DWFTTW

[janszott]

Down Wind Faster Than The Wind.

Can a vehicle travel directly downwind faster than the wind, powered only by the wind? The instinctive answer is no but this link seems to show it is possible.

Lots of discussion on other forums and more videos on Youtube.
LINK

What do you think? Fact or hoax?

[shirt]

can't access youtube or video sites from work, but here's 2 links for those wondering what he's on about:

http://www.physicsforums.com/showthread.php?t=2700...

http://www.physicsforums.com/showthread.php?s=f847...


sounds a bit airplane/conveyor belt to me

[crofty1984]

No. For it to travel exactly as fast as the wind, ALL the kinetic energy must be transferred, which isn't possible. So FASTER than the wind? no.

[8Ace]

On this forum, we obey the LAWS OF THERMODYNAMICS!

Unless it's going down hill, but that means the "powered only by wind" bit is not strictly correct...

[Famous Graham]

Wind isn't fixed though, is it.

If it's blowing at, eg 20mph, and the vehicle hits that, then the wind drops to 10mph, for a brief period, it IS travelling faster than the prevailing gusts.

Edited by Famous Graham on Monday 12th January 16:28

[Chris_w666]

This is going to turn into another conveyor belt thread.

[JP_Midget]

http://www.cbsnews.com/stories/2008/12/15/sunday/m...

"On this day the wind was 20 knots (about 23 miles an hour). And the yacht was doing 30 knots (nearly 35 miles an hour)."

ETA - The physics behind this is fairly subtle, but what you could argue is that the yacht won't have been travelling 'down wind' as observed by a static veiwer. On board the apparent wind would have been pretty much to the rear though.

Edited by JP_Midget on Monday 12th January 16:47

[alsem]

JP_Midget said:

http://www.cbsnews.com/stories/2008/12/15/sunday/m...

"On this day the wind was 20 knots (about 23 miles an hour). And the yacht was doing 30 knots (nearly 35 miles an hour)."

ETA - The physics behind this is fairly subtle, but what you could argue is that the yacht won't have been travelling 'down wind' as observed by a static veiwer. On board the apparent wind would have been pretty much to the rear though.

Edited by JP_Midget on Monday 12th January 16:47

that's not directly down wind, I don't know any english sailing terms, but if you go down the wind with the same speed as the wind, the relative wind speed is 0.
If you go up the wind you can go faster then the wind, and have a relative wind speed that's even faster then your speed.

[Strawman]

I thought this was going to be about 'drifting for-the-win' in text speak