Question

Two objects have masses of `9 MG` and `5 MG`. How much does the gravitational potential energy between the objects change if the distance between them changes from `500 m` to `20 m`?

Answer 1

`7.488xx10^-6N`

Explanation:

The equation for gravitational potential energy (G.P.E) between two bodies is

`U = G(m_1m_2)/r^2`

where `U` is G.P.E, `m` is the mass, and `r` is the distance. `G` is known as the gravitational constant and is approximately `6.67xx10^-11`.

Putting in values that we know, the initial G.P.E is

`U = 6.67xx10^-11 xx (9xx10^3xx5xx10^3)/500^2 = 1.2xx10^-8N`

and the final G.P.E is

`U = 6.67xx10^-11 xx (9xx10^3xx5xx10^3)/20^2 = 7.5xx10^-6N`

so the total change in G.P.E is

`7.5xx10^-6 - 1.2xx10^-8 = 7.488xx10^-6N`