Question

In case of pure rolling what will be the velocity of point a of the ring of radius r

Answer 1

When an object performs pure rolling the contact point on the ground will remain at instantaneous rest

So now we have

velocity of the object at contact with ground is given as

$\vec v - r\vec \omega = 0$

$\vec v = r \vec \omega$

now speed of any point on the ring is vector sum of velocity of center of mass of the ring and tangential speed of the point on the ring

$\vec v_{net} = \vec v_{cm} + r\vec \omega$

so this vector sum of two velocity at any point will given net velocity of any point on the ring

Answer 2

here your ans. hope it helps