Consider a cylinder on top of inclined plane with angle x = 30 degrees. Now let the coefficient of friction is tan 30. What will be the motion of the body. It seems that either of the two will occur (assume perfectly leveled plane)

The friction is up the plane and provides angular acceleration however the net force is zero. And the kinetic energy of the body keeps on increasing constantly or does froction immediately change direction and body starts rolling down the plane ?

In either case it seems somehow the laws of physics are failing only if we assume normal reaction to pass through some other point other than centre of mass only then it makes sense?

I guess my confusion is whether the friction akes up its maximum value or does it take smaller value so as to meet no slip condition


marked as duplicate by sammy gerbil, John Rennie, Yashas, Kyle Kanos, peterh May 7 '17 at 11:54

This question was marked as an exact duplicate of an existing question.

  • $\begingroup$ -1. No research effort. There are many questions on this site which deal with friction on objects sliding or rolling down inclined planes. $\endgroup$ – sammy gerbil May 7 '17 at 9:23

It seems as though you aren't accounting for the friction force. Yes, the normal force passes through the center of mass of the cylinder, but the friction force acting along the plane at the point of contact does not pass through the center of mass. This in conjunction with the weight is what drives the motion down the plane.

The kinetic energy will increase as the object travels down the plane and loses its gravitational potential energy.


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