The stopping distance of a car is directly proportional to the square of the speed of the car. If a car traveling 40 mph has a stopping distance of 109 ft, find the stopping distance of a car traveling 25 Mph) (Round your answer to one decimal place.)
A) 42.6 ft
B) 55.4 ft
C) 68.1 ft
D) 49.0 ft

Question

Quizplus · Accepted Answer

The stopping distance $d$ is directly proportional to the square of the speed $v$, so $d = kv^2$ for some constant $k$. Given $d = 109$ ft at $v = 40$ mph, we find $k = 109 / 40^2$. For $v = 25$ mph, $d = k \cdot 25^2$, which calculates to approximately 42.6 ft.

The Stopping Distance of a Car Is Directly Proportional to the Square