A student arranges a wooden block on a rough wooden plank that can be tilted…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A student arranges a wooden block on a rough wooden plank that can be tilted gradually about one edge. She wishes to measure the coefficient of static friction between the two wooden surfaces.
(i) Describe, step by step, how the student can perform this experiment using the tilting plank so that the block just begins to slide.
(ii) By analysing the forces acting on the block at the instant it is about to slide, show that the coefficient of static friction between the two surfaces is equal to tanθ, where θ is the inclination of the plank to the horizontal at that instant.
(iii) Explain why changing the apparent area of contact between the block and the plank does not change the value obtained for the coefficient of static friction.
(iv) Identify any two practical sources of error in this experiment and state how each one could be minimised.