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?

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Fort Collins, CO

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Last Updated 6/21/2009
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