Question

The velocity of a bullet is reduced from $200\text{m/s}$ to $100\text{m/s}$ while travelling through a wooden block of thickness $10\text{cm}$. The retardation, assuming it to be uniform, will be

• A. $10\times {10}^4{\text{m/s}}^2$
• B. $12\times {10}^4{\text{m/s}}^2$
• C. $13.5\times {10}^4{\text{m/s}}^2$
• D. $15\times {10}^4{\text{m/s}}^2$

Answer 1

The correct option is D $15\times {10}^4{\text{m/s}}^2$

Given, $u=200\text{m/s},v=100\text{m/s},s=0.1\text{m}$
From third equation of motion we have,
$a=\frac{v^2-u^2}{2s}=\frac{(100{)}^2-(200{)}^2}{2\times 0.1}=-15\times {10}^4{\text{m/s}}^2$
Hence, the retardation of the body is $15\times {10}^4{\text{m/s}}^2$