NCERT Book Class 8 Science Chapter 8 Force and Pressure

FORCE AND PRESSURE

I
n Class VII, you have learnt how by a batsman? (Fig. 8.1). In all these
objects move. Do you recall how we situations the ball is either made to
can decide whether an object is move faster or slower or its direction
moving faster than the other? What does of motion is changed.
the distance moved by an object in unit We often say that a force has been
time indicate? You also know that a applied on a ball when it is kicked,
moving object like a ball rolling on the pushed, thrown or flicked. What is a
ground slows down. Sometimes it may force? What can it do to bodies on which
change its direction of motion. It is also it is applied? We shall seek answers to
possible that the ball may slow down such questions in this chapter.
and also change its direction. Have you
ever wondered what makes an object 8.1 Force – A Push or a Pull
slow down or go faster, or change its
direction of motion? Actions like picking, opening,
Let us recall some of our everyday shutting, kicking, hitting, lifting,
experiences. What do you do to make flicking, pushing, pulling are often
a football move? What do you do to used to describe certain tasks. Each
make a moving ball move faster? How of these actions usually results in
does a goalkeeper stop a ball? A some kind of change in the state of
hockey player changes the direction motion of an object. Can these terms
of the moving ball with a flick of the be replaced with one or more terms?
stick. How do fielders stop a ball hit Let us find out.

(a) (b) (c)
Fig. 8.1 : (a) A goal keeper saving a goal, (b) A hockey player flicking a ball, and
(c) A fielder stopping a ball