Page 35 - Science Class 6 Times Publication

1. Lever

A lever is a long rigid bar that is capable of rotating about a  xed

point. The xed point about which a lever rotates is called fulcrum. A
lever consists of three main parts - load, effort and fulcrum. The load
is the object that has to be lifted by the lever whereas the effort is the
force applied to the lever to lift the load.

effort distance

load
distance Fulcrum

The advantage of the lever depends upon the load distance and effort
distance. In a lever, the distance between the fulcrum and the load
is called load distance (Ld) or load arm (La) whereas the distance
between the fulcrum and the effort is called effort distance (Ed) or
effort arm (Ea).

The lever can be classied into three types on the basis of position of

load, effort and fulcrum. They are:

a. First class lever
The lever in which the fulcrum lies at any point in the middle of load

and effort is called rst class lever. Crowbar, scissors, see-saw, beam
balance, dhiki, cutting shears, etc are some examples of  rst class
lever. F

E L E
F L

Crowbar Scissors Beam balance

E L

F F
L E E F L

See-saw Metal cutting shears Dhiki

Times' Crucial Science and Environment 31 Book 6