# Air Resistance

Written by Jerry Ratzlaff on . Posted in Classical Mechanics

Air resistance or drag coefficient, abbreviated as Fa, is a force that opposes an object as it moves through the air.  This force is dependant on the velocity, area and the drag coefficient. As the velocity increases, the force increases by a square.  So if velocity doubles, the resistance increases by four (22).

### Air Resistance formula

(Eq. 1) $$\large{ F_a = k\;v^2 }$$

(Eq. 2) $$\large{ F_a = \frac{\rho \;C_d\; A}{2} \; v^2 }$$

Where:

$$\large{ F_a }$$ = force of air resistance or drag

$$\large{ A }$$ = area cross section of the object

$$\large{ \rho }$$ (Greek symbol rho) = atmosphere density object moves through

$$\large{ C_d }$$ = drag coefficient

$$\large{ k }$$ = a constant that collects the effects of area, density, and drag

$$\large{ v }$$ = velocity of the moving object