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A car travelling at 50 km/h can be brought to rest by applying the brakes over a minimum distance of 6 m. If the same car is moving at 100 km/h, what is the least distance needed to stop it?

1. 12 m
2. 18 m
3. 24 m
4. 6 m

Correct answer: 24 m

Solution

With the same maximum deceleration, stopping distance d is proportional to v^2 (d = v^2/2a). Doubling the speed (50 -> 100 km/h) multiplies the distance by 4: 4 * 6 m = 24 m.

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