Mass `m` is connected with an ideal spring of natural length `l` whose other end is fixed on a smooth horizontal table. Initially spring is in its natural length `l`. Mass `m` is given a velocity `'v'` perpendicular to the spring and released . The velocity perpendicular to the spring when its length `l+x` , will be

Options

A. `(2vl)/(l+x)`
B. `(2v^(2)+l)/(l+x)`
C. `(vl)/(l+x)`
D. zero

Answer

C

Explanation

since torque about `O` is zero.
angular momentum of mass `m` is conserved
`:. Mvl=mv_(_|_) (l+x), v_(_|_) =(vl)/(l+x)`