Two electrons, one at rest and another with speed of vi = 0.970c moving in the positive x direction collide. After the collision, one electron is observed to move with a speed of v1f = 0.965c at an angle θ1 = 15.2° with the x axis.

1 Use conservation of momentum to find the velocity of the second electron. 

2 Based only on the original data given in the problem, use conservation of kinetic energy to find the speed of the second electron.