A girl exerts a 36-N horizontal force as she pulls a 52-N sled across a cement sidewalk at a constant speed. What is the coefficient of kinetic friction between the sidewalk and the metal sled runners? Ignore air resistance. Show steps please.

Question

anonymous · Answer

it is very easy. Assume that sled is on x axis. weight of the sled is 52N, and condition which is given above is "sled is moving at constant velocity horizontally, it means there's no y-axis and z-axis force. so girl exerts 36N to the sled and sled is moving constant speed. therefore sum of the force is zero. there's no other axis force except for x-axis. so "exert force = friction"

finally we get 

36=uN    (where N is normal force which is weight of the sled)

36=u(52)   ,    u = 36/52  (maybe you can get simple number)