# The Gravitational Force (between two spherical objects)

princess7115
A bowling ball (mass=7.2 kg, radius=0.11m_ and a billiard ball (mass=.38kg, radius= .082m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the other?

I figured I was supposed to use F=Gm1m2/r^2 but I didn't know how to use the equation because the problem gave me to radii.

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Leong
if we want the maximum force, what can you say about the distance between them?

princess7115
i'm not sure, I really don't get it. I just know that I'm supposed to use r and in every other problem, they give it to me and I don't know why I have two distances.

Leong
ok, what is r?

princess7115
I got it. I just added the radii together. Because I figured if it didn't tell me how far apart the spheres were, I had to assume they were next to each other.

Leong
that is the way but it is not because the question didn't give you the distance.
maximum force means the distance is the least, this happens when they are next to each other, and that is why you add the radii together to get the r.

princess7115
awesome, thank you for your help