Question

A hockey puck with mass 0.237 kg traveling along the blue line (a blue-colored straight line on the ice in a hockey rink) at 1.4 m/s strikes a stationary puck with the same mass. The first puck exits the collision in a direction that is 30° away from the blue line at a speed of 0.79 m/s (see the figure).
What is the direction and magnitude of the velocity of the second puck after the collision?

Answer 1

Assume that total momentum is conserved, and solve for the speed and direction of the second puck.

Answer 2

θ = 30°
x-direction:
vi + vf cos θ = x
1.4m/s - 0.79m/s(√3/2) = 0.716m/s

y-direction:
vf sin θ = y
0.79m/s * 0.5 = 0.395m/s

Speed =
√(x² + y²)
√[(0.716)² + (0.395²)] = 0.818 m/s

Direction:
Tan-¹ (y/x) = Tan-¹ (.395/.716) = 28.88° -> 28.9°