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

$A$ ball is thrown vertically upwards with a velocity $u$. Calculate the velocity with which it falls to the earth again.

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?

What is the source of centripetal force that a planet requires to revolve around the Sun? On what factors does that force depend?

Earth is continuously pulling the moon towards its centre,still it does not fall to the earth,why?

How does the force of attraction between two bodies depend upon their masses and the distance between them? $A$ student thought that two bricks tied together would fall faster than a single one under the action of gravity. Do you agree with his hypothesis or not? Comment.