A ball of mass 0.2kg strikes an obstacle and moves at 60° to its original direction. If its speed also changes from 20m/s to 10m/s, the magnitude of the impulse received by the ball is

• A

  $2\sqrt{7}\mathrm{Ns}$

• B

  $2\sqrt{3}\mathrm{Ns}$

• C

  $2\sqrt{5}\mathrm{Ns}$

• D

  $3\sqrt{2}\mathrm{Ns}$