A body of mass m travels along the x-axis with speed 2v and collides with a second body of mass 2m travelling along the y-axis with speed v. If the collision is perfectly inelastic, the percentage of kinetic energy lost in the collision is approximately:

56 %
62%
44%
50%

Correct answer: 56 %

Solution

Momentum components: px = m(2v) = 2mv, py = 2m(v) = 2mv, total mass = 3m. Final speed components give the combined KE, and comparing to initial KE yields about 56% loss.

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