Multiple-Object Systems with Friction: Block a of Mass 5

Multiple Choice

Multiple-object systems with friction: Block A of mass 5.0 kg and block X are attached to a rope which passes over a pulley, as shown in the figure. An 80-N force P is applied horizontally to block A, keeping it in contact with a rough vertical face. The coefficients of static and kinetic friction between the wall and block A are μ_s = 0.40 and μ_k = 0.30. The pulley is light and frictionless. The mass of block X is adjusted until block A moves upward with an acceleration of 1.6 m/s². What is the mass of block X?

A) 9.9 kg
B) 9.3 kg
C) 8.7 kg
D) 8.1 kg
E) 7.5 kg