on the wall. But in terms of science, you have not done any work.
In science, work is said to be done only if force applied on a body moves it in the direction
of the force, thus changing its position.
Some examples of work done are as follows.
• Moving a cart
• Kicking a football
• Picking up a book from the table and keeping
it on the shelf
kicking football
• Swimming
• Hitting a ball with a bat
Work done
Some examples of work not done are as follows.
• Lifting a basket and putting it back on its position
• Pushing something that does not move, like a heavy
box or a wall reading
• Reading a book
• Singing
Work not done
85
