Q. A bullet emerges from a barrel of length $1.2\ m$ with a speed of $\ 640\ ms^{- 1}$. Assuming constant acceleration, the approximate time that it spends in the barrel after the gun is fired is
A) $4\ ms$
B) $40\ ms$
C) $400\ \mu s$
D) $1\ s$
Explanation
(a) $s = 1.2\ m$
$v = 640\ ms^{- 1}$
$a = ?;u = 0;\ t = ?$
$2\ as = v^{2} - u^{2}$
$\Rightarrow 2a \times 1.2 = 640 \times 640 \Rightarrow a = \frac{8 \times 64 \times 10^{3}}{3}$
$v = u + at\ \Rightarrow t = \frac{v}{a} = \frac{15}{4} \times 10^{- 3} = 3.75 \times 10^{- 3}\ s \approx 4\ ms$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.