Question

A bullet is fired from the gun with a speed of 1000 $m{s}^{-1}$ in 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 neglegible and g = 10 $m{s}^{-2}$

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

Answer 1

Answer: (D)

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