Which vehicle requires a longer braking distance to stop at 55 mph?

Which vehicle requires a longer braking distance to stop at 55 mph?

• A. Automobile
• B. Motorcycle
• C. Tractor-trailer
• D. Bicycle

Answer: (C)

When you stop a vehicle, the energy you have to dissipate is tied to momentum: more mass at the same speed means more momentum and a longer time and distance to come to a complete stop. A tractor-trailer weighs far more than an automobile, a motorcycle, or a bicycle, so at 55 mph it has much greater momentum. Even with brakes doing their job, you have to overcome that extra momentum, which takes more distance. The truck’s longer wheelbase and the load it carries can also reduce braking efficiency and contribute to a longer stopping distance. Lighter vehicles have less momentum and thus stop more quickly under the same conditions. So, at 55 mph, the tractor-trailer requires the longest braking distance.

When you stop a vehicle, the energy you have to dissipate is tied to momentum: more mass at the same speed means more momentum and a longer time and distance to come to a complete stop. A tractor-trailer weighs far more than an automobile, a motorcycle, or a bicycle, so at 55 mph it has much greater momentum. Even with brakes doing their job, you have to overcome that extra momentum, which takes more distance. The truck’s longer wheelbase and the load it carries can also reduce braking efficiency and contribute to a longer stopping distance. Lighter vehicles have less momentum and thus stop more quickly under the same conditions. So, at 55 mph, the tractor-trailer requires the longest braking distance.