試題詳解

4.Block A, with a mass of 10 kg, rests on a 30* incline. The coefficient of kinetic friction is 0.20. The attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. Block B, with a mass of 8.0 kg, is attached to the dangling end of the string (take √3 1.7 and g =10 m/s²). The acceleration of B is: 

(A) 0.72 m/s², up
(B) 0.72 m/s², down
(C) 2.6 m/s², , up
(D) 2.6 m/s², down
(E) 0 m/s²