Suppose we launch a disk so it rolls without slipping up an incline. The disk of course slows down as it moves up the incline. But in what direction does the friction force acting on the disk point?

Question

Quizplus · Accepted Answer

The friction force points up the incline because it opposes the direction of slipping. As the disk rolls up the incline without slipping, static friction acts in the direction opposite to the potential slipping direction, which would be down the incline, thus the friction force points up the incline to prevent slipping and support rolling motion.

Suppose We Launch a Disk So It Rolls Without Slipping