# What factors effect the magnitude of the drag force?

Aug 5, 2017

See below.

#### Explanation:

Some factors that impact the magnitude of air resistance (drag) include the size and shape of the object, the velocity of the object and the air, and other properties of the air such as its viscosity, mass, and compressibility.

In fluid dynamics, the drag equation is a formula used to calculate the force of drag experienced by a moving object which is completely enveloped in fluid. We might typically think of "fluid" as being synonymous with "liquid," but fluids include both liquids and gasses (+ plasma, etc.).

Here is the equation for the drag force:

${F}_{D} = \frac{1}{2} \rho {v}^{2} {C}_{D} A$

where $\rho$ is the mass density of the fluid, $v$ is the flow velocity (relative to the object), $A$ is the reference area, and ${C}_{D}$ is the drag coefficient

Note that this equation is only valid under certain conditions (aren't they all!)

I think one of NASA's education websites gives a very good explanation, so I'll sumarrize the points from that.

Factors: the object, the motion, the air.

The Object

• geometry: size and cross-sectional shape

The Motion

• velocity of the air

• inclination of object to flow

The Air

• mass of the flow

• viscosity

• compressibility

See NASA education resources on drag for more in-depth explanations.