Two cars moving in the same direction with the same speed of 30 kph at a distance of 5 km from each other. A 3rd car moving in the opp. direction meets these two cars at an interval of 4 minutes. Find the speed of 3rd car.
why can't we just solve this qs as -
Speed = distance/time
Hence, speed of 3rd car = 5000/4×60 = 20.83
Why is taking relative velocity necessary??

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Solution

velocity of A wrt C = va-vc

at time t=0 car C met car B

at t=4/60 hrs. car A will meet Car C.

distance traveled by Car A = 5km

=> 5= (Va-Vc)4/60

300/4= 30- Vc

75- 30 = - Vc

Vc = -45 kmph

. (- shows opposite

direction)

Here the velocity is a vector quantity that means it has both direction and magnitude.since the cars are in opposite direction the vector should be consider it's directional representation also.there for for considering the direction of the vehicles it is important to take the relative velocity in this type questions.

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