Page 88 - Science class 4

Ranjan is pushing Ram moorti is A man trying to move A crane lifting
the big box. pushing the wall. a rock off the road the same rock

Ranjan and Rammoorti are using force which is an activity. What do you think
will be the result? Ranjan may be able to move the box to a certain distance.
However, the wall will not move even though Rammoorti might apply greater

force.

According to Science, Ranjan is doing work, whereas Rammoorti is not doing
any work. Therefore, we can say work is done only if a force exerted on an
object moves it in the direction of the force.

Look at the pictures given below carefully. A man is trying to move the rock off

the road. Can he do it with out any help ? No, however a crane can do it easily.
Thus, work is done only when an object moves over a distance on applying

force. When work is difficult to do with our hands, we may use tools called
machines. Machines make our work easy. There are some simple machines
that we use in our everyday life. Let us learn about these machines.

Lever
Lever
Lever
A lever is an ordinary machine which is used to lift or move
heavy weights, cut things or open the lid of a tin. A pair of

scissors is an example of a lever. When we use a spoon
handle to open the lid of a tin, the spoon acts as a lever.

Pulley
Pulley
Pulley
A pulley is made from a wheel and a rope. It is used to lift things
easily. Villagers use pulleys to draw water from wells.

Wheel and AxleWheel and AxleWheel and Axle

Can you name some things that have wheels? Almost all
vehicles have wheels. The wheels have a rod connected to it.
This rod is called the axle. The axle moves the wheel. Moving

heavy objects becomes easy with the help of wheel and axle.