4. Mary throws a ball with 0.80 kg mass against a brick wall. The ball is moving horizontally to the left at 30 m/s when it hits the wall; it rebounds horizontally to the right at 20 m/s. The ball is in contact with the wall for 0.010 s. Find the impulse of the net external force on the ball during its collision with the wall.
(A) 40 N·m
(B) 40 N·s
(C) 8 N·m
(D) 8 N·s
(E) 800 J
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統計: 尚無統計資料
統計: 尚無統計資料