re: Myth Busters/Can a plane take off on a conveyor belt

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That's 2 external forces in the skating example. The handrail and the rope.
In the plane example, the only external force is the engine and it is being reversed by the treadmill.

BOOM!!!

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you don't need a handrail and a rope on a treadmill. just the handrails.

you would pull yourself forward with either though.

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you don't need a handrail and a rope on a treadmill. just the handrails.

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Not if you just held onto the handrails. You'd stay still.

Ok, let me try to get this straight in my head. You're in a plane and you're giving it enough gas to go 100 mph. The treadmill is going 100 mph in the opposite direction. Is this the crux?

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it's not like a treadmill. a person on a treadmill is propelling themselves forward by pushing off of the ground.

think of it like this.
there's a long treadmill. there are hand rails on either side of it. you stand in the center of the conveyor belt on roller skates. you take your hands far out and front of you and pull Yourself forward. the treadmill goes in the opposite direction at that same amount of force.

You would still move forward. Your arms pulled you forward (with relation to your initial position) and are in facting holding you at your new postion on the treadmill. your wheels would still be spinning underneath you but your arms are keeping you in your place.

Your arms and the rails= the jets and the air.

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You're absolutely right, but I didn't say the plane wouldn't move forward, I said it wouldn't take off and it won't. But if all you're trying to do is move the plane forward, all you have to do is increase the thrust to counteract the speed of the treadmill, this is addition and subtraction, doesn't take a fricking mythbuster to answer this. The question is will it take off, since thrust and horizontal speed do not provide lift, the answer is no. I really don't understand why this is so hard to understand. Do you guys not know the basic physics of flight. You guys keep arguing about the speed of the conveyer belt etc, when they don't mean anything, they are simply there to make the plane immobile to the surrounding air while in full thrust. Think of it this way, the plane is chained from the rear so it can not move forward, relative to the air, i keep saying this phrase, because its the most important factor of them all, so it's chained from the rear and it is on full power thrust, will it just levitate straight up? Your theories would say yes. But the answer would be a resounding NO.

Or regardless of whether or not you were on a still or moving surface...

How can this thread still be going?

Airspeed over wings makes a plane "take off." Nothing else.

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Right but then the force moving forward would be greater than the force moving backwards. It'd be like giving enough gas to go 200 mph and only 100 mph of treadmill speed.

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Okay, then look at the pulling along a rope example. Say you pull yourself along a rope (on skates) and time it to be 5 mph. Then, you do the same thing while on a treadmill going 5 mph the opposite direction... you'd still be pulling yourself along (and moving) at 5 mph, but the skates would be spinning at 10 mph instead of just 5.

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You're absolutely right, but I didn't say the plane wouldn't move forward, I said it wouldn't take off and it won't. But if all you're trying to do is move the plane forward, all you have to do is increase the thrust to counteract the speed of the treadmill, this is addition and subtraction, doesn't take a fricking mythbuster to answer this. The question is will it take off, since thrust and horizontal speed do not provide lift, the answer is no. I really don't understand why this is so hard to understand. Do you guys not know the basic physics of flight. You guys keep arguing about the speed of the conveyer belt etc, when they don't mean anything, they are simply there to make the plane immobile to the surrounding air while in full thrust. Think of it this way, the plane is chained from the rear so it can not move forward, relative to the air, i keep saying this phrase, because its the most important factor of them all, so it's chained from the rear and it is on full power thrust, will it just levitate straight up? Your theories would say yes. But the answer would be a resounding NO.

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the point is though guy, is that if the plane can move forward, it has rendered the conveyor belt moot.

it will move forward in relation to it's beginning point at almost the same speed as normal. Thus causing air to flow over the wings, and the plane to be able to achieve enough speed to lift.

In the same way. if you were pulling yourself forward on that treadmill, would you not feel the air resistance on your face?

right.

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End all of your posts with that from now on.

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Seriously thinking about it.


ETA: BOOM!!

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Right but then the force moving forward would be greater than the force moving backwards. It'd be like giving enough gas to go 200 mph and only 100 mph of treadmill speed.

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For the 80,000,000th time, wheel speed has NOTHING to do with if a plane can take off or not, air/wind speed against its wings does.

What does the treadmill have to do with airspeed? NOTHING.

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the point is though guy, is that if the plane can move forward, it has rendered the conveyor belt moot.

it will move forward in relation to it's beginning point at almost the same speed as normal. Thus causing air to flow over the wings, and the plane to be able to achieve enough speed to lift.

In the same way. if you were pulling yourself forward on that treadmill, would you not feel the air resistance on your face?

right.

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I understand this, so you think the point of the test is can a planes thrust overtake the speed of the conveyer belt. I don't think thats the point of it. I think its meant to see if the plane takes off in relation to the air around it.