Question

A bullet is fired from the gun with a speed of $1000\, m/s$ m order to hit a target. $s = 100\, m$ away. At what height above the target should by gun be aimed? (The resistance of air is negligible and $ g=10\,m/s^{2}$ )

• A. 23 cm
• B. 15 cm
• C. 9 cm
• D. 5 cm

Answer 1

Answer: (D)

Here: Speed of bullet $v = 1000\, m/s$
Distance of target $s = 100\, m$
The time taken to cover the horizontal distance of $100\, m$ from the gun to the target is given by
$t=\frac{100}{1000}=0.1$ second
During this time, the bullet will fall down vertically under gravity
Hence, height $h=u t+\frac{1}{2} g t^{2}$
$=0 \times \frac{1}{2} \times 10 \times(0.1)^{2}$
$=5 \times 0.01=0.05\, m =5\, cm$