PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
Two identical wooden blocks P and Q, each of mass 2\,kg, are arranged one over the other on a rough horizontal table. The coefficient of static friction between the two blocks is 0.40 while that between the lower block Q and the table is 0.30. A horizontal force F is applied to the lower block Q and is increased gradually from zero.
(i) Draw separate free-body diagrams for blocks P and Q naming every force acting on them.
(ii) Explain, with reasons, the condition under which the two blocks will move together without any slipping between them.
(iii) When F is increased slowly, predict which contact surface (P–Q or Q–table) will first reach its limiting value of static friction. Justify your answer qualitatively without using numerical calculations.