What is the nature of motion of an object falling freely under the action of gravity?

What do you mean by free fall?

The weight of an object at the centre of the earth of radius $R$ is

What is meant by free fall? Two bodies,one of mass $1\,g$ and other of mass $1\,kg$,are dropped from the same height in a vacuum. Compare the two time intervals in which the two bodies will hit the ground.

Choose the correct alternative:
$(a)$ Acceleration due to gravity increases/decreases with increasing altitude.
$(b)$ Acceleration due to gravity increases/decreases with increasing depth.
$(c)$ Acceleration due to gravity is independent of the mass of the earth/mass of the body.

If a planet existed whose mass and radius were both half that of the Earth,the acceleration due to gravity at its surface would be: (in $, m s^{-2}$)