Gravitational force for a ball and particle

[PKay]

Homework Statement

How far from a very small 110kg ball would a particle have to be placed so that the ball pulled on the particle just as hard as the Earth does?

Homework Equations

Fg= gMm/r^2

The Attempt at a Solution

I used the equation and plugged in the numbers for the ball and the earth, but then I realized that I needed to use the mass for the particle. However, I don't know what the mass for the particle is.

 

[PhysicoRaj]

It does not require the mass of the particle.

 

[PKay]

Am I supposed to leave it as a variable?

 

[PhysicoRaj]

It's your choice..if you do that, you can see it cancels out ultimately.

 

[PKay]

Thanks! I see it now... I end up getting R= R^2 * Mball/Mearth I'm hoping I'm in the right direction.

 

[PhysicoRaj]

Yes.

 

[PKay]

I get 7.49-10^-10 but it says I'm wrong.

 

[PKay]

Whoops. I'm sorry. I forgot to square root that. Thanks so much for your help! Now to tackle the other 2 monstrous problems.