A block of wood is pulled by a horizontal string across a rough surface at a constant velocity with a force of 20 N. If the coefficient of kinetic friction between the surfaces is 0.2, what is the weight of the wooden block?
A) 20 N
B) 40 N
C) 75 N
D) 100 N
E) 10 N

Question

Quizplus · Accepted Answer

The force of friction is equal to the coefficient of kinetic friction multiplied by the normal force (which is the weight of the block in this case). Since the block moves at constant velocity, the force of friction equals the pulling force of 20 N. Therefore, 0.2 * weight = 20 N, solving gives weight = 100 N.

A Block of Wood Is Pulled by a Horizontal String