試題詳解

1.A 300N weight, 5m long rigid uniform ladder is leaning against a smooth vertical wall. A 750N weight man stands on a rung 4m up along the ladder from its base as shown in fig.1. What is the minimum coefficient of the statical friction between the ladder and the floor required to keep the system in equilibrium? The angle is 53.1° on a horizontal beam. (cos53.1° = 0.6, sin53.1° = 0.8)
(A)0.22
(B)0.42
(C)0.46
(D)0.54
(E)1.90