Calculating Maximum Gravitational Force between Bowling Ball and Billiard Ball

[ladolce]

Homework Statement

A bowling ball (mass = 7.2 kg, radius = 0.10 m) and a billiard ball (mass = 0.41 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(m1xm2)/r^2

The Attempt at a Solution

i used the equation

F=[ 6.67x10^-11 ] [7.2] [.41]/1.2^2

but i keep getting a wrong answer of 1.2 x 10^-8 i don't know what i did wrong...

 

[ladolce]

I'm so confused, can anyone help me? :/

 

[Doc Al]

F=[ 6.67x10^-11 ] [7.2] [.41]/1.2^2

What's the distance between their centers?

 

[ladolce]

i think it's assuming that they're touching so it would be the sum of the radiuses..

 

[Doc Al]

Right. And what would that sum be?

 

[ladolce]

haha, oops so it's 0.128... i thought i did that, mustve typed it wrong...but still, taht wouldn't make my way right would it?

 

[Doc Al]

Looks like you did use the correct value for the distance between the centers. I see nothing wrong with your solution.

 

[ladolce]

i guess it's the way i entered it into webassign :(