An intermittent-drive mechanism for perforated tape F consists of the link DAB driven by...

An intermittent-drive mechanism for perforated tape F consists of the link DAB driven by the crank OB. The trace of the motion of the finger at D is shown by the dashed line. Determine the magnitude of the acceleration of D at the instant represented when both OB and CA are horizontal if OB has a constant clockwise rotational velocity of 120 rev /min.