Universal Gravitation and spheres

[klopez]

Two spheres are released from rest when the distance between their centers is 12R. Sphere 1 has mass M and radii R while sphere 2 has mass 2M and radii 3R. How fast will each sphere be moving when they collide? Assume that the two spheres interact only with each other. (Use G for gravitational constant, and M and R as necessary.)

I need to find the symbolic answer for V1f and V2f, I have no clue, please help...due in an hour. Thanks

 

[Dick]

Use potential energy. Equate it to final kinetic energy. Use conservation of momentum to figure the ratio of V1f to V2f. You have 1hr, go. If you start showing some work, people will help you even more.