Q 11-05-027NEETEAMCET 2011 (Medical)Medium
A bullet is fired normally towards an immovable wooden block. If it loses $25\%$ of its kinetic energy in penetrating the block at thickness $x$, the further distance penetrated by the bullet into the block is
Answer: (C) $6x$
With a constant resisting force $F$, the energy lost is proportional to the distance.
$25\%$ of the KE is lost in distance $x$. The remaining $75\%$ is three times as much, so it is lost over a further $3x$.
Solution by Sreeraj P, M.Sc Physics