Question

A bullet of 5 g is fired with a velocity of 800 m/s. The velocity of bullet becomes 200 m/s when it pierces a wooden block 2 m thick. What is the average resistance offered by the wooden block?

• A. 8.5 kN
• B. 7.5 kN
• C. 6.5 kN
• D. 30 kN

Answer 1

Answer: (B)

7.5 kN

Answer 2

From work-energy theorem Work done by resistance of block = change in KE
${{F}_{x}}=\frac{1}{2}m({{v}^{2}}-{{u}^{2}})$
$F=\frac{0.05\times [{{(800)}^{2}}-{{(200)}^{2}}]}{2\times 2}$
$F=7500N$
$F=7.5kN$