Page 116 - Viva ICSE Science 4 : E-book

ACTIVITY TIME
To understand the earth’s gravitational force

Aim:
To see what happens when a ball is just dropped down on the ground and when it is thrown
higher in the air

You Need:
Two balls
What to Do:

• Take one ball and just drop it on the ground.
• Now, take another ball and throw it in the air with force.
• See what happens in both the cases.

Observation:
You will observe that in both the cases, the balls will fall down on the ground. The fi rst ball will
take lesser time to fall onto the ground. The second ball will take some more time to fall as it
travels a longer distance in the air before it falls. Both the cases show that things always fall on
the ground.
Result:

This shows that the gravitational force of the earth pulls every object towards itself.

ACTIVITY TIME

Rough surface causes more friction than the smooth surface
Aim:
To see how rough and smooth surface aff ects frictional force
You Need:
A rough grass surface, a smooth surface like fl oor, a ball

What to Do:
• Take the ball and throw it by applying some force such that it rolls on the rough grass
surface. See how far the ball travels on the rough surface.
• Now, roll the ball on the smooth fl oor with the same force that you have applied on the
rough surface and see what happens.
Observation:

You will observe that the ball travels a longer distance on the smooth surface than the rough
surface, before it stops.

Result:
This shows that a rough surface causes more friction than the smooth surface.

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