UPSEE Solved Model Paper 3

Since, the body rolls without sliding,

ap = 0 and vB = 0
⇒ V - rω = 0 and α - rα = 0
⇒ v = rω and a = rα
Since, the body acceleration 'a' is downwards parallel to the plane. Therefore, acceleration of the body must be in anti-clockwise sense. That means the friction must act up the plane to produce an anti-clockwise torque to produce anti-clockwise angular acceleration.