The Physics Trick That Makes These New Super Cars So Insanely Fast

People with fast street cars like to put them through their paces at the quarter-mile track. One way to get your quarter-mile time is to just buckle up and put the pedal to the metal. But if your car’s design is suboptimal, you won’t be taking home the bragging rights.

So here’s this week’s question: Can automotive engineers predict a car’s quarter-mile time using physics? And could the physics suggest some tricks to make a car faster? Yes and yes! Let’s see how.

Simple Model for an Accelerating Car

When a car launches off the start, its increase in speed is described by its acceleration (the rate of change of velocity). But according to Newton’s second law, to increase velocity, you need a force pushing in the direction of travel.

We can model the motion of a car with just three forces. There’s the downward-pulling gravitational force (= mass, m, times the gravitational field, g). There is also the interaction between the car and the road. It’s useful to split this into two forces: One, perpendicular to the ground, is called the “normal force” (F_N). It’s the resistance of the ground to gravity—what keeps a car from plunging to the center of the Earth. The other force, friction (F_f), acts parallel to the ground. Here’s a picture: