Question

The centers of a 15 kg lead ball and a 140 g lead ball are separated by 8.0 cm.

What gravitational force does each exert on the other? Answer: 2.2×10^−8 N

Now: What is the ratio of this gravitational force to the weight of the 140 g ball?

I don't know how to do this, I've tried it a hundred different ways and cant seem to get it. Help?

Answer 1

Divide your answer to the first part by m*g, where m = 0.14 kg and g = 9.81 m/s^2

Weight = 1.373 N

2.2*10^-8/1.373 = ?

Answer 2

Fnet = (mMG)/r^2
G= 6.67x10^-11 N.m^2/kg^2
r=8.0cm = 0.08m
M=140g = 0.140kg
m=15kg
F = (15kg x 0.140kg x 6.67x10^-11 N.m^2/kg^2)/ (0.08m)^2
F = 2.19x10^-8 N