Re: [Phys-L] Impossible vehicles.

[David Bowman <David_Bowman@georgetowncollege.edu>]

Regarding:

> The physics of sailing upwind is the same as sailing downwind faster than
> the wind.
> This is discussed in some detail, using a couple of different approaches, at
> https://www.av8n.com/physics/sailing-upwind-downwind.htm
>
> Some useful diagrams are included.

JD's discussion in his above link and the Donald E. Simanek reference therein are quite valuable.  Of course a cute implication of all this is it's quite possible to sail both upstream in a river in perfectly calm air (relative to the ground), and to sail downstream faster than the current in the same calm conditions.  The first situation is a form of sailing downwind faster than the wind, and the 2nd is a form of sailing directly upwind.

David Bowman