A 29.0-kg block is initially at rest on a horizontal surface. A horizontal force of 71.0 N is required to set the block in motion, after which a horizontal force of 56.0 N is required to keep the block moving with constant speed.

(a)

(b)

Explanation:

According to Newton's second law:

Recall that the frictional force is related jointly with the coefficient of friction and normal force . Replacing in the above equation, we get the coefficient of friction:

(a) The  coefficient of static friction is related with the force required to set the block in motion:

(b) The  coefficient of kinetic friction is related with the force required to keep the block moving with constant speed: