Question

8. (25 points) Pulley A rotates with the angular velocity and angular acceleration shown. Determine the acceleration of block E at the instant shown. 50 mm OA = 40 rad/s αΑ 5 rad/s2 50 mm B 125 mm E

You provided the following answer:

I don't understand why you ignore the vertical acceleration in point D? Why are you assuming that aDt = 0?

I think there is a vertical acceleration in point D ...

Could you explain this?

Answer 1

The portion of the cable between the ceiling and the pulley B is at rest .Hence the point of the pulley B where the cable leave it i.e point D is at rest.The cable is thus rolling without slipping on the cable .Hence point D is called I.C ( Instantaneous centre of rotation ).Hence point D has zero vertical acceleration but have centripetal acceleration .