DPChallenge: A Digital Photography Contest You are not logged in. (log in or register) 
 

DPChallenge Forums >> General Discussion >> Plane and a Treadmill
Pages:  
Showing posts 276 - 286 of 286, (reverse)
AuthorThread
 02/01/2008 01:10:04 PM · #276
Originally posted by fir3bird:
Originally posted by Matthew:
The treadmill has a clever design and always matches the speed of the plane, but runs in the opposite direction.


The key sentence. If the treadmill always matches the speed of the plane you could accelerate with a 1,000,000 pound thrust engine and never out run the treadmill. Therefore no airspeed. No flight.

It's interesting looking at all the replies and comparing some of them with their arguments on Global Warming/Climate change.


I thought that the trick was in the theoretical nature of the treadmill too (meaning you couldn't ever truly construct a treadmill like this), but answer me this: how does the treadmill stop the plane? Recall that the wheels of a plane are not attached to any sort of drive. They just spin.
 02/01/2008 01:15:47 PM · #277
This thread is going to be the death of me. I would put it on ignore, but I simply can't deprive myself of the entertainment (as painful as it is).

I would like to reiterate a couple of points:

1. The question is worded in such a way as to lead the average reader to the wrong conclusion.
2. With the question worded as it is, it is a proven fact that the plane will take off.
3. For the love of whatever you believe in, if you don't think it will and truly want to understand why it actually does, please read the explanations in this thread. Don't give up, they are there.
 02/01/2008 01:51:26 PM · #278
Originally posted by DrAchoo:

I thought that the trick was in the theoretical nature of the treadmill too (meaning you couldn't ever truly construct a treadmill like this), but answer me this: how does the treadmill stop the plane? Recall that the wheels of a plane are not attached to any sort of drive. They just spin.


It's all in the wording. They should have never used the word speed. Of course if the plane is allowed to move through the air and generate lift the plane will fly. The wording carefully tries to confuse the issue. It makes most people think initially that the plane will not move.
This was the case with me.

Now for one that can happen in the real world:

A floatplane takes off on a river. Assuming river current is an unbelievable 30 mph, is takeoff easier upstream, or downstream? I bet a pilot residing in Washington state could answer that question.

Hhehehehe, put that in yer pipe and smoke it.

Edit: Oooops, maybe I should have put the last part in a
different thread. Nathan might have to be instituionalized.

Message edited by author 2008-02-01 13:53:39.
 02/01/2008 02:10:04 PM · #279
Originally posted by fir3bird:
A floatplane takes off on a river. Assuming river current is an unbelievable 30 mph, is takeoff easier upstream, or downstream?

Takeoff would be easier moving upstream. The plane needs to gain enough speed in the water for its floats to plane on the water (unfortunate homonym there) before it can gain the relatively frictionless thrust needed to achieve airspeed for takeoff. The floats will plane more quickly against the water current. That is the only difference though -- assuming that the air is still, and that the planing plane's movement is essentially frictionless against the water surface, in which case (as with the jet on the treadmill) the speed relative to the ground is irrelevant.
 02/01/2008 02:13:07 PM · #280
it would take off because the lift has nothing to with the ground. ie: the wheels aren't driven - they merely roll when the engines fire up.

just watch mythbusters.
 02/01/2008 02:18:03 PM · #281
The plane WILL takeoff.

There is no way for a treadmill to keep a plane from moving. Planes don't move from friction caused by the wheels spinning. The wheels spin as a result of the friction cause by the plane moving.

What would happen is that the plane would take off normally except that it's wheels would just be spinning way faster. Unless it blew out all its tires, it would takeoff just fine.

-------------------

As for the float plane, takeoff "easier" is the confusing factor. By easier do you mean in less distance or less overall energy used. It would take off in less distance going upstream for the reasons already stated (floats needing to plane on the water). However, overall energy expenditure may be less heading downstream.

[Double checked with some other aerospace engineers and they concur.]
 02/01/2008 02:20:11 PM · #282
it might be easier to keep the plane square with the river going with the current. making it easier in that respect.

02/01/2008 02:24:00 PM · #283
yes, it will take off. There are even examples on youtube where people show toy planes taking off on treadmills. No matter what the speed the treadmill is going, it won't effect the speed of the plane enough to make any difference.
 02/01/2008 03:34:19 PM · #284
the wheels on the plane will spin twice as fast as a normal take off and the plane takes off just fine.

I don't understand why this is so tough for some to understand?

Message edited by author 2008-02-01 15:34:33.
 02/01/2008 03:36:42 PM · #285
I got through three pages and had to jump the the (current) end.

Forgive me if this illustration has already been made, but I think I have a question that will help us all get to the proper answer to this whole treadmill business:

Suppose you have a helicopter with pontoon supports (floats).
Furthermore, suppose said copter is resting in a giant toilet located in the northern hemisphere.
Further furthermore, suppose said toilet when flushed has a magical whirlpool that automatically spins at a speed matching the primary rotors of the helicopter but in the opposite direction. The helicopter attempts to take off and the toilet flushes, spinning in the opposite direction of the rotors and at the same speed as the rotors.
Will the helicopter fly?

Chuck Norris could get that plane off the ground...
 02/03/2008 07:57:00 PM · #286
Originally posted by thomaspeople:
I got through three pages and had to jump the the (current) end.

Forgive me if this illustration has already been made, but I think I have a question that will help us all get to the proper answer to this whole treadmill business:

Suppose you have a helicopter with pontoon supports (floats).
Furthermore, suppose said copter is resting in a giant toilet located in the northern hemisphere.
Further furthermore, suppose said toilet when flushed has a magical whirlpool that automatically spins at a speed matching the primary rotors of the helicopter but in the opposite direction. The helicopter attempts to take off and the toilet flushes, spinning in the opposite direction of the rotors and at the same speed as the rotors.
Will the helicopter fly?

Chuck Norris could get that plane off the ground...


Sure, why wouldn't it fly? The rotors would spin at the exact same speed as they usually do, just the bottom would spin as well. With the rotors spinning at the appropriate speed to generate enough lift to lift the weight of the aircraft, it would still go up. Although the people inside would be screwed because it would be out of control at the point of takeoff. Hence the need for a tail rotor on helicopters, to counteract the rotational force of the rotors on the body. So I guess with a powerful enough tail rotor, the body of the helicoptor wouldn't spin either. :) Point of the matter is that the airspeed is irrelavant of the ground speed.

I think someone posted an example earlier in this thread about an airplane taking off on a giant sheet of ice (assume ZERO friction on the ice). Would it still take off? Sure, cause the wheels don't need to roll at all, all they'd do is slide. Would a car move? Absolutely not, and I'm sure everyone in the colder areas of the world can vouch for that personally. Now what about a plane coming to land on that infinitely long sheet of ice? Would it be able to stop? Eventually, yes. When deploying air brakes and the overall aero drag of the airframe, it would eventually stop. It would stop a lot faster if the wheels could provide braking forces, but there is no friction to act on so they do nothing. I guess I'm just trying to say that in the case of an airplane, the wheels mean nothing other than to reduce the friction force of the plane on the ground. Heck, you could take an airplane without wheels, lay it on the ground, and with enough thrust it would still take off (assuming no damage to it)

Message edited by author 2008-02-03 19:59:38.
Pages:  
Current Server Time: 06/19/2025 07:16:23 PM

Please log in or register to post to the forums.


Home - Challenges - Community - League - Photos - Cameras - Lenses - Learn - Help - Terms of Use - Privacy - Top ^
DPChallenge, and website content and design, Copyright © 2001-2025 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 06/19/2025 07:16:23 PM EDT.