A Bullet Mass = M) Is Fired at Speed V

Multiple Choice

A bullet mass = m) is fired at speed V into a block of mass M with M > m) which is hanging vertically from a light string of length L. The bullet stops in the block. If the recoiling block + bullet system reaches a height of 2/3L, then the initial speed of the bullet is given by

A) M  1gL/3) ^1/2/m.
B) M  2gL/3) ^1/2/m.
C) M  3gL/4) ^1/2/m.
D) m  4gL/3) ^1/2/M.
E) M  4gL/3) ^1/2/m.