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An automobile, travelling at 40 km/h, can be stopped at a distance of 40 m by applying brakes. If the same automobile is travelling at 80 km/h, the minimum stopping distance, in metres, is (assume no skidding)

1. 75 m
2. 160 m
3. 100 m
4. 150 m

Correct answer: 160 m

Solution

The stopping distance of a vehicle is proportional to the square of its speed. Therefore, if the speed doubles from 40 km/h to 80 km/h, the stopping distance increases by a factor of four, resulting in a new stopping distance of 160 m.

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