A block weighing 20 N rests on a horizontal surface. The: coefficient of static friction between block and surface is 0.40 and the coefficient of kinetic friction is 0.20.
( a) How large is the friction force exerted on the block?
(b) How great will the friction force be if a horizontal force of 5 N is exerted on the block?
(c) What is the minimum force that will start the block in motion?
(d) What is the minimum force that will keep the block in motion once it has been started?
(e) If the horizontal force is 10 N, what is the friction force?