Universal Gravitation and spheres

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To find the final velocities of two spheres before collision, apply the conservation of energy principle by equating gravitational potential energy to kinetic energy. The initial potential energy can be calculated using the formula U = -G(m1*m2)/r, where r is the distance between the centers of the spheres. Use conservation of momentum to establish the relationship between the final velocities, leading to the equations V1f and V2f. The ratio of the final velocities can be derived from their masses and the conservation principles. This approach will yield the symbolic answers for V1f and V2f needed for the problem.
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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
 
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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.
 

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