Question

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

• A. $15\times 10^{4}m/s^{2}$
• B. $13.5\times 10^{4}m/s^{2}$
• C. $12\times 10^{4}m/s^{2}$
• D. none of these

Answer 1

Answer: (A)

$15\times 10^{4}m/s^{2}$

Answer 2

Here : Initial velocity $=200\, m / s$ Final velocity $(v)=100\, m / s$ distance $s=10\, cm =0.1\, m$ Using the relation of equation of motion $v^{2} =u^{2}+2 a s$ $a =\frac{v^{2}-u^{2}}{2 s}=\frac{(100)^{2}-(200)^{2}}{2 \times 0.1}$ $=\frac{10000-40000}{2 \times 0.1}=\frac{-300000}{2}$ $=-150000\, m / s ^{2}$ $-15 \times 10^{4} m / s ^{2}$ (-) minus sign denotes retardation