Drag Force
The fluid resistance force opposing the motion of an object moving through a liquid or gas.
Governing formula
Fd = ½ ρ v² Cd A
SI unit
N
In depth
At high speeds, drag scales quadratically with velocity (v²) and depends on frontal area (A) and aerodynamic drag coefficient (Cd).
Examples in the real world
Air resistance opposing high-speed bullet trains or aircraft.