Two objects have masses of 4 MG4MG and 48 MG48MG. How much does the gravitational potential energy between the objects change if the distance between them changes from 7 m7m to 2 m2m?

1 Answer
Jul 18, 2017

We will use the formula for the graviattional potential enegry
U=-G(Mm)/rU=GMmr

Explanation:

Let's start with the 7m7m

U_1=-G(Mm)/r=-(6.67*10^(-11)*4*48*10^6)/7=-0.002U1=GMmr=6.6710114481067=0.002Joules

and at 2m2m

U_2=-G(Mm)/r=-(6.67*10^(-11)*4*48*10^6)/2=-0.006U2=GMmr=6.6710114481062=0.006Joules

so the difference is ΔU=U_2-U_1=-0.004Joules

The potential energy decreases because the masses come closer.