Finding the velocities of two balls before they touch each other

[Eitan Levy]

Homework Statement

Two balls are given, the distance between their centers is 8R. Both have a radius of R.[/B]
One ball has a mass of 2m and the other has a mass of m.
The question is: What will be their velocities right before they touch each other
Answer: V_m=√(GM/R), V_2m=0.5√(GM/R)

Homework Equations

F=GMm/r²

The Attempt at a Solution

I tried this equation:

https://imgur.com/a/9QEWW , but I don't know how to continue.
Thanks a lot![/B]

 

[Chandra Prayaga]

Have you tried using conservation of energy and momentum?

 

[Eitan Levy]

Have you tried using conservation of energy and momentum?

Ohhhh, I thought those questions don't include them, so this is the only way to solve it?

 

[Chandra Prayaga]

That is certainly a very simple way.