Mona weighs $750 \, N$ on Earth:
$(i)$ On the planet Mars,the force of gravity is $38 \%$ of that of Earth. How much will Mona weigh on Mars?
$(ii)$ What will be Mona's mass on Earth (take $g = 10 \, m s^{-2}$)?

Three students $A, B$ and $C$ were performing an experiment to establish the relation between the weight of a wooden block and the minimum force required to just move it on a horizontal surface. The experimental setup used by each is as shown in the figures given below.
The result obtained by them will be:

The acceleration due to gravity at the moon's surface is $1.67 \, m s^{-2}$. If the radius of the moon is $1.74 \times 10^{6} \, m$,calculate the mass of the moon. (Use $G = 6.67 \times 10^{-11} \, N m^{2} kg^{-2}$)

What is the ratio of the gravitational force between two masses kept at a certain distance in air to the force between them when kept in any other medium?

Two objects of masses $m_1$ and $m_2$ having the same size are dropped simultaneously from heights $h_1$ and $h_2$ respectively. Find out the ratio of time they would take in reaching the ground. Will this ratio remain the same if $(i)$ one of the objects is hollow and the other one is solid and $(ii)$ both of them are hollow,size remaining the same in each case. Give reason.

What is the gravitational force between the earth and a body called?