試題詳解

36. A small block of mass m rests on the sloping side of a triangular block of mass M which itself rests on a horizontal table as shown in the figure below. Assuming all surfaces are frictionless, determine the magnitude of the force F that must be applied to M so that m remains in a fixed position relative to M. Hint: 1. Take x and y axes horizontal and vertical. 2. Focus at the object m.

(A) mg sinθ 
(B) mg tanθ 
(C) (m+M)g tanθ
(D) (m+M)g sinθ
(E) None of these