A block of mass is pulled along a horizontal surface through a distance by a constant…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A block of mass m is pulled along a horizontal surface through a distance s by a constant force of magnitude F that makes an angle θ above the horizontal. The coefficient of kinetic friction between the block and the surface is μk. The block starts from rest.
(i) Obtain expressions for the work done by (a) the pulling force and (b) the force of kinetic friction during the displacement.
(ii) Hence write the expression for the net work done on the block in terms of F,θ,μk,m and s.
(iii) Using an appropriate principle, derive an expression for the speed v of the block after it has moved the distance s.
(iv) Evaluate the speed for m=5kg,F=40N,θ=30∘,μk=0.20 and s=8m. (Take g=9.8m s−2.)