# Speed of a rolling wheel confusion

Let there be a wheel which rotates around an axis , just like that

I am trying to calculate the angular momentum about point P. To make matters simpler, let's say that the wheel is slipping, that is, it isn't rolling and that it has zero thickness, it is two-dimensional.

My question is, is it correct to state that the velocity of the whole wheel is the same as the velocity of its center of mass?

I'm not sure about it because, since the axle is precessing with angular velocity $\Omega$ and the wheel is attached to the axle, it must be moving as well with angular velocity $\Omega$. Consequently the velocity of every part of the wheel must depend on its position.

• Different points in the wheel will have different velocities at different times. Mar 26, 2018 at 13:18
• @Mauricio Yes, I know. But what about at the same time? Is the wheel moving as a whole or isn't it? Mar 26, 2018 at 13:26
• If the wheel doesn't rotate every point in the wheel would have the same velocity. Mar 26, 2018 at 13:54
• If there’s no friction, treat the whole wheel as a point(center of mass). If there is friction consider the velocity of the wheel. Mar 26, 2018 at 14:03
• @physics2000 But if I do so, then the wheel isn't precessing at the same speed, there are some points thereof which are slower. Mar 26, 2018 at 14:06