A wooden block of mass rests on a horizontal rough table
PHYSICS · Subjective · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A wooden block of mass m rests on a horizontal rough table. A student intends to make the block just start sliding by applying a force of magnitude F at an angle θ above the horizontal.
(i) State the limiting value of static friction acting on the block in terms of the normal reaction.
(ii) Explain, with the help of the vertical component of the applied force, how the magnitude of the normal reaction differs when the block is (a) pulled upward at an angle θ and (b) pushed downward at the same angle.
(iii) Using your explanation in part (ii), discuss qualitatively which of the two actions—pulling upward or pushing downward—would generally require a smaller magnitude of F to set the block in motion. Give reasons for your answer.