# 13.1 Vehicle Drag

Recall from fluids that drag takes the form shown in Figure 13.2, being composed of a part termed parasitic drag that increases with the square of the flight velocity, and a part called induced drag, or drag due to lift, that decreases in proportion to the inverse of the flight velocity.

where

and

Thus

 or

The minimum drag is a condition of interest. We can see that for a given weight, it occurs at the condition of maximum lift-to-drag ratio,

We can find a relationship for the maximum lift-to-drag ratio by setting

from which we find that

and

and

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