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Post by lumpy on Jan 9, 2008 15:04:24 GMT -5
This is a really stupid debate. Morbidely obese and out of shape aircraft disagree.  |
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Post by Mod (PQ-Kermie) on Jan 9, 2008 15:30:44 GMT -5
Wait wait wait... just hollllllld up. I got a question.... If there is a tree in the plane.. the plane is remote controlled.. and uses auto pilot. Upon takeoff if the tree falls inside the plane... does anybody hear it??
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Post by rocko on Jan 9, 2008 15:35:36 GMT -5
If I put regular coke into a diet coke bottle, does it void out the calories?
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zeke
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Post by zeke on Jan 9, 2008 15:40:01 GMT -5
Well, the whole tree falling dealio might be an interesting debate...unless we required a definition of sound, up front.
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Post by goods on Jan 9, 2008 15:54:34 GMT -5
The part that is hurting my head is... where the treadmill runway matches the speed of the wheels. I understand the prop/jet is propelling the plane, not the wheels.... but it still hurts my head.
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zeke
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Post by zeke on Jan 9, 2008 16:19:27 GMT -5
The part that is hurting my head is... where the treadmill runway matches the speed of the wheels. I understand the prop/jet is propelling the plane, not the wheels.... but it still hurts my head. The speed of the wheels is only indicative of the lateral speed of the aircraft over the fixed runway. With enough thrust, the fuselage could be propelled down the runway on it's belly. Even then, if the runway were a treadmill and it matched the velocity that would be achieved by the engine thrust, from our perspective beside the aircraft, it would be stationary, just like Steve on his treadmill, and there it would remain as stationary airfoils do not usually generate lift. Severe weather is one exception, however. |
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Post by lqdKaos on Jan 9, 2008 16:41:22 GMT -5
This is a really stupid debate. The aircraft must be moving laterally through an air mass in order to produce lift. When you are running on a treadmill, do you run into the far wall? No? Why not? You don't because the lateral movement is a result of an imbalance of forces acting on the aircraft. The thrust of the engines overcome the static drag and friction of the wheels over the runway, forcing the aircraft to roll forward, down the runway, but more importantly, through the air mass. Now, if the runway were to match the force applied via the engines, like a treadmill, the forces would remain in balance and the aircraft would not roll, just as you don't move laterally through your bedroom when you are playing hamster on your treadmill. The treadmill absorbs the thrust applied. For an experiment, turn on your treadmill as fast you can and still stay on it. How much wind is in your face? You have provided an argument against your own statement. 1) The jet's engine produces forward movement by forcing air and producing thrust independent of the aircraft's wheels. Thereby pushing the aircraft thru the air. 2) If you place a car on a treadmill, the engine produces forward movement by transferring torque to the wheels there by pushing the car forward, but movement depends on the wheels to produce forward movement. 3) If you run on a treadmill, you are using power generated by moving your feet on a surface. It is the physical movement of your feet pushing off the ground that produces physical movement. 3 scenarios 1) Jet engine pushes forward using air. Much like a balloon. 2) Car pushes forward using force against the ground 3) Person moves forward using force against the ground. The Jet is the only one that can move without transfering power to the ground. Since forward movement using air is independent of the ground, a jet on a giant conveyor will take off. Even if the conveyor matches and even exceeds the speed of the aircraft's spinning wheels. Try this experiment. Get on a treadmill with an inflated balloon. Run as fast as you can. Release the balloon. Does it move forward and take off? Yes, because it is not dependent on transfer of power to the ground for movement. |
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zeke
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Post by zeke on Jan 9, 2008 16:51:31 GMT -5
