A sailboat race is held on a river that runs directly North to South, with a current of 12 knots. A 25 mile race is held going downriver (south). The first heat is held early in the day when there is no wind. The second heat, also going downriver, is held later, when there is a 12 knot tailwind (from the North). In which heat are the fastest times recorded?

(In reply to re(2): solution by Charlie)

I know about tacking and that a boat can move into the wind (in effect).  However, I doubt that it is possible in still water to use a 12 knot wind to move > 12 knots into the wind, just like it is not possible to use the 12 knot wind to move with the wind faster than 12 knots.

I buy that it might be possible to go > 12 knots perpendicular to the wind but I just don't buy that the absolute value of the portion of velocity in the same direction as the wind can exceed the wind speed.  I am having a difficult time finding any information about this online but I think we could probably prove something from a better understanding of the physics involved.

Posted by Joel on 2007-02-14 20:51:35