I am not looking so much for answers to problems, but I was sick the day of this lecture and need some clarification. I think I understand what to do, but some support would be great. 1. The problem statement, all variables and given/known data What is the gravitational force acting on a sphere on particle 'm' located at distance 'r' from center of sphere, assuming it is a uniform sphere of matter that has mass M, radius a, and a concentric cavity of radius a/3. Solve for r= a/6, r= 2a/3, r= 3a/2 I believe all I need is: F= G(m1m2/r^2) I have not attempted to solve, I would like to know it if this is the correct equation to use. Thanks.