0-m massless rod is loosely pinned to a frictionless pivot at 0.

A 8.0-m massless rod is loosely pinned to a frictionless pivot at 0. A 4.0-kg ball is attached to the other end of the rod. The ball is held at A, where the rod makes a 30 angle above the horizontal, and is released. The ball-rod assembly then swings freely in a vertical circle between A and B. In Fig. 7.1b, the tension in the rod when the ball passes through the lowest point at D is closest to: