Eli5: How come cars With more than 10x the horsepower of a normal car only has a top speed that is about 2-3x higher than one of a normal car.

Question

Fx: The Bugatti Chiron has just under 1500hp and a top speed of MAX 500kmh, while a Volkswagen Golf has 150hp and a top speed of around 200kmh.

In: Physics

Answer 1

Power requirements don’t scale linearly with speed, they scale with the *cube* of speed which means that in a given car, traveling at 400kph requires 8x the power as traveling at 200 kph.

At high speeds the air resistance is what limits the car’s speed, the force from the air resistance scales with the speed squared (F_drag=0.5 * density * Velocity^2 * Drag Coefficient * Area). But power is work over time, and work is force times distance which means the power also scales with the speed so the end result is that the power needed goes up by the cube so you need *at least* 8x the power to double the speed because we’ve completely ignored other non-ideal effects like rolling resistance.