A horizontal block is acted upon by a force of fixed magnitude that can be applied…
PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A horizontal block is acted upon by a force of fixed magnitude F that can be applied either at 30∘ above the horizontal (pull) or at 30∘ below the horizontal (push). The surface has the same coefficient of static friction μs in both cases. Which statement describes which orientation will make the block start moving first?
(a) Pushing at 30∘ below the horizontal requires the smaller force to initiate motion.
(b) Pulling at 30∘ above the horizontal requires the smaller force to initiate motion.
(c) Both pulling and pushing require the same minimum force to initiate motion.
(d) Pulling at 30∘ above the horizontal actually needs a larger force because some of the pull is wasted in lifting the block.