Question

A bullet of mass $10gm$ strikes a target at a velocity of $400m/s$ and loses half of its initial velocity. The loss of kinetic energy in joule is:

• A. $800$
• B. $200$
• C. $400$
• D. $600$

Answer 1

The correct option is D $600$

$\Delta K.E=\frac{1}{2}m(V_{final}^2-V_{initial}^2)$

$=\frac{1}{2}\times {10}^{-2}\left(\right(\frac{400}{2}{)}^2-\left(400{)}^2\right)$

$=\frac{1}{2}\times {10}^{-2}\times 16\times {10}^4\times \frac{-3}{4}$

$=-600J$

$\Rightarrow$ Loss $=600J$