Question

The distance it takes a car to come to a complete stop after the brakes are applied is related to the speed that the car is traveling. The stopping distances and speeds are shown in the table below.

Stopping Distance of a Car vs. Speed
Stopping Distance, d (in feet)
Speed, s (in miles per hour)
20
17.89
40
25.30
60
30.98
80
35.78
100
40.00

Which equation best represents the data in the table?
s = 4 StartRoot d EndRoot
s = 0.37 d + 20
s = 13.7log(d)
s = StartFraction 1 Over 25 EndFraction d squared

Answer 1

s = 4√d

Check with the table (treating the first column as d = 20, 40, 60, ... and the second as s):
For d = 20: s = 4√20 = 4(4.472) ≈ 17.89
For d = 40: s = 4√40 = 4(6.325) ≈ 25.30
For d = 60: s = 4√60 = 4(7.746) ≈ 30.98

These match the table, so s = 4√d is the best representation.