Question

Let’s say a thief is running on a train with 12 km/h. The police car is moving with 80
km/h. If speed of the train is 60 km/h. What is the speed of thief w.r.t police car?

Answer 1

first of all, let us find the speed of the thief with respect to ground

as he is on the train he posses the speed of the train and he too is running

at a speed of 12km/h

so his speed respect to ground is 12+60 =72

the speed of police car with respect to ground is 80km/h

the thief and police car are moving in the same direction

the relative velocity of thief w.r.t police car 72 - 80 = -8km/h

therefore the speed of thief w.r.t police car = 8km/h