Question

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

• A. 0.32
• B. 0.44
• C. 0.16
• D. 0.84

Answer 1

Answer: (D)

0.84

Answer 2

The initial kinetic energy of the bullet is:

$K_i = \frac{1}{2} m (100)^2$

The final kinetic energy of the bullet is:

$K_f = \frac{1}{2} m (40)^2$

The percentage loss in kinetic energy is given by:

$\% \text{loss} = \frac{|K_f - K_i|}{K_i} \times 100$

Substituting the expressions for $K_i$ and $K_f$:

$\% \text{loss} = \frac{\left| \frac{1}{2} m (40)^2 - \frac{1}{2} m (100)^2 \right|}{\frac{1}{2} m (100)^2} \times 100$

Simplify:

$\% \text{loss} = \frac{|1600 - 10000|}{10000} \times 100$

$\% \text{loss} = \frac{8400}{10000} \times 100 = 84\%$

Final Answer: 84% (Option 4)