A hockey puck of mass m traveling along the x axis at 4.5 m/s hits another identical hockey puck at rest.If after the collision the second puck travels at a speed of 3.5 m/s at an angle of 30° above the x axis, is this an elastic collision?
A)Yes, since momentum is conserved.
B)No, since momentum is not conserved.
C)Yes, since kinetic energy is conserved.
D)No, since kinetic energy is not conserved.
E)Not enough information.

Question

Quizplus · Accepted Answer

The collision is not elastic because kinetic energy is not conserved. This can be seen by calculating the kinetic energy before and after the collision. Before the collision, the first puck has kinetic energy of (1/2)mv^2 while the second puck has no kinetic energy. After the collision, the first puck transfers some kinetic energy to the second puck, causing it to move, and the two pucks move at an angle. Therefore, the total kinetic energy after the collision is not equal to the total kinetic energy before the collision, meaning kinetic energy is not conserved.

A Hockey Puck of Mass M Traveling Along the X