On a frictionless, horizontal air table, puck A (with mass 0.250 kg) is moving toward puck B (with mass 0.350 kg), which is initially at rest. After the collision, puck A has a velocity of 0.120 m/s to the left, and puck B has a velocity of 0.650 m/s to the right. (a) What was the speed of puck A before the collision? (b) Calculate the change in the total kinetic energy of the system that occurs during the collision.

Solution 21E Problem (a) Step 1: Mass of puck A m = 0.21g Mass of puck B m = 0.35Kg 2 Velocity of puck B u = 0 2 After collision Velocity of puck A v = -0.12 m/s (moves in opposite direction) 1 Velocity of puck B v = 0.62m/s