Originally Posted by
IFlyRandom
...In your car, if you get to above 40 mph (to clearly experience the effect) and stick your hand out the window (forearm PARALLEL the car for better experience), your hand and arm will be pushed UP and BACK. The BACK part of pushing is the induced drag. As simple as that.
Well, not quite. There are many forms of drag and induced drag is only one type. As an easy experiment, the hand-out-the-window technique is unable to distinguish between them. Form, parasite, and induced drag are all there in the mix, a big part of it in this experiment is form drag. I do not know any simple experiments that will show only induced drag isolated from the others, because any lifting surface will carry along with it some of the others. It is true that if you vary the angle of your hand while driving, you can discern a big difference in the pull backwards, which is coming from the induced drag. But the hand-in-the-wind experiment has a lot of form drag, because a hand is bluntly shaped. A piece of painted balsa wood would have less form drag.