Page 7 - Force 10

Unit 1: Gravitational force cont……
Guinea and feather experiment
The acceleration produced on a freely falling body
is independent of its mass. Earlier it was thought
that the lighter objects falls slowly and the
heavier objects falls more rapidly, when dropped
simultaneously from the same height.
In 1590 A.D. Galileo Galilei, a great scientist
performed experiments in the leaning tower of
Pisa (Italy), in the presence of large number of
people. He demonstrated that the acceleration of
an object falling freely towards the earth
doesn’t depend on the mass of the
object.However, When a piece of paper and
stone were dropped simultaneously, the stone
reached the ground earlier due to air resistance.
To verify this fact, Robert Boyle performed
an experiment in a vaccum, a coin and feather are
kept inside a tall glass tube with closed ends.
Do you know?
A person who can jump 1 m on the earth can jump about 6 m on the moon. Since the value of
acceleration due to gravity of the moon is almost 6 times less than that of the earth.
2
Conclusion: The acceleration produced on the
freely falling bodies is same for all bodies and
independent to the mass of the falling bodies.
Memory tips
 The four fundamental forces of nature are
the frictional force, gravitational force,
electromagnetic force and nuclear force.
The gravitational force of attraction is the
weakest force among these.
 According to Geo-centric theory, the solar
system revolves around the earth.
 According to Helio-centric theory, the solar
system revolves around the sun.
 Nicholas Copernicus proposed the helio-
th
centric theory in 16 century.
 The value of acceleration due to gravity is
maximum at the earth surface and
decreased with height and depth. It
becomes zero at the center of the earth.
 Acceleration produced on a freely falling
body is equal to the acceleration due to
gravity. For example, the acceleration of a
freely falling body on the moon is 1.67
2
m/s .
 Weight of an object decreases inside a
mine since the effective mass of the earth
gradually decreases on climbing down in a
mine.
 Jupiter is the biggest planet which has 319
times larger mass and 11 times greater
radius than that of the earth but the gravity
is only 2.5 times more than that of the
earth.