# Gravity and mass of two objects

1. Jun 4, 2008

### AnkhUNC

1. The problem statement, all variables and given/known data
There are two masses of unknown weight on a straight line with a small red particle between them. At x (Measured from the center of m1) = .515 the particle does not move. What is the ratio of the two masses? i.e. m2/m1.

2. Relevant equations

3. The attempt at a solution

So do I use F = G*m1*m2/r^2? Since the particle isn't moving then the forces are balanced does this mean F = 0 then?

2. Jun 4, 2008

### tiny-tim

Hi AnkhUNC!
Not exactly … you use F1 = G*m*m1/r1^2 and F2 = G*m*m2/r2^2 and F1 = F2.

Hint: what is the relationship between m1/m2 and r1/r2?

3. Jun 4, 2008

### AnkhUNC

On the right side the min x = .043 on the left side the max is .957. It starts out at .5 though which is in the middle so I guess <- is 0 and -> is 1.

r1/r2 = 1, they're both .5 away so .5/.5 = 1.

m2 is greater than m1 because the attraction is stronger so does m2 = .515 and m1 = .485?

4. Jun 4, 2008

### AnkhUNC

So F = G*m*m1*m2?

5. Jun 5, 2008

### tiny-tim

Sorry, AnkhUNC, but I honestly have no idea what this means.
Hint: divide F1 by F2.