4. A ball of mass m, at one end of a string of length L, rotates in a vertical circle just fast enough to prevent the string from going slack at the top of the circle. The speed of the ball at the bottom of the circle is:


(A) (5gL)1/2
(B) (4gL)1/2
(C) (3gL)1/2
(D) (2gL1/2
(E) (gL)1/2

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