Question

A machine gun is mounted on an armored car moving with a speed of 20 ms${}^{-1}$. The gun can point aqainst the direction of motion of car. The muzzle speed of bullet is equal to speed of sound in air i.e., 340 ms${}^{-1}$.The time difference between bullet actually reaching and sound of firing reaching at a target 544 m away from car at the instant of firing is:

• A. 1.2 s
• B. 0.1 s
• C. 1 s
• D. 10 s

Answer 1

The correct option is B 0.1 s

Actual speed of bullet = 340 - 20 = 320 m/s

Distance between bullet and target = 544 m

Time for bullet to reach = 544/320 s

Time for sound to reach = 544/340 s

Time Difference = 0.1 s