Wow, Mythbusters just took off an airplane from a treadmill!
What can you say?
Tris
Was the plane moving forward, or were the wheels spinning with the treadmill?
I found the whole thing badly done and disappointing. At one point the announcer said something like “In a car, the wheels make it go forward. In a plane it is the engine” WTF? It’s the propeller pushing air vs the wheels pushing the pavement. They both have “engines”.
The funny part, though, was that the pilot thought he wouldn’t take off.
Thanks for the heads up, but I don’t think we’re going to find a debate as to whether Mythbusters aired such a show.
Off to MPSIMS.
[ /Modding ]
Link from the show’s website: http://mythbusters-wiki.discovery.com/page/Airplane+on+a+Conveyor+Belt±+Get+Exclusive+Photos%21
Both.
There’s a whole thread on this in Cafe Society.
Sailboat
OK, I expected a debate. I am perfectly happy with a MPSIMS or Cafe view of things.
What I found interesting was that it actually worked, with very minor glitches. It was not what I expected at all.
The wheels turned freely. The planes scale and life sized were unaffected, basically by the speed of the treadmill. I had expected it to be unable to reach speed, although looking at it now I wonder why I expected that. Airspeed and Ground speed are really quite independent, and propellers produce motion through air. Not really a surprise, yet, the pilot and I, and a lot of other people thought it would not take off.
It’s still a case of doing it, rather than talking about it, which I always support.
Tris
PS, if the other thread is better, let this one sink slowly into the muck at the bottom of MPSIMS.
Also, don’t forget the plan was an ultralight, did anyone see that? Those things only need like 30 feet to take off.
Do different laws of physics apply to ultralights?
Tris
85 feet at 25mph in the case of the particular ultralight used on the show.
Can we now officially make fun of people who argued so intensely that the plane couldn’t take off? Please?
Nitwits.
I still like to compare it to being on a treadmill on rollerskates and having a rope attached to a wall. You can speed that treadmill up as fast as you like but it’s not going to stop you from pulling yourself towards the wall using the rope.
I don’t think the intense arguments applied to a real plane on a real treadmill, it was about the assumptions made in the statement of the problem. With an ideal plane and treadmill it wouldn’t take off.
Yes, it would. Read the rollerskates+rope analogy. It works exactly the same way.
A key point in the original problem is that the plane’s wheels and the treadmill always match speed. That means that the wheels and treadmill would instantly go to infinite speed, everything would be destroyed, and it wouldn’t take off. Mythbusters didn’t meet that condition.
The beauty of the problem is that it has hidden traps in it for people with wildly different knowledge levels.
What happens when the friction of the wheel bearings in the skates causes so much backward force that the rope breaks?
The model plane moved forwards.
The ultralight was on a tarp being pulled by a truck and moved in relation to an observer standing still.
One thing I notice on the show, they were very careful to state that the treadmill (or equivalent) was moving, opposite the airplane, at a speed equal to the take off speed. They did not try to claim that the treadmill was exactly matching the actual speed of the airplane. I would love to see what the engine speed at take off was, treadmill vs non-treadmill. Did the plane actually just move faster the standard take off speed, and so wasn’t being matched by the treadmill?
Is this some sort of ideal aircraft, capable of producing infinite thrust? I think you’ve created one of those ‘unresistable force/unmovable object’ paradoxes.