Does this look familiar?

Estimate the drag force, in pounds, on a car traveling through air at 55 mph with a coefficient of drag of 0.32 and a frontal area of 25 square feet. Then estimate the horsepower required to maintain that speed.

Drag Force = 1/2 * Cd * Density * Velocity^2 * Area
Power = Force * Velocity

Note the density of air is 1.293 kg/m^3

Without Calchemy

First we must convert the parameters to a coherent system of units so we can actually use the equations

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...

The same calculations with Calchemy

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