How leverage lets a vehicle go faster than wind speed

[Halc]

Yep. So has pulling on a bicycle pedal making the bike go in the opposite direction.

Ah, but when it's going downwind the wheels do the energy input (exert drag) and the prop does the propulsion, sort of like the bike wheels making the pedals go instead of the other way around.

 

[berkeman]

Thread closed for Moderation...

Thread reopened while we search for the previous thread(s)...

 

[berkeman]

Hasn't this been covered already?

Multiple times, and I'd like to merge this new thread into the latest one, but I'm having trouble finding it. I seem to remember it was based on a good video about some bet that somebody won doing a test with a prototype. Anybody able to find it? Thanks.

 

[vela]

Multiple times, and I'd like to merge this new thread into the latest one, but I'm having trouble finding it. I seem to remember it was based on a good video about some bet that somebody won doing a test with a prototype. Anybody able to find it? Thanks.

Isn't that the video linked to in the OP of this thread?

 

[berkeman]

Isn't that the video linked to in the OP of this thread?

You think it was the same video? I'm not sure how to search on that. Plus, I seem to remember that the still picture for the video in the previous thread showed the vehicle sailing downwind on a desert flat of some kind, not faces...

 

[vela]

You think it was the same video? I'm not sure how to search on that. Plus, I seem to remember that the still picture for the video in the previous thread showed the vehicle sailing downwind on a desert flat of some kind, not faces...

The thread below?

https://www.physicsforums.com/threa...ckbird-exploring-wind-power-leverage.1009943/

 

[berkeman]

The thread below?

https://www.physicsforums.com/threa...ckbird-exploring-wind-power-leverage.1009943/

You are my hero! Thanks. Merging this new thread start by @Ranger Mike into that thread. Thanks vela.

 

[Halc]

You are my hero! Thanks. Merging this new thread start by @Ranger Mike into that thread. Thanks vela.

This topic is probably the better thread. But I found some older posts, but part of another general thread on wind powered land vehicles.
https://www.physicsforums.com/threa...ks-also-use-sails.1000632/page-2#post-6473245

I just did a search on "blackbird" "wind power" and all the good stuff came up

 

[A.T.]

Hasn't this been covered already?

Here the latest previous related discussion, which shows how counter-intuitive the basic mechanical principles behind it are to some, so it will come up again and again:
https://www.physicsforums.com/threa...king-physics-3rd-edition.1048870/post-6860418

 

[sophiecentaur]

To my experience, you can roughly divide people to two types of learners; those who tend to memorize things, and those who tend to understand things.

What do we mean by the word "understand"? Hard to say in the case of an on-going discipline like Science. To understand the present state of knowledge doesn't mean your picture will be the correct one in the future. It can only mean that you have arranged all the facts (at the time) in your mind in a way that's self-consistent and which allows you to extrapolate reliably and to predict accurately what will happen in new situations / experiments.

The depth to which the individual feels they can do that will vary. Many people feel that they understand something on the grounds of what they have merely memorised it but how many of us fully apply the criterion above before feeling we have understanding? (Some smart Alec on PF can come along and shatter that understanding so easily.)

Basic Maths is a field where I believe that we can justify saying that we 'understand' because we can repeat endless arithmetic problems and always get the right answer. But that's because it deals with axioms, I guess.