Q. A cylinder rolls up an inclined plane, reaches some height, and then rolls down (without slipping throughout these motions). The directions of the frictional force acting on the cylinder are
A) Up the incline while ascending and down the incline while descending
B) Up the incline while ascending as well as descending
C) Down the incline while ascending and up the incline while descending
D) Down the incline while ascending as well as descending
Explanation
(b) When the cylinder rolls up the incline, its angular velocity $\omega$ is clockwise and decreasing
This require an anticlockwise angular acceleration $\alpha$, which is provided by the force of friction $(F)$ acting up the incline
When the cylinder rolls down the incline, its angular velocity $\omega$ is anticlockwise and increasing. This requires an anticlockwise angular acceleration $\alpha$, which is provided by the force of friction $(F)$ acting up the incline
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.