A 2 kg cart at 3 m/s hits a 1 kg cart at rest and they stick together. What is their speed afterwards?
Answer and explanation
Correct answer: B. 2 m/s
- Step 1: Momentum is conserved: 2 x 3 = 6 kg m/s. Step 2. The combined mass is 3 kg, so v = 6/3 = 2 m/s. Answer: 2 m/s. Why not the others: Sticking together adds mass, so the speed falls but not by half.
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