A cracker is thrown into air with a velocity of $10 {\mathrm{ms}}^{-1}$ at an angle of 45° with the vertical. When it is at a height of (1/2) m from the ground, it explodes into a number of pieces which follow different parabolic paths. What is the velocity of centre of mass, when it is at a height of 1 m from the ground? (Take, $\mathrm{g} = 10 {\mathrm{ms}}^{-2}$)

• A

  $4\sqrt{5}{ \mathrm{ms}}^{-1}$

• B

  $2\sqrt{5}{ \mathrm{ms}}^{-1}$

• C

  $5\sqrt{4}{ \mathrm{ms}}^{-1}$

• D

  $5{ \mathrm{ms}}^{-1}$