Is it possible to shield a body from a gravitational field?

State whether the following statement is True or False:
All objects attract each other along the line joining their centre of mass.

Calculate the force of gravitation between two objects of masses $10 \; kg$ and $20 \; kg$ at a distance of $10 \; m$ from each other. $\left[G = 6.67 \times 10^{-11} \; Nm^2 kg^{-2}\right]$

$A$ 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 $25\, m/s$. Calculate when and where the two stones will meet.

State the universal law of gravitation. Write the $SI$ unit of $G$. The gravitational force between two objects is $100 \, N$. How should the distance between the objects be changed so that the force between them becomes $50 \, N$?

State any two properties of gravitational force.