A trunk with a weight of 210 N rests on the floor. The coefficient of static friction between the trunk and the floor is 0.40, while the coefficient of kinetic friction is 0.29. What is the minimum magnitude for a horizontal force with which a person must push on the trunk to start it moving?
There are two forms of friction, kinetic and static. If you try to slide two objects past each other, a small amount of force will result in no motion. The force of friction is greater than the applied force. This is static friction. If you apply a little more force, the object "breaks free" and slides, although you still need to apply force to keep the object sliding. This is kinetic friction. You do not need to apply quite as much force to keep the object sliding as you needed to originally break free of static friction.
Magnitude for a horizontal force: F=P*max(0,40;0.29)=210*0.4=84N