Neglecting reaction time, the distance required for a car to stop is directly proportional to the square of it

Question

Neglecting reaction time, the distance required for a car to stop is directly proportional to the square of its velocity. If a car can stop in 8.5 meters at 20 kilometers per hour, approximately how many meters are needed to stop at 50 kilometers an hour?

13.4

21.3

53.1

117.6

Answer 1

Since it is directly proportional we know:

(20km/hr)^2 * x = 8.5m

x = 0.0085km/(400km/hr)^2

x = 0.0000212

So at 50 km/hr

(50km/hr)^2 * 0.0000212 = 0.0053km = 53m

The answer is C

Answer 2

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