Short · Driving
Why does twice the speed need four times the braking distance?
At fixed grip, reaction distance grows with speed while braking distance grows with speed squared. From 50 to 100 km/h, one doubles and the other quadruples.
Try it yourself
Opens Stopping Distance. Change the same thing yourself.
Transcript
Why does a car going twice as fast need four times as far to brake? Stopping happens in two parts. First, reaction. The car keeps rolling while the driver notices and moves to the brake. Then braking, which has to soak up the car's energy, and that energy grows with the square of speed. Now double the speed. The reaction distance doubles, but the braking distance quadruples. A self-driving car can shrink the reaction part. It can't cheat the braking part. Follow to see how the world works.