Question

Question #cc2cc

Answer 1

Inside the sphere gravity increases linearly from zero at the centre to, in this case, ag at the surface, so:

`r_1 = (2.8)/4`km

At and away from the surface it is the more familiar relationship, following the more familiar form of Newton's Law of Gravity:

`g = (GM)/r^2`

As `GM` is constant, solve this:

`ag (2.8)^2 = (ag)/4 r_2^2 qquad (= GM)`