5. A particle of mass m travels in a horizontal circle of radius R on a frictionless table. The centripetal force is provided by a string passing through a hole in the table attached to two blocks of equal mass M, as shown in the figure. If one hanging block is removed, what will the radius of the particle motion become?


(A) ∛(2)R
(B) ∛(2)R
(C) √2 R
(D) 2R
(E) None of the above.

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統計: A(0), B(1), C(0), D(0), E(0) #3858161

詳解 (共 1 筆)

#7432813
所以可以先用一個前提來判斷
拿掉一個重物後
拉力會變小
向心力會變小,所以會跑到較大的半徑
所以一開始的向心力由拉力提供
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而又因為繩子的拉力永遠指向洞口,所以角動量守恆
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所以把v'代入新的向心力公式裡
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