A ball of mass 2 kg strikes a smooth fixed vertical wall with speed 10 m/s. Its velocity makes an angle 60° with the normal to the wall. The collision is perfectly elastic. If the magnitude of the impulse delivered by the wall is N N·s, find N.
Physics · Center of maas , Momentum and Collision · impuse and question based on it
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Question

A ball of mass 2 kg strikes a smooth fixed vertical wall with speed 10 m/s. Its velocity makes an angle 60° with the normal to the wall. The collision is perfectly elastic. If the magnitude of the impulse delivered by the wall is N N·s, find N.

Physics · Center of maas , Momentum and Collision · impuse and question based on it

G1 Physics · Accepted Answer

The wall is smooth, so the tangential velocity component remains unchanged. The normal component of the incident velocity is u(normal) = 10cos60° = 5 m/s toward the wall. For a perfectly elastic collision with a fixed wall, the normal component reverses from +5 m/s toward the wall to 5 m/s away from the wall, so its change in magnitude is 10 m/s. Therefore impulse magnitude is J = m×10 = 2×10 = 20 N·s. Hence N = 20.