Give an example of the motion of an object under the influence of gravitational force on Earth.

$A$ stone is dropped from a height of $20\, m$.
$(a)$ How long will it take to reach the ground?
$(b)$ What will be its speed when it hits the ground? $(g=10\, m s^{-2})$

$(a)$ Prove that if the Earth attracts two bodies placed at the same distance from the center of the Earth with equal force,then their masses will be the same.
$(b)$ Mathematically express the acceleration due to gravity experienced by a free-falling object.
$(c)$ Why is $G$ called a universal gravitational constant?

Two stones $A$ and $B$ are dropped from a multi-storey building. Stone $A$ is dropped from $100 \, m$ and at the same time stone $B$ is dropped from $50 \, m$ height. Both of them reach the earth at the same time. Will they have equal velocity while reaching the ground? Calculate and find out the answer (Take $g = 10 \, m s^{-2}$).

Why is the value of $g$ greater at the poles than at the equator?

An object weighs $10 \, N$ in air. When immersed fully in water,it weighs only $8 \, N$. The weight of the liquid displaced by the object will be (in $, N$)