What is the physics behind a frisbee in flight?

Asked by: Alan Bernstein

Answer

A frisbee has the same shape, in side view, as an airplane wing: the curved uppper surface causes the air to move faster accross the top frisbee than it does across the 'flat' bottom, when the frisbee is thrown. The 'lift' is then produced by the pressure difference between the bottom and top sides of the frisbee - the lower pressure is on top and the higher on the bottom - therefore the net force on the frisbee will be up - producing the needed lift.

The turning of the frisbee mostly produces 'stability', that is the spinning keeps the frisbee level in flight due to the 'gyroscopic' effect, i.e. any spinning disc likes to stay spinning at the same angle.

You can see for yourself that the spinning has nothing to do with the actual 'flying' of the frisbee by noting that you can spin a frisbee in place, on a stick or whatever, and it will not 'lift up'. You also can see that the frisbee is still spinning at nearly 'full speed' when it finally hits the ground, so you have another piece of evidence that shows that the spinning doesn't lift the frisbee.
Answered by: Norm Frey