Question

The minimum distance required to stop a car moving at 46.0 mi/h is 39.0 ft. What is the minimum stopping distance for the same car moving at 80.0 mi/h, assuming the same rate of acceleration?

Can I do a proportion or is this totally different?

Answer 1

I assume they mean the rate of DEceleration is the same. The time required to stop will then be larger by a ratio 80/46. Stopping distance is proportional to time x (average velocity), or (80/46)^2.

That makes the answer 39 ft x (40/23)^2