The crates A and B of mass mA = 50 kg and mB = 75 kg, respectively, are connected by a pul...

The crates A and B of mass mA = 50 kg and mB = 75 kg, respectively, are connected by a pulley system. The system is released from rest on the inclined surfaces for which θ = 30°. Friction between A and the inclined surface on which it slides is insufficient to prevent slipping, and friction between B and the incline on which it slides is negligible. The cables in the pulley system are inextensible, and the coefficient of kinetic friction between crate A and the horizontal surface is μk.

Determine the required value of μk so that the speed of B is 7 m/s after it slides 5 m down the incline.

Figure P4.115