A particle of mass 2 kg moves with speed 5 m/s. An impulse changes the direction of its velocity through 120°, but its speed remains unchanged. If the magnitude of the impulse is 10√N N·s, find N.
Physics · Center of maas , Momentum and Collision · impuse and question based on it
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Question

A particle of mass 2 kg moves with speed 5 m/s. An impulse changes the direction of its velocity through 120°, but its speed remains unchanged. If the magnitude of the impulse is 10√N N·s, find N.

G1 Physics · Accepted Answer

The initial and final momentum magnitudes are equal: p = mv = 2×5 = 10 kg·m/s. The angle between the initial and final momentum vectors is 120°. The impulse is the vector change in momentum: J = |p(final)−p(initial)|. Therefore J² = p²+p²−2p²cos120° = 100+100−200(−1/2) = 300. Hence J = 10√3 N·s, so N = 3.