Enter the density of a fluid (1.225 kg/m^3 for air), the speed, drag coefficient, and cross sectional area of an object undergoing motion to calculate the force of drag (air resistance) on that object.
Drag Equation Formula
The following equation is used to calculate the drag force acting on a moving object through a fluid. Most often this fluid is air, but this formula can be used for any fluid.
F = 1/2 * ρ * v² * A * cd
- Where F is the force due to drag
- rho (ρ) is the density of the fluid the object is moving through
- v is the velocity of the object
- A is the cross sectional area
- and cd is the drag coefficient.
One thing to keep in mind when using this equation is that the velocity should be the relative velocity of the object with respect to the fluid, since the fluid can also be moving.
The drag coefficient in this equation is almost always determined experimentally. There is computer software that can accurate estimate drag coefficients for simple objects, but for complex shapes is must be done experimentally.