Question

A blue puck with a mass of 3.90×10−2 , sliding with a speed of 0.170 on a frictionless, horizontal air table, makes a perfectly elastic, head-on collision with a red puck with mass , initially at rest. After the collision, the velocity of the blue puck is 5.0×10−2 in the same direction as its initial velocity.
Find the magnitude of the velocity of the red puck after the collision?

Answer 1

You will have to use conservation of energy, and momentum, having two equations and two unknowns. The algebra is somewhat messy, but at least it is restriced to the x direction.