What is the effect on the weight of a body due to the revolution of the earth?

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?

If the density of a planet is doubled without changing its radius,how does $g$ on the planet change?

$A$ man at the top of a tower throws an object horizontally,whereas he simply drops another. Will these two objects reach the earth at the same time?

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.

If the diameter of the earth becomes two times its present value and its mass remains unchanged,then how would the weight of an object on the surface of the earth be affected?