$A$ ball is thrown vertically upward,acceleration due to gravity is:

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 $, m s^{-2}$)

Identical packets are dropped from two aeroplanes,one above the equator and the other above the north pole,both at height $h$. Assuming all conditions are identical,will those packets take the same time to reach the surface of the Earth? Justify your answer.

$A$ 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 $g = 10 \, m s^{-2}$).

$(a)$ What do you mean by acceleration due to gravity?
$(b)$ What is the value of $g$ on the surface of the earth?
$(c)$ On what factors does the value of $g$ depend?

At the top of its path,a projectile: