Indiana Bureau of Motor Vehicles Permit Practice Test

If you double your speed on a highway, how much does your braking distance increase?

1. Two times

2. Three times

3. Four times

4. Five times

The correct answer is: Four times

When you double your speed while driving, your braking distance increases by four times due to the physics of motion. Specifically, the stopping distance is influenced by the square of the speed. When a vehicle is traveling at a higher speed, the kinetic energy (energy of motion) increases. The formula for kinetic energy is proportional to the square of the speed, which means that if you double the speed, the kinetic energy becomes four times greater. In practical terms, this means that when you apply the brakes, you require a much longer distance to come to a complete stop because the vehicle is not only moving faster, but also possesses more energy that must be dissipated to halt the vehicle. Thus, the correct answer illustrates that as speed increases, the stopping distance increases at a greater rate, specifically by a factor of four when speed is doubled. In contrast, the other options do not accurately represent how braking distance is calculated in relation to speed. For example, if the increase were only two times, it wouldn’t adequately account for the increased kinetic energy; similarly, three or five times would not correctly reflect the mathematical relationship between speed and stopping distance.