A bullet is to be fired with a speed of `2000 ms^-1` to hit a target 200m away on a level ground. If `g=10 ms^-2` the gun should be aimed

Options

A. directly at the target
B. 5cm below the target
C. 5cm above the target
D. 2cm above the target

Answer

C

Explanation

Horizontal distance of target is 200cm
Speed of bullet `=2000 ms^-1`
Time taken by bullet to cover the horizontal distance
`t=200/2000=1/10s `
During `1/10 s`, the bullet will fall down vertically due to gravitational acceleration.
Therefore, height above the target, so that the bullet hits the target is
`h=ut+1/2 g t^2 =(0 times 1/2) +1/2 times 10 times (0.1)^2`
`=0.05 cm =5cm`