A box of bananas weighing 36.5 N rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.39, and the coefficient of kinetic friction is 0.18.
(a) If no horizontal force is applied to the box and the box is at rest, how large is the friction force exerted on the box?
N

(b) What is the magnitude of the friction force if a monkey applies a horizontal force of 6.2 N to the box and the box is initially at rest?
N

(c) What minimum horizontal force must the monkey apply to start the box in motion?
N

Question

A box of bananas weighing 36.5 N rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.39, and the coefficient of kinetic friction is 0.18.
(a) If no horizontal force is applied to the box and the box is at rest, how large is the friction force exerted on the box?
  N

(b) What is the magnitude of the friction force if a monkey applies a horizontal force of 6.2 N to the box and the box is initially at rest?
  N

(c) What minimum horizontal force must the monkey apply to start the box in motion?
  N

anonymous · Answer

(a) If no horizontal force is applied to the box, then the net motion of the box is 0. Therefore, there cannot be any frictional force acting. F = 0 N.

(b) You can approach this problem by using the equation: F = uN
u in this case is the coeff of kinetic friction ; N is the normal force equal to the weight of the box mg.

(c) You can approach this problem by using the equation: F = uN
u in this case is the coeff of static friction ; N is again the normal force.
Calculate F to find the force to overcome.