- #1
TyloBabe
- 7
- 0
This is not a question from homework, but one about which I was curious. If a ball starts at rest at the top of frictionless plane, would it roll or slide down the incline?
The thing that confuses me is that it seems like it should just slide, since there is no friction and thus nothing to apply a torque. However, if you draw an instantaneous axis of rotation at the contact point between the incline and the ball, with the positive x-axis down the incline, and the y-axis in the direction of the normal force acting on the ball, then it would appear that the gravitational force acting on the ball's center of mass does apply a torque at the center of the ball (so a distance of radius=r away from the origin). Where am I wrong in this assumption?
The thing that confuses me is that it seems like it should just slide, since there is no friction and thus nothing to apply a torque. However, if you draw an instantaneous axis of rotation at the contact point between the incline and the ball, with the positive x-axis down the incline, and the y-axis in the direction of the normal force acting on the ball, then it would appear that the gravitational force acting on the ball's center of mass does apply a torque at the center of the ball (so a distance of radius=r away from the origin). Where am I wrong in this assumption?