Worked examples
| Scenario | Speed | Cd·A | Drag force |
|---|---|---|---|
| Cyclist | 10 m/s | 0.4 | 25 N |
| Car | 30 m/s | 0.7 | 386 N |
| Same car, faster | 40 m/s | 0.7 | 686 N |
| Box truck | 25 m/s | 5.0 | 1,914 N |
Common questions
Why does drag rise so fast with speed?
Drag depends on velocity squared, so going from 30 to 40 m/s nearly doubles the force even though speed rose by a third.
What air density should I use?
About 1.225 kg/m³ at sea level and 15°C. Thinner air at altitude lowers drag.
