The value of acceleration due to gravity

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.

How much momentum will a dumbbell of mass $10 \, kg$ transfer to the floor,if it falls from a height of $0.8 \, m$? Take acceleration due to gravity as $10 \, m s^{-2}$.

$A$ stone is allowed to fall from the top of a tower $100 \, m$ high and at the same time another stone is projected vertically upwards from the ground with a velocity of $25 \, m s^{-1}$. Calculate when and where the two stones will meet? (Take $g = 10 \, m s^{-2}$).

$A$ soft drink bottle is dropped by a waiter from the top of a hotel whose height is $100 \, m$. It takes $T$ seconds to reach the ground. Where will it be at $T/2$ seconds?

Prove that if a body is thrown vertically upward,the time of ascent is equal to the time of descent.