Question

Two objects have masses of `4 MG` and `48 MG`. How much does the gravitational potential energy between the objects change if the distance between them changes from `7 m` to `2 m`?

Answer 1

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

Explanation:

Let's start with the `7m`

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

and at `2m`

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

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

The potential energy decreases because the masses come closer.