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Doubt & Answer Explanation

Doubt

Ques . A car travelling at 60 km/h overtakes another car traveling at 42 km/h . Assuming each car to be 5 m long, find the time taken during the overtake and the totl road distance used for overtake .

Answer Explanation

Let us assume that the car travelling at 42km/h is at rest. Relative to this car then, the velocity of the overtaking car will be 18 km/h to the left.

Also, relative to the 42 km/h car, the 60 km/h car has to travel a distance of 10 m to overtake it. This is because the 60 km/h car will have completely overtaken the 42 km/h car only when its rear end overtakes the front end of the 42 km/h car.

So, applying - relative distance = relative speed x time, we have:

10 = 18 km/h(t). 18 km/h is 18 x 5/18 = 5 m/s.

So, 10 = 5(t) or t = 2 seconds.

Hence the 60 km/h car takes 2 seconds to overtake the 48 km/h car.

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