A body is rotated in air and is dropped on the floor slowly

Question

When a body is rotated with a constant angular velocity $omega$ and is dropped to ground, the friction should act as in the picture below
Now, because of the friction, the center of mass must accelerate forward and the body should continue moving forward until the friction stops acting when the velocity of the point of contact is 0. Hence the body should continue moving forward till infinity
But when I try this experiment with a pen, the pen stops after some time which seems to contradict what I think should happen. Where am I wrong?

Adrian Howard · Accepted Answer

When it first hits the ground, if it is rotating fast enough to exceed the co efficient of static friction, it will have kinetic friction while it is slipping. This will start it accelerating forward until it stops slipping. Then it will have rolling (static) friction with the ground. It will also have friction from air resistance. These frictions will act to slow its rotation until it eventually stops.

Correct answer by Adrian Howard on June 26, 2021

Bill N · Answer

There are two factors you haven't considered:

If the surface is not perfectly flat, bumps and ridges and other stuff (dirt, etc) will have non-horizontal interactions with the cylinder, exerting torque on the cylinder about the rotational axis opposite the angular velocity. While similar to air resistance (collisions with molecules), I believe this will be a much larger effect.  Try rolling a rod across carpet (lots of bumps and ridges) versus a linoleum or flat vinyl floor.

If the surface is not perfectly level, gravity will cause torque which could stop (or speed up) the angular motion.

A body is rotated in air and is dropped on the floor slowly

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