A bullet of mass $0.02\;kg$ travelling horizontally with velocity $250\;ms^{-1}$ strikes a block of wood of mass $0.23\;kg$ which rests on a rough horizontal surface. After the impact, the block and bullet move together and come to rest after travelling a distance of $40\;m$ . The coefficient of sliding friction of the rough surface is : $(g=9/8 ms^{-2})$

Question

$$\begin {array} {1 1} (1)\;0.75 & \quad (2)\;0.61 \\ (3)\;0.51 & \quad (4)\;0.30 \end {array}$$