# Wind Drag On A Car...

Estimate the drag force, in pounds, on a car with a coefficient
of drag of 0.32 and a frontal area of 25 square feet, traveling
through air at 55 mph. Then estimate the horsepower required to
maintain that speed.
DragForce = 1/2 * Cd * Density * Velocity Squared * Area
Power = Force * Velocity

## Without Calchemy

First we must convert the parameters to a coherent system of units
so we can actually use the equations. Note the density of air is 1.293 kg/m^3
First convert speed to meters.sec

Then square feet to square meters...

Plug into the equation and get force in Newtons...

Then convert Newtons to pounds force...

Now calculate the horsepower...

## Now the same calculation using Calchemy

Simple eh?

Calchemy Software Inc.

Fort Collins, CO

Last Updated 6/21/2009

© Copyright 1996-2009 Calchemy Software Inc.