On a dry road a car at 50 km/h needs 14 m to brake. What does the same car need at 100 km/h under the same conditions?
Answer and explanation
Correct answer: D. 56 m
- Step 1: Doubling the speed multiplies the braking distance by 4. Step 2. 14 x 4 = 56 m. Answer: 56 m. Why not the others: 28 m: this only doubles the distance and ignores the square law. 42 m: this triples the distance, not quadruples. 112 m: this applies eight times, a cube-like error.
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