An open knife edge of mass M is dropped from a height 'h' on a wooden floor. If the blade penetrates a distance 'S' into the wood, average resistance offered by the wood to the blade is:

• A

  Mg

• B

  $\mathrm{Mg}\left(1+\frac{\mathrm{h}}{\mathrm{S}}\right)$

• C

  $\mathrm{Mg}\left(1-\frac{\mathrm{h}}{\mathrm{S}}\right)$

• D

  $\mathrm{Mg}{\left(1+\frac{\mathrm{h}}{\mathrm{S}}\right)}^2$