A weightless spring which has a force constant fr oscillates with frequency f when a mass m is suspended from it. The spring is cut into two halves and a mass 2 m is  suspended from one of the halves. The frequency of oscillation will now be:

• A

  f

• B

  2f

• C

  $\mathrm{f}/2^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$

• D

  $\mathrm{f}\times 2^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$