Elastic collision between 5.0 kg and 2.0 kg balls on a track

[tica86]

A 2.0 kg ball at rest is struck head-on by a 5.0 kg ball moving along a track at 10.0 m/s in an elastic collision. What is the speed of the 5.0 kg ball and the 2.0 kg ball after the elastic collision?

----I'm sure this is a pretty simple question but I don't where to start.
Is the following equation correct?

v1= 2m1/m1+m2 ?

please help

 

[fzero]

v1= 2m1/m1+m2 ?

What are the units of speed? Does the RHS of this equation have those units?

You will need to use conservation of energy and momentum to solve this. Compute the momentum and energy of the system before and after the collision, using symbols to represent the unknown velocities. You will have 2 equations to solve for the 2 unknown speeds.