Tension at the Bottom A ball of mass m is attached to a string of length L and released fr...

Tension at the Bottom A ball of mass m is attached to a string of length L and released from rest at the point A in Figure. (a) Show that the tension in the string when the ball reaches point B is 3mg, independent of the length l. (b) Give a detailed physical explanation for the fact that the tension at point B is independent of the length l.

FIGURE