A wooden block slides down a rough inclined plane of inclination with its speed…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A wooden block slides down a rough inclined plane of inclination 30∘ with its speed remaining constant throughout the motion. Four forces act on the block: (A) gravitational force, (B) normal reaction of the plane, (C) kinetic friction and (D) an externally applied force that keeps the speed constant.
(i) For each of the four forces (A–D) state whether the work done during the downward slide is positive, negative or zero. Support every choice with a short justification based on the directions of force and displacement.
(ii) Explain why the algebraic sum of the works done by all four forces must be zero for the given motion.