Question

a student uses a force sensor to apply a force to a small box. initially the box is at rest and then after some time goes by it begins to move across the surface. at which labeled point below does the object experience a kinetic friction force?

Explanation:

Step1: Understand static and kinetic friction

Static friction acts when the object is at rest. Kinetic friction acts when the object is in motion.

Step2: Analyze the graph

At point A, the force is increasing but the box is still at rest (static friction). At point B, the force is at the maximum value (just about to overcome static friction). At point C, the box has started moving, so kinetic friction is acting.

Answer:

C