Drag Grows with the Square of Speed

Air resistance is not a fixed force. For everyday objects it rises roughly with the square of speed, so doubling a cyclist's speed roughly quadruples the drag — and because power is force times speed, it demands about eight times the power. That one relationship explains why the last few km/h of top speed are so expensive, why vehicles are streamlined to keep the airflow attached rather than merely polished smooth, and why a parachute slows you by adding area rather than by adding weight.