Question

A bullet of mass `20 g` moving horizontally strikes a block of mass `480 g` suspended by a string of length `2 m`. If the collision is completely inelastic , the minimum velocity of bullet , so that the combined mass complete vertical circle should be
A. `100 m//s`
B. `150 m//s`
C. `200 m//s`
D. `250 m//s`

Answer 1

Correct Answer - D
`20 u = (20 + 480)v rArr v = (u)/(25)`
If the block completes the vertical circle , for this
`v ge sqrt(5 gL)`
`(u)/(25) ge sqrt(5 xx 10 xx 2)`
`u ge 250 m//s`
`u_(min) = 250 m//s`