Page 119 - Viva ICSE Science 5 : E-book

11 Simple Machines

We all do work in our every day life. In order to KEY CONCEPTS
do a work faster we use a machine. A machine
• Need for machines
is a device or a tool which helps us to do a work
• Types of simple machines
easily by reducing the time and the amount of

force.

Machines are of two types—simple (like lever and pulley) and complex (like scooter
and washing machine). In this chapter, we will learn about simple machines and their
use.

Need for Machines

We know that a work is said to be done when the force acting on an object displaces it.
A machine acts by reducing the force needed to displace an object. In simple words, it

makes our work easy. It also reduces the time required to do the work. For example, we
use a can opener to open a can of cold drink and a trolley to carry load in a departmental
store. In these examples, can opener and trolley are simple machines.

Types of Simple Machines

There is a wide range of simple machines. Let us discuss the most common simple
machines like lever, inclined plane, pulley, wheel and axle, screw and wedge.

Lever

Lever is a rigid bar or rod that rests on a support called fulcrum. It is a simple machine

used to lift heavy weights with minimum amount of eff ort.

For example, to move a big stone with hands or with the help of a stick, a person needs
to apply a lot of force. But if a small stone is kept as a support below the rod (see fi gure)
and force is applied from the other end, the stone moves with less eff ort.

In the given example, the big stone is called load, the force applied is referred to as eff ort

and the small stone which provides support is known as fulcrum.

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