Question

The average force necessary to stop a bullet of mass $20g$ moving with a speed of $250m/s$, as it penetrates into the wood for a distance of $12cm$ is

• A. $2.2\times {10}^{3}N$
• B. $3.2\times {10}^{3}N$
• C. $4.2\times {10}^{3}N$
• D. $5.2\times {10}^{3}N$

Answer 1

The correct option is D $5.2\times {10}^{3}N$

From equation of motion we can find its acceleration.

$v^2=u^2+2as$

$0=(250{)}^2+\frac{2a\times 12}{100}$

$a=\frac{62500\times 100}{24}$

$F^{\prime }=ma$

$F^{\prime }=\frac{20}{1000}\times \frac{62500\times 100}{24}=5208.3N$