A 2 kg trolley moving at 6 m/s collides with a stationary 4 kg trolley and they stick together. What is their common velocity?
Correct answer D. 2 m/s
Explanation
Momentum conservation: 2 × 6 = (2 + 4)v, so v = 12/6 = 2 m/s. Kinetic energy is not conserved here, but momentum is.
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