Gravitational Force of Bowling & Billiard Balls - Homework

[RKNY]

Homework Statement

A bowling ball (mass = 7.2 kg, radius = 0.13 m) and a billiard ball (mass = 0.40 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the other?

Homework Equations

F = G(m1m2/r^2)

The Attempt at a Solution

Im confused about the radius portion of the problem. Shouldn't you add up the radius of both (0.028 + 0.13) and use that answer in the equation?

 

[denverdoc]

I would think that's as close as the two could come together and therefore the greatest force would be generated. You seem to imply that this is not the case?

 

[RKNY]

I would think that's as close as the two could come together and therefore the greatest force would be generated. You seem to imply that this is not the case?

F = G x m1 x m2 / r^2

F = (6.67 x 10^-11) x (7.2) x (0.40) / (0.148) x 2

F = .000000001

Doesn't seem to be right when I go and check it.

 

[denverdoc]

you have .44 above when the problem states .4, and .148 instead of .158 as you suggested using in the denom. maybe follow suit and go to bed as I intend to now.

 

[RKNY]

you have .44 above when the problem states .4, and .148 instead of .158 as you suggested using in the denom. maybe follow suit and go to bed as I intend to now.

sorry, I went back and changed everything. Now everything seems to be the way I attempted it.

 

[denverdoc]

well the denominator still shows 0.148, when its 0.158; also make sure to use exponential entry with your calculator; if it doesn't support such, then use the windows free calculator--use the more advanced of the two available. I get something like 7.7e-9