For an experiment, turn on your treadmill as fast you can and still stay on it. How much wind is in your face? You have provided an argument against your own statement. 1) The jet's engine produces forward movement by forcing air and producing thrust independent of the aircraft's wheels. Thereby pushing the aircraft thru the air. 2) If you place a car on a treadmill, the engine produces forward movement by transferring torque to the wheels there by pushing the car forward, but movement depends on the wheels to produce forward movement. 3) If you run on a treadmill, you are using power generated by moving your feet on a surface. It is the physical movement of your feet pushing off the ground that produces physical movement. 3 scenarios 1) Jet engine pushes forward using air. Much like a balloon. 2) Car pushes forward using force against the ground 3) Person moves forward using force against the ground. The Jet is the only one that can move without transfering power to the ground. Since forward movement using air is independent of the ground, a jet on a giant conveyor will take off. Even if the conveyor matches and even exceeds the speed of the aircraft's spinning wheels. Try this experiment. Get on a treadmill with an inflated balloon. Run as fast as you can. Release the balloon. Does it move forward and take off? Yes, because it is not dependent on transfer of power to the ground for movement. Sorry, you are still wrong. The friction of the wheels staying in place, or the belly of the aircraft dragging along the runway in the absence of wheels, still must be overcome. In the example of the treadmill, that same friction, which must be overcome or the aircraft would not move an inch, will increase with the speed of the treadmill. As long as they are in balance, no amount of thrust will move the aircraft. There is no free lunch in physics. |
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Post by lqdKaos on Jan 9, 2008 17:20:10 GMT -5
I love this question  Take this for example, At the equator, the circumference of the Earth is 40,070 kilometers, and the day is 24 hours long so the speed is 1670 kilometers/hour ( 1070 miles/hr). The earth rotates from west to east. So, the earth is rotating from west to east at a speed of a little over 1000 mph. If your argument were true, an aircraft would never be able to take off heading west. |
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Post by goods on Jan 9, 2008 17:24:14 GMT -5
aren't we all moving at the same speed as the Earth....
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zeke
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Post by zeke on Jan 9, 2008 17:27:02 GMT -5
Of course, the problem with this, uhm, type of theoretical problem is one of assumptions.
The most accepted answer is that "of course it will take off", but this requires assumptions regarding the friction and efficiency of the bearings and the argument against infinite friction being imparted by the "theoretical" treadmill.
Given the simple wording, it is really not possible to resolve.
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zeke
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Post by zeke on Jan 9, 2008 17:30:01 GMT -5
I love this question Take this for example, At the equator, the circumference of the Earth is 40,070 kilometers, and the day is 24 hours long so the speed is 1670 kilometers/hour ( 1070 miles/hr). The earth rotates from west to east. So, the earth is rotating from west to east at a speed of a little over 1000 mph. If your argument were true, an aircraft would never be able to take off heading west. A red herring. Of course, the airplane sitting on the tarmac at Equatorial International is also traveling at 670 kilometers/hour ( 1070 miles/hr. |
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Post by lqdKaos on Jan 9, 2008 17:31:03 GMT -5
aren't we all moving at the same speed as the Earth.... Thats my point. If the aircraft could not take off on a treadmill that matches the rotational speed of the tires, then the aircraft could never take off going west, for in order to do so, the aircraft would have to overcome the speed of the earth's rotation. |
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Post by lumpy on Jan 9, 2008 17:32:13 GMT -5
I love this question Take this for example, At the equator, the circumference of the Earth is 40,070 kilometers, and the day is 24 hours long so the speed is 1670 kilometers/hour ( 1070 miles/hr). The earth rotates from west to east. So, the earth is rotating from west to east at a speed of a little over 1000 mph. If your argument were true, an aircraft would never be able to take off heading west.  |
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Post by wizer on Jan 9, 2008 17:32:58 GMT -5
It also must be assumed that the extreme heat generated by the friction of the wheels against the treadmill wont blow the tires and melt the landing gear resulting in a crash.
I understand zeke's points, about how the friction between the wheels of the plane and the treadmill must be dealt with, and in reality "given the simple wording it is impossible to resolve the problem".
Interestingly enough, this problem is going to be addressed on Myth Busters on January 30th, using a scale model as well as a full sized plane. While not exactly the "ideal situation" described in this problem, it is certain they will have a full explanation for this concept.
Stay tuned!
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