This sounds like you are saying the conveyor is moving in the same direction as the rotation of the wheels (or what the rotation of the wheels would be), not the opposite direction.
Plane moves forward 5mph. Conveyor matches 5mph (which also zeroes wheel rotation) Plane stops conveyor continues. Now the wheels are spinning backwards at 5mph. Would that not be opposite direction of rotation? Seems to me if that was the same direction of rotation it would accelerate or spin the tires in a forward direction.
Okay, I got you. I can see how the question could be interpreted that way. I think the OP meant to say that the conveyor is moving in the opposite direction that the plane is pointed. Or in the opposite direction of what the plane intends to take off to. Some ambiguity there.
I think when we are talking about a question designed to confuse (12 years and 2500+posts!) it's important to arrive at a solution based on what's written rather than make assumptions about intent. It specifically states "moving in the opposite direction of rotation" but does not state opposite direction of the aircraft. I believe my proposed solution meets all criteria as written.
I think you always have to consider intent, and also the context of the question. In this case we are talking about a plane which "intends to take off". So to consider the term "direction of rotation" to mean the forward motion of the wheels of a plane trying to take off is a reasonable inference.
Not in the least. It's a clearly written question that just as easily could have said "direction of aircraft" instead of "direction of rotation". I consider "opposite direction of rotation" to mean "opposite direction of rotation". If you want to change the meaning as written to suit your idea of what the question was supposed to mean but doesn't actually say we will have to agree to disagree.
I think it is safe to say the original question (which went, to use that term I hate 'viral') was simply meant to confuse an airplane with a car in that how the energy transmitted or converted, is used to move the object. The wording used in this example was almost incidental and not intended I believe. I voted 'yes' to take off because that is how I saw the question and how it was elsewhere (other car forums) it was only when it was pointed out the the question could be interpreted in a way that constrained the take-off. However I agree with what James said in the the opposite direction of rotation would cause the wheels to slip and that in fact the conveyor as such is moving in the same direction as the aircraft and indeed not the opposite as was actually intended.
Alan, I've been flying for over fifty years as a commercial pilot, but I could have answered this question even before I obtained my license. The answer to the question is a resounding NO! Lift depends on "relative wind", the speed of the air flowing over and under the wings, especially over. An extreme example of this would be a plane tethered to the ground by a long rope (with a pilot at the controls, of course). If it were facing into the wind, and the wind was blowing at, say, 70 mph or anything above the stalling speed (i.e. the speed at which air can no longer flow smoothly over the top surface of the wing) of that particular airfoil, the plane could lift off the ground and effectively be flown as a kite, remaining above the spot on the earth where it sat before the wind began to blow. If, on the other hand, that same plane were facing backwards while riding on a trailer truck traveling downwind at the exact 70 mph that the wind were blowing, it would be traveling with the airmass and the relative wind would be zero mph. Obviously, it would not be able to fly under those conditions. Likewise, if the plane were stationary relative to the ground (not relative to the moving belt you stipulate), it could not fly unless the wind were blowing at a velocity above the wing's stall speed (see above description of plane flying as a kite). The belt could be moving at 100 mph, but as long as the plane's engine is driving the propeller with enough power for the plane to hold station relative to the ground, it doesn't matter that the plane's wheels are spinning at a tremendous rate, and the rolling resistance of the rubber tires combined with the friction of the wheel bearings are trying (unsuccessfully) to drag the plane backwards, there is still no relative wind, so the plane will never fly under this set of circumstances unless the wind is blowing faster than the stalling speed of the airfoil. If this is clear as mud, it's because I've tried to include all the factors that lead me to the third word in the second line: NO. If you'd like me to work at further clarifying any of my points,please let me know! Happy Thanksgiving, Dave
OK, I got snookered! I misinterpreted the stipulation that the belt moved backward, exactly matching the forward rotation of the plane's wheels. Rather than realizing that this would not prevent the plane from accelerating forward, I took it to mean that it would keep the plane stationary relative to the ground....therefore, I have to concede that the plane WOULD be able to take off. I am currently hunting for a crow to eat, along with my humble pie! Other than that, you'll have to admit that I made some good points. Dave
I can't believe I'm on this again Originally I said it would take off however consider this part of the statement (which I don't believe was intended) The conveyer belt is designed to exactly match the speed of the wheels at any given time This part of the statement sets a parameter and it cannot be broken. The power to take off is indeed provided by the jet or propeller forcing pulling/pushing air and unlike a land vehicle where the power is transmitted through the wheels onto the ground the aircraft still moves forward. However for it to move forward initially the wheels would have to move faster than the belt and the question specifically restricts that action. As the aircraft will not move relative to the ground it can't take off.
If the conveyor matches wheel speed in terms of airspeed you have craft airspeed, wheel airspeed and conveyor airspeed all matching and the plane flying. This matches criteria of conveyor exactly matching wheel speed even if the plane wheel is not rotating (does not specify in relation to what). Impossible to match rotationally (rpm) as a conveyor would have a huge diameter in comparison to the plane tire. In relation to each other and in relation to the rest of the planet equals the conveyor following the plane cancelling out wheel rotation.
To reduce this problem to its simplest form: 1. Because the plane is simply sitting on the belt, with its landing gear free to turn, it doesn't matter whether the belt is moving at fifty miles