Question

The manager of a department store is pushing horizontally with a force of magnitude 200 N on a box of shirts. The box is sliding across the horizontal floor with a forward acceleration. Nothing else touches the box. What must be true about the magnitude of the force of kinetic friction acting on the box (choose one)? (a) It is greater than 200 N. (b) It is less than 200 N. (c) It is equal to 200 N. (d) None of those statements is necessarily true.

Short answer

The force of kinetic friction on the box is less than 200 N, and Option (b) is correct.

Step-by-step solution

Identify the given data

The magnitude of horizontal force,$F=200\text{N}$

The frictional force always acts in the opposite direction of the movement of the object. The applied force must be greater than the frictional force for the forward movement of the box.

Forces acting on the box

Two forces act on the box. The first is the kinetic frictional force, and the second is the horizontal force. The net force for the forward movement should be greater than zero. The box moves forward, so the magnitude of the horizontal force is greater than the kinetic frictional force. The force of kinetic friction on the box is less than 200 N.

Therefore, the force of kinetic friction on the box is less than 200 N, and Option (b) is correct.