In a one-dimensional elastic collision between two identical pucks, where one is moving at 3 m/s to the right and the other initially at rest, what are their final velocities after the collision?

• A. First puck moves right at 3 m/s; second remains at 0 m/s.
• B. First puck moves left at 3 m/s; second moves right at 3 m/s.
• C. First puck stops; second moves right at 3 m/s.
• D. First puck stops; second moves right at 0 m/s.

Answer: (D)

In a one-dimensional elastic collision between two identical masses, they effectively exchange their velocities. Since the moving puck starts at 3 m/s to the right and the other is at rest, after the collision the moving puck transfers its velocity to the stationary one, while it itself comes to a stop. This also keeps momentum and kinetic energy the same as they were before the collision, which matches the numbers here.

So, the first puck ends up at rest, and the second puck moves to the right at 3 m/s.