- #26

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Need to distinguish between the point of contact and a point X on the ring that's currently in contact.But how does it explain that ##\omega h\tan\theta## doesn't come in play. I mean, if the point of contact is at rest, its net velocity must be zero i.e

$$v_{cm}+\omega h\tan\theta=\omega' r$$

I understand that the above is supposed to be incorrect but I just don't see why.

The velocity of X is the velocity of the centre of the ring plus the velocity of X relative to that. The velocity of the centre of the ring is ωr

_{e}; the velocity of X relative to that is -ω'r. But X is instantaneously stationary, so the sum of these is zero.

The point of contact, on the other hand, travels faster than the centre of the ring, in the ratio h tan θ to r

_{e}.