1. The problem statement, all variables and given/known data A ball of mass M travelling at non-relativistic speed v elastically collides with a stationary ball of mass m. (a)Show that the maximum speed which the second ball can have is: 2Mv/(M+m) (b)What is the minimum speed? 3. The attempt at a solution (a) Method 1 Go into ZMF frame: step 1: find VCM step 2: u2' = u2 - VCM step 2: pi = pf = 0 step 3: v2' = -u2 step 4: go back into lab frame by adding VCM Method 2 1)Speed of approach = speed of separation 2)conservation of momentum 3)done. But the puzzling thing is that why is this the maximum speed? Isn't this the actual acquired speed? (b) Do we assume a head-on collision? If it is a head-on collision won't the speed be the same as part (a)? assuming a non head-on collision by including angles and stuff doesn't help..