Question
Physics Question on Motion in a plane
A rifle shoots a bullet with a muzzle velocity of 500ms−1 at a small target 50 m away. To hit the target the rifle must be aimed: (Take g=10ms−2 )
A
exactly at the target
B
10 cm below the target
C
10 cm above the target
D
5 cm above the target
Answer
5 cm above the target
Explanation
Solution
We know that distance
(sd)=speed(v) !!×!! time(t)
⇒ t=vs
Given, v=500ms−1,s=50m
∴ t=50050=0.1s
From equation of motion, for vertical displacement
h=ut+21gt2
Given, u=0,t=0.1s
∴ h=21×10×(0.1)2=0.05m=5cm.
Hence, the rifle must be aimed 5 cm above the target.