Doubling your speed affects stopping distance by about how many times?

Doubling your speed affects stopping distance by about how many times?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

When you come to a stop, the braking distance grows with the amount of energy you have to dissipate, and that energy is proportional to the square of your speed. With the same brakes and road conditions, doubling your speed makes the braking distance about four times longer because braking distance ∝ v^2. Since the reaction distance (distance traveled during the driver’s reaction time) increases linearly with speed, the total stopping distance ends up a bit more than four times longer, but the common rule of thumb is that it’s about four times as long when speed is doubled.

When you come to a stop, the braking distance grows with the amount of energy you have to dissipate, and that energy is proportional to the square of your speed. With the same brakes and road conditions, doubling your speed makes the braking distance about four times longer because braking distance ∝ v^2. Since the reaction distance (distance traveled during the driver’s reaction time) increases linearly with speed, the total stopping distance ends up a bit more than four times longer, but the common rule of thumb is that it’s about four times as long when speed is doubled.