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What is free fall
When a body or object
falls towards earth
due to gravitational force of earth
and without any other force acting on it
It is called free fall
When a body falls from sky to earth, does it fall with uniform speed?
No
It does not fall with uniform speed
Its speed actually increases as it falls on earth
This is due to acceleration due to gravity
What is the meaning of Acceleration due to Gravity?
When a body falls on earth
a uniform acceleration is produced (velocity or speed increases)
due to gravitational force of the earth
This is called acceleration due to gravity
This Acceleration is denoted by g
g = 9.8 m/s 2
Similarly,if a body is thrown upwards
a uniform retardation is produced (velocity or speed decreases)
This is denoted by
g = -9.8 m/s 2
How to Calculate Acceleration due to Gravity
We know that
Acceleration does not depend upon Mass of Body
If 2 objects are falling, even if they have different mass, still they will fall with same acceleration of 9.8m/s 2
Explanation
We now know that
g = G x M/r 2
here
G = Gravitational Constant
M = Mass of earth
r = Radius of earth
All these are constant and do not change
So we can say that
Value of g remains constant
It does not depend upon mass of body falling
If 2 objects are falling, even if they have different mass, still they will have same acceleration
Why does stone fall on earth quickly but a paper takes time to fall?
It is because paper faces more air resistance compared to stone
Paper has lesser mass compared to its Surface area so it faces more air resistance and hence fall slowly
Stone has more mass compared to its surface area so it faces lesser air resistance while falling down and hence fall quickly
Note
Acceleration due to gravity does not depend upon mass of object
If we remove air and then make both paper and stone fall, both will fall with same acceleration of 9.8 m /s 2
it is because of air resistance that stone falls faster but paper takes time to fall
Acceleration due to gravity is different at poles and at equator
Questions
Q 1 Page 136 - What do you mean by free fall?
Q 2 Page 136 - What do you mean by acceleration due to gravity
NCERT Question 8 - What is the acceleration of free fall?
NCERT Question 9 - What do we call the gravitational force between the earth and an object?
NCERT Question 10 - Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? [Hint: The value of g is greater at the poles than at the equator.]
NCERT Question 11 - Why will a sheet of paper fall slower than one that is crumpled into a ball?
