A block of wood of mass `3M` is suspended by a string of length `(10)/(3) m`. A bullet of mass `M` hits it with a certain velocity and gets embedded in it. The block and the bullet swing to one side till the string makes `120^@` with the initial position. the velocity of the bullet is `(g=10 ms^(-2))`.

Options

A. `(40)/(sqrt(3)) ms^(-1)`
B. `20 ms^(-1)`
C. `30 ms^(-1)`
D. `40 ms^(-1)`.

Answer

D

Explanation

`m u = (M + m) sqrt(2gl(1 - cos theta))`.