Page 6 - Force 10

Unit 1: Gravitational force cont…… 2

Thus acceleration acted on a falling object is
Falling of parachute Falling of parachute on equal to ‘g’ (acceleration due to gravity).
on earth moon
Due to continuous air It is free-fall due to the Case 2: If we throw a ball upward in the air, a
resistance offered by absence of air gravitational force acts downwards on it. As force
the atmospheric air, it resistance. acts downwards, acceleration is in downwards
is not free-fall.
The acceleration The acceleration direction. It means velocity will decrease with
time and at one point, it becomes zero.
produced in falling produced in the falling
parachute is less than parachute is equal to Due to the gravitational force, the ball takes U-
the acceleration due to the acceleration due to turn and reaches to ground with same speed with
gravity. gravity. which it was thrown up. As object is moving
Safe landing is Serious accident will downwards and acceleration is also in downward
possible due to the occurs due to the high direction, velocity increases.
very less final final velocity.
velocity.

Velocity and Acceleration

➥ When an object moves with constant velocity,
such motion is called uniform motion.
➥ When an object moves with increasing
velocity, motion is called accelerated motion.
➥ When an object moves with decreasing
velocity, motion is called retarded motion.
➥ Direction of velocity is the direction in which
body is moving.

Falling Bodies
Case 1: When an
object is released The value of ‘g’ is taken as positive in the case of
from top, it falls down object moving towards earth and taken as
due to gravitational negative in the case of object is thrown in
force of earth. As opposite direction of earth.
force acts
downwards,

acceleration ‘a’
would be in downward direction.
As object is moving downwards and acceleration
is also in downward direction, velocity increases.
So when an object is released from top, it
does accelerated motion (increasing velocity).

Do you know?
Henry Cavendish determined the value of G experimentally for the first time by using a sensitive ( torsion)
balance.