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Airplane on a Conveyor Belt - Mythbusters Tonight!


LPFSTheFett

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What if the wheels are taken out of the equation? Imagine square blocks instead of the wheels. This rules out MY thoughts on the treadmill, in essence.

 

Will the plane still take off? If so, why?

 

KillJoy

Last time I checked they don't make airplane with square wheels. :cool:

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The prop pulls the plane...... true

 

The wheel roll on the ground..... true

 

The prop pulls the plane, and the plane's wheels roll on the ground.

 

If the ground moves at an equal speed of the wheels, for the plane to be stationary, it WILL NOT FLY. Just like a person on a treadmill. Why do you not run into the Wall? The treadmill is moving at the same speed you are, and you stay stationary.

 

KillJoy

As I said in my last post: This is not a problem similar to a person walking on a treadmill, because the wheels on the plane don't provide the forward motion, thrust from the engines does.

 

Picture yourself in a pool, swimming laps. Your arms paddle through the water the same way the propeller pulls the plane forward. If you put a treadmill on the bottom of the pool (and turned it up to the speed you were swimming) would you stop moving through the pool? Even if you had wheels attached to your body that were riding on the treadmill? The answer is no.

 

Now, could you put the plane on the treadmill, turn the treadmill up to 25 mph, and slowly increase the engine speed so that the plane didn't move? Well, yes. But the plane would barely be making any thrust and wouldn't be able to take off even if it weren't on the treadmill. (It would be like driving an automatic transmission car and taking your foot off the brake. The engine isn't making much power, but you roll) But the experiment was whether the plane would be able to take off normally if it was on a treadmill, and for that the answer is yes.

 

Anyone who has taken high school physics should be able to draw a free-body diagram showing opposing forces. If you do that, the answer will be very clear.

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Last time I checked they don't make airplane with square wheels. :cool:

 

I know.... wasn't this a hypothetical scenario to begin with?

 

My point was this..... if the plane physically does not move forward, engines going full speed, there is no lift being generated my the wings, hence NO TAKE OFF.

 

IF the plane moves forward, and enought lift is produced by the wings to counter the weight, and gravity, then yes... it will fly.

 

KillJoy

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The infinitely fast treadmill someone spoke of wouldn't even matter. In your hypothetical world, a treadmill can go infinitely fast. In that same hypothetical world, the wheels would be able to go infinitely fast without creating undue friction from the bearings.

 

Steve, you don't seem to be understanding things. The wheels don't affect the forward motion of the plane at all. If the plane was powerful enough, it would take off with square wheels, it would simply drag them.

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Who actually thought the plane wouldn't take off, really...? :rolleyes:

 

Thrust from the engine and air over the wings (which creates the lift required to take off) has NOTHING to do with the treadmill.

 

 

 

 

 

Here we go again....

http://www.deepstageperformance.com/pics/helicopter-turntable.jpg

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OK OK OK, I stand corrected. My boss here at work just explained it to me. Yes, I'm slow. LoL!! For those who don't understand, think about it this way. Sit the plane up on jackstands. Will it take off? Of course, because the prop is pulling the air to move the plane forward. Whether you have a treadmill going the opposite direction at 200mph or not, the plane will still move forward because it's pulling air.

 

You can also think about how fan boats work. The fan in the back pushes air to move the boat forward. If a fan boat's top speed is 60mph and it's driving against a current that is going 60mph, how fast will the boat be physically moving? Answer: 60mph. The boat is not going to stand still because it is pushing against the air, not the water.

 

Maybe this will help to clear up the confusion...or add to it. Who knows.

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It looked like it took of pretty normal to me....

 

How exactly did it NOT take off normally...? :wtf:

Oops, that was a typo. If you see the explanation in the rest of my post you'll see what I was trying to say. I corrected the typo. I honestly think the swimming pool analogy I made is very easy to understand. I don't know why everyone thinks this is so complicated.

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Oops, that was a typo. If you see the explanation in the rest of my post you'll see what I was trying to say. I corrected the typo. I honestly think the swimming pool analogy I made is very easy to understand. I don't know why everyone thinks this is so complicated.

 

:cool:

 

Reading your post, I was about to say... ;)

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All these big explanations, and the ones who can't figure it out simply can't distinguish ground speed from air speed.

 

The plane needs air speed to take off, not ground. Thats all the more answer is ever needed, if you can't get that, I don't know how you've made it this far.

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