What will happen to the force if we
decrease r by a factor of 2 ?

The new force will become 1/4 times of the initial force.

Explanation:

The Coulomb force between two charges is directly proportional to the product of charges and inversely proportional to the square of the distance between them.

It can be given by :

....(1)

r is distance

If we decrease the r by a factor of 2, r'=2r.

New force will become,

So, the new force will become 1/4 times of the initial force.

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.