A driver increases speed from 40 km/h to 120 km/h on the same road surface. By what factor does the braking distance increase?
Answer and explanation
Correct answer: D. 9 times
- Step 1: Braking distance is proportional to the square of the speed.
- Step 2: The speed is multiplied by 3, so the distance is multiplied by 3^2 = 9.
Answer
9 times.
Why not the others: The distance grows with the square of the speed, so a simple proportional factor, a doubled factor and a halved factor all fail.
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