A bullet of mass $50 \mathrm{~g}$ is fired with a speed $100 \mathrm{~m} / \mathrm{s}$ on a plywood and emerges with $40 \mathrm{~m} / \mathrm{s}$. The percentage loss of kinetic energy is :

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Aicharya · Accepted Answer

$\begin{aligned} \mathrm{K}_{\mathrm{i}} & =\frac{1}{2} \mathrm{~m}(100)^2 \ \mathrm{~K}_{\mathrm{f}} & =\frac{1}{2} \mathrm{~m}(40)^2 \ \% 	ext { loss } & =\frac{\left|\mathrm{K}_{\mathrm{f}}-\mathrm{K}_{\mathrm{i}}ight|}{\mathrm{K}_{\mathrm{i}}} 	imes 100 \ & =\frac{\left|\frac{1}{2} \mathrm{~m}(40)^2-\frac{1}{2} \mathrm{~m}(100)^2ight|}{\frac{1}{2} \mathrm{~m}(100)^2} 	imes 100 \ & =\frac{|1600-100 	imes 100|}{100}=84 \%\end{aligned}$

A bullet of mass $50 \mathrm{~g}$ is fired with a speed $100 \mathrm{~m} / \mathrm{s}$ on a plywood and…

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