Page 73 - full

Friction is a force that holds back the movement of a sliding object. You will find
friction everywhere that objects come into contact with each other. The force acts in
the opposite direction to the way an object wants to slide. If a car needs to stop at a
stop sign, it slows because of the friction between the brakes and the wheels. If you
run down the sidewalk and stop quickly, you can stop because of the friction between
your shoes and the cement. It is friction which makes us able to walk on the floor and
to hold something with our hands. If there were no friction, we cannot hold an object.

Ball moving on the ground Grip of shoes Grip of tyre

What is Work? A boy pushing a box

In physics, work is said to be done when a force is
applied on a body to make it move through a distance.
For example, if you push a box and move it for some
distance, then here work is done by you. There are
other good examples of work that can be observed in
everyday life - a horse pulling a plow through the field, a
weightlifter lifting a barbell above his head etc. In each
case described here there is a force exerted upon an
object to cause that object to be displaced.

Simple Machine

A machine is a device which makes the work easier
and reduces our effort. Some of the simple machines
that we use in our daily life are as follows:
Lever
Inclined plane
Wheel and axle
Screw
Wedges
Pulley

77 77