Question

A $5g$ bullet was fired horizontally into a $1.2kg$ wooden block resting on a wooden surface. The coefficient of kinetic friction between the block and surface is $0.2$. The bullet remained embedded in block. The block was found to slide $0.23m$ along the surface before stopping. Find the initial speed of the bullet.

• A. 241 ms${}^{-1}$
• B. 229 ms${}^{-1}$
• C. 221 ms${}^{-1}$
• D. 202 ms${}^{-1}$

Answer 1

The correct option is B 229 ms${}^{-1}$

Using law of conservation of momentum

$v^{\prime }=\frac{5v}{1205}=\frac{v}{241}$ and $v^{\prime 2}=2as$

$\therefore {\left(\frac{v}{241}\right)}^2=2\times .2\times .23\times 10$

$v=\sqrt{241\times 241\times .92}=229$ ms${}^{-1}$