A 2.5 kg stone is released from rest and falls toward Earth. After 4.0 s, the magnitude of its momentum is (g = 10ms-2):
Correct answer: A. 100 kgm/s
- A. 100 kgm/s
- B. 50 kgm/s
- C. 98 kgm/s
- D. 49 kgm/s
Explanation
To solve this problem, first calculate the final velocity of the stone after 4.0 seconds using the formula for velocity in free fall: vf = vi + gt, where vi (initial velocity) = 0 m/s (since it was released from rest), g = 10 m/s², and t = 4.0 s. This gives vf = 0 + (10)(4) = 40 m/s. Next, calculate the momentum using the formula P = mv, where m = 2.5 kg and v = 40 m/s. Therefore, P = (2.5 kg)(40 m/s) = 100 kgm/s. Option A is correct. Options B, C, and D result from incorrect calculations of either velocity or momentum.
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