Solve the following :
Question:

A bullet of mass $20 \mathrm{~g}$ moving horizontally at a speed of $300 \mathrm{~m} / \mathrm{s}$ is fired into a wooden block of mass $500 \mathrm{~g}$ suspended by a long string. The bullet crosses the block and the block rises through a height of $20.0 \mathrm{~cm}$, find the speed of the bullet as it emerges from the block.

Solution:

Use C.O.L.M

$300(0.02)=0.5 . V^{\prime}+0.02 V$

From C.O.E.L,

$\frac{-1}{2} 0.5 V^{\prime^{2}}=-0.5 g(0.2)$

$V=\frac{300 \times 0.2-0.5 \times 2}{0.02}=250$