In a slider crank mechanism, the length of crank O2A is 65 mm, the length of connecting rod AB is 250 mm and the centre of gravity of the connecting rod is 65mm from the crank pin end. The crank rotates anti clockwise with uniform motion of 3000 r.p.m. Determine the acceleration of the wrist pin B and the acceleration of the centre of gravity of the connecting rod when the crank makes an angle of 450 with centre line connecting O2 and the wrist pin B.