The Total solution for NCERT class 6-12
A police van moving on a highway with a speed of 30 km h–1 firesa bullet at a thief’s car speeding away in the same direction with a speed of192 km h–1. If the muzzle speed of the bullet is 150 m s–1,with what speed does the bullet hit the thief’s car? (Note: Obtain that speedwhich is relevant for damaging the thief’s car).
Speed of the policevan = 30 km/h = 30 x (5/18) = 25/3 m/s
Speed of a thief’s car= 192 km/h = 192 x (5/18) = 160/3 m/s
Muzzle Speed of the bullet = 150 m/s
Speed of the bullet =speed of the police van + muzzle speed of the bullet
= (25/3)+ 150 = 475/3m/s
The relative velocityof the bullet w.r.t the thief’s car is
v = Speed of thebullet – Speed of a thief’s car
= (475/3) – (160/3) =105 m/s
The bullet hits thethief’s car at a speed of 105 m/s