Drag Coefficient Calculator
Calculate the drag force on an object: F_d = 0.5 * Cd * rho * A * v^2, or solve for Cd from measured drag.
Drag Force
1.1515 N
Drag Force vs Drag Coefficient (Cd)
Formula
## Aerodynamic Drag Force Drag opposes the motion of an object through a fluid. ### Formula **F_d = 0.5 Cd rho A v^2** - *Cd* = drag coefficient (shape-dependent, dimensionless) - *rho* = fluid density - *A* = reference frontal area - *v* = velocity relative to fluid Common Cd values: sphere 0.47, streamlined body 0.04, flat plate 1.28, car 0.25-0.45.
Exemplo Resolvido
Sphere (Cd = 0.47) of cross-section 0.01 m2 in air at 20 m/s.
- 01F_d = 0.5 * 0.47 * 1.225 * 0.01 * 400
- 02F_d = 0.235 * 1.225 * 4
- 03F_d = 1.152 N
Perguntas Frequentes
Why does drag scale with velocity squared?
At moderate to high speeds, drag is dominated by inertial effects (pressure drag). The kinetic energy of deflected air grows as v^2, so the force does too.
What determines the drag coefficient?
Primarily the shape and surface roughness. Streamlined shapes direct flow smoothly with less separation, giving lower Cd.
Does Cd depend on Reynolds number?
Yes, especially for smooth objects. The drag crisis for a sphere occurs around Re = 500 000, where Cd drops sharply.
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