Question

A police jeep on a petrol duty on national highway was moving with a speed of 54km/hr. in the same direction. It finds a thief rushing up in a car at a rate of 126km/hr in the same direction. Police sub – inspector fired at the car of the thief with his service revolver with a muzzle speed of 100m/s. with what speed will the bullet hit the car of thief?​

Answer 1

Answer:

Speed of the police jeep = 54km/h

Now we will convert the speed from kilometers to meters

Speed of police jeep =54km/h

1km/hr =1000m/60x60sec=5/18 m/s

= 54 x5/18

=270/18

=15m/s

Therefore 54km./hr speed is equal to 15m/s

Speed of the police jeep = 54km/h=15m/s

Muzzle speed of the revolver hit by the police=100m/s

Total velocity of the bullet= Speed of the car + muzzle speed= 100m/s + 15m/s= 115m/s

Velocity of the thief’s car= 126km/h

= 126x 5/18

= 35m/s

Therefore 126km./hr speed is equal to 35m/s

Velocity of the thief’s car=126km/h= 35m/s

Relative velocity of the bullet with respect to thief=Total velocity of the bullet – Velocity of the thief’s car= 115m/s – 35m/s= 80m/s

So bullet will hit the car of the thief at a velocity 80 m/s

Answer 2

VPJ = 54km/hr = 15m/s VTC = 126km/hr = 35m/s

Muzzle speed of the bullet Vb = 100m/s

VCP = 35 – 15 = 20m/s. VCP = Velocity of car w.r.t. police

VBC= 100 – 20 = 80 m/s VBC = Velocity of bullet w.r.t car

Thus bullet will hit the car with a velocity 80m/s.