The force of attraction between two unit point masses separated by a unit distance is called

$(i)$ How is the force of attraction dependent on the masses of objects and the distance between them?
$(ii)$ The mass of the Earth is $6 \times 10^{24} \, kg$ and that of a natural satellite is $6.5 \times 10^{20} \, kg$. If the distance between them is $3.35 \times 10^{6} \, km$, calculate the force exerted by the Earth on it. $(G = 6.7 \times 10^{-11} \, Nm^{2} kg^{-2})$

$A$ stone is dropped from the top of a tower. Its speed after it has fallen $20 \, m$ is (Take $g = 10 \, m s^{-2}$): (in $, m s^{-1}$)

The acceleration due to gravity on the surface of the Earth is:

Two objects of different masses falling freely near the surface of the moon would:

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.