2. In the right figure, with about what steady force must the man pull on the rope to achieve an upward acceleration of 0.50 m/s2? The man has a mass of70 kg and the chair has a mass of 10 kg. 
(A) 370 N
(B) 410 N
(C) 820 N
(D) 740 N
(E) 390 N.
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統計: 尚無統計資料
統計: 尚無統計資料