Mythbusters tonight

[durrell]

Originally Posted by Mainerunr

I get what you're saying mountaineer, it's all in the wording and the way you're wording it, you are correct.

yes, a plane could take off even if on a moving treadmill.

but no, a plane cannot take off from said treadmill IF the wheels are spinning at the same speed so as to cover the exact same distance as the treadmill (ie wheels spinning at 200mph, treadmill moving 200 mph opposite direction) because if that were the case then the plane would actually NOT be moving (meaning it would be generating only enough thrust to overcome the friction in the wheel bearings.

everyone is looking at the can it take off and yes, it can but given the conditions specified by Mountaineer, no, it cannot.

It can take off regardless of the wheels or what the treadmill is doing. The thrust generated by the engines is dependent on the air behind the plane, not the wheels. The wheels may burn up because of the friction, but it doesn't matter..it's still able to move forward and take off. The physics and math have been solved and it will work. I really don't see how people can think it won't take off in any scenario of the treadmill. It doesn't matter if the treadmill is moving faster backwards or even at the same speed, the wheels have absolutely nothing to do with the plane taking off.

Edit: But like you said, this question is made so as to trip people up with different wording. I've always and will always say the plane takes off, though, regardless.

[silversuper]

dont the wings need to be moving through the air to take off?

wheels are erronious, some planes have skis.

[CT_Nismo]

Originally Posted by scuba91ta

to answer the longitude question, it better! otherwise the compass is off!

Compasses are aligned with magnetic north. If on this trip, the heading is south on the Prime Meridian, you would expect to end up in Greewich England. However, because the earth is rotating, you end up somewhere over the Atlantic.

[Mainerunr]

Originally Posted by durrell

It can take off regardless of the wheels or what the treadmill is doing. The thrust generated by the engines is dependent on the air behind the plane, not the wheels. The wheels may burn up because of the friction, but it doesn't matter..it's still able to move forward and take off. The physics and math have been solved and it will work. I really don't see how people can think it won't take off in any scenario of the treadmill. It doesn't matter if the treadmill is moving faster backwards or even at the same speed, the wheels have absolutely nothing to do with the plane taking off.

Edit: But like you said, this question is made so as to trip people up with different wording. I've always and will always say the plane takes off, though, regardless.

easy. if the treadmill is moving at 200 mph, and the wheels are moving 200 mph in the oppisite direction then the plane is actually NOT MOVING (meaning the engines are only doing enough to keep the plane stationary because the treadmill and wheels are moving at the same speed in opposite directions).

Yes, the plane can take off from a treadmill because what the treadmill is doing is irrelevant to what the engines are doing but

200mph ---->
<---- 200mph

means no movement relative to the air. its not about what the plane CAN do, it's about what the plan IS doing and in this case, it is not moving relative to the air because the movement of the treadmill and the movement of the wheels cancel each other. put it this way. if the plane needs to reach 200mph (relative to air) and the treadmill is moving 200mph in the opposite direction then the wheels would need to be moving at 400 mph before the velocity of the plane reaches the required 200mph for liftoff.

I've always said it will take off but the way the question is posed makes a huge difference.

Originally Posted by CT_Nismo

Compasses are aligned with magnetic north. If on this trip, the heading is south on the Prime Meridian, you would expect to end up in Greewich England. However, because the earth is rotating, you end up somewhere over the Atlantic.

why do people feel the need to do this? yes, it's off topic, that doesnt mean spam away. off topic means not frontier related, the posts still have a topic even if they dont have a point.

isnt there a spamwhore thread floating around for people to post random crap in?

[Autospirit]

I think some people are imaging that the plane is just supposed to hover up off the treadmill in the same location in which it began. It still need a proper distance to build up speed to generate lift, so this treadmill/runway needs to be long enough. The thrust from a jet engine doesnt care what it is sitting on. Be it 200mph on stable ground or 400mph on a treadmill, as long as the wheels can withstand the rpm's while the plane covers enough distance to generate lift, it makes no difference to the jet engine.

Edit. Pretend the wheels are frictionless. The plan can maintain its location on a 200mph treadmill without even using any kind of thrust. When it does begin to propell itself, it is no different than if it was sitting on stable ground

[Mountaineer]

The way I read the problem online was that the wheels and the treadmill are going the same speed. Yes, if the treadmill is long enough and the plane was going faster than the treadmill, it will take off, that's simple.

[fleaofsc]

Originally Posted by Mainerunr

I get what you're saying mountaineer, it's all in the wording and the way you're wording it, you are correct.

yes, a plane could take off even if on a moving treadmill.

but no, a plane cannot take off from said treadmill IF the wheels are spinning at the same speed so as to cover the exact same distance as the treadmill (ie wheels spinning at 200mph, treadmill moving 200 mph opposite direction) because if that were the case then the plane would actually NOT be moving (meaning it would be generating only enough thrust to overcome the friction in the wheel bearings.

everyone is looking at the can it take off and yes, it can but given the conditions specified by Mountaineer, no, it cannot.

We don't need any other explanation than this. This is EXACTLY what is going to happen.Its just that the thrust needed to overcome the friction and equal the speed of the treadmill is so little. And if it is just overcomming friction and at the same speed as the treadmill then NO it will not take off. NO MATTER HOW FAST THE TREADMILL IS GOING IT WILL TAKE THE SAME AMOUNT OF THRUST TO GET THE WHEELS AT AN EQUAL SPEED TO THE TREADMILL.

[scuba91ta]

Guys, the engines on the plane apply thrust TO THE FRAME OF THE PLANE, by using the propelled exhaust!! the wheels turning are not going to stop the plane from moving, it's merely going to turn the wheels at 2x there normal speed because the engines are going to propel the plane forward, thus allowing the wings to achieve lift...

the wheels and the ground moving under the plane makes no difference!

[Mainerunr]

Originally Posted by scuba91ta

Guys, the engines on the plane apply thrust TO THE FRAME OF THE PLANE, by using the propelled exhaust!! the wheels turning are not going to stop the plane from moving, it's merely going to turn the wheels at 2x there normal speed because the engines are going to propel the plane forward, thus allowing the wings to achieve lift...

the wheels and the ground moving under the plane makes no difference!

correct except that if the wheels and treadmill are moving at the same velocity, opposite direction, then the plane is stationary with respect to the air and thus cannot take off.

[westexasrepublic]

So your saying that if the treadmill was going the direction of the plane taking off that it will take off 2x as fast!? WOW! why have we not installed treadmills on aircraft carriers! dumb US government! or just silly CF members with silly theorys.



edit: sorry im not trying to attack anyone, that was rude, Also personal sorry to mountaineer.> cont disc.

Originally Posted by Mountaineer

The way I read the problem online was that the wheels and the treadmill are going the same speed. Yes, if the treadmill is long enough and the plane was going faster than the treadmill, it will take off, that's simple.