posted by mayrel .
box full of books rests on a wooden floor. The normal force the floor exerts on the box is 235 N.
a) You push horizontally on the box with a force of 121 N, but it refuses to budge. What can you say about the coefficient of static friction between the box and the floor?
(b) If you must push horizontally on the box with a force of at least 135 N to start it sliding, what is the coefficient of static friction?
(c) Once the box is sliding, you only have to push with a force of 118 N to keep it sliding. What is the coefficient of kinetic friction?