[phil_20686]

Since gwnn's puzzle obtained such a good interest, i have placed a physics brainteaser for your enjoyment


A "Kat" is a vehicle where the wheels drive a propeller that pushes the vehicle forward. There is no engine, but the wheels are connected to the propeller by some form of gear box.

Should I place this on a flat surface, and allow it to move in the wind, is it possible for my vehicle to overtake the wind? In either case, what is the maximum velocity that the "Kat" can reach.

You are allowed to assume an idealised environment ie no dissipative forces.

A hint:

Spoiler

IN order to convince yourself that it is possible to sail faster than he wind in theory imagine you are sailing at an angle to the wind, you will accelerate until your compnent of velocity in the direction of the wind is equal to the velocity of the wind, so your total speed should you turn downwind will be faster than the wind. This was well known to sailors, for whom the angle to the wind at which you could get the fastest speed depended on the way that your ship was rigged.

[hotShot]

Hint:

[hrothgar]

phil_20686, on Sep 23 2010, 01:11 PM, said:

You are allowed to assume an idealised environment ie no dissipative forces.

As I recall, the the drag from the water is the limiting factor on the speed of a sailboat. If we truly get to ignore nasty little factors like friction, you could get a sailboat moving VERY fast. (Then again, if we're really ignoring friction a sailboat would topple over pretty darn click)

Your example is going to be a lot more complicated.

The lack of a keel is going to introduce all sorts of problems, as will issues related to wheels versus bearings.