A disc of radius R rolls on a horizontal ground with linear acceleration $'a'$ and angular acceleration $' \alpha '$ as shown. The magnitude of the acceleration $'\alpha'$ of point P at an instant , when its linear velocity is V and angular velocity is $w$ will be,

Question

 

\[\begin {array} {1 1} (a)\;\sqrt{(a+r\alpha)^2+(rw^2)^2} & \quad (b)\;\frac{ar}{R} \\ (c)\;\sqrt {r^2a^2+r^2w^4} & \quad  (d)\;r \alpha \end {array}\]