A body is hanging from a rigid support. by an inextensible string of length `'1'` . It is struck inelastically by an identical body of mass in with horizontal velocity `v=sqrt(2gl)` the tension in the string increases just after the striking by

Options

A. `mg`
B. `3mg`
C. `2mg`
D. none of these

Answer

C

Explanation

`mv=(m+m)v_(1)` or `v_(1)=v/2`
`T=(2mv_(1)^(2))/l+2mg=(2mv^(2))/(4l)+2mg`
`=(m(2gl))/(2l)+2mg=3mg`
Initial tension `= mg` increase in tension `=2mg`