Force between two objects

Question

The force of gravity between two small masses A and B when placed very near each other is 3.24x10^-7 N. What will the force between these objects be if both of their masses are doubled and the distance between them is tripled?

Answer 1

Hi Gnarls,

 

The force of gravity between two objects equals Gm₁m₂/r², where G is the universal gravitation constant, m1 and m2 are the masses, and r is the distance between them.  If the masses are doubled and the distance between them is tripled, then the new force of gravity between the masses is G(2m₁)(2m₂)/(3r)².

 

This equals 4Gm₁m₂/9r².   So the new force is 4/9 the strength of the original force.

 

So 4/9 * 3.24(10^-7) = 1.44 (10^-7) N

 

Hope this helps!