posted by Sam .
A solid uniform sphere has a mass of 7.0 104 kg and a radius of 1.2 m.
(a) What is the magnitude of the gravitational force due to the sphere on a particle of mass m = 0.7 kg located at a distance of 2.1 m from the center of the sphere?
(b) What if it is 1.0 m from the center of the sphere?
I will gladly help the first student who shows evidence of his or her own work. You do not appear to be among that vanishing group.
Okay so far i have F=Gm1m2/r^2
what do i use for r?