(a) The plane motion of a solid can be imagined as the combination of translation of the C.M. and rotation about C.M.


In the problem vc=v=constant, and the rolling is without slipping i.e, vc=v=ωR

toward the center of the wheel.
(b) Let the center of the wheel move toward the right (positive x-axis) than for pure tolling on the rigid horizontal surface, wheel will have to rotate in clockwise sense. If ω be the angular velocity of the wheel then ω=vc/R=v/R.
Let the point A touches the horizontal surface at t=0, further let us locate the point A at t=t,
