Question

A bullet of mass $200 g$ having initial kinetic energy $90 J$ is shot inside a long swimming pool as shown in the figure. If it’s kinetic energy reduces to $40 J$ within $1 s$, the minimum length of the pool, the bullet has to travel so that it completely comes to rest is

• A. 45 m
• B. 90 m
• C. 125 m
• D. 25 m

Answer 1

Answer: (A)

45 m

Answer 2

u = $\frac{1}{0.2}$ $\sqrt{2×0.2×90}$ = 30 $m/s$

v = $\frac{1}{0.2}$ $\sqrt{2×0.2×40}$ = 20 $m/s$

a=$\frac{20-30}{1}$ = -10 $m/s^2$

s = -$u^2/2a$ = 45 $m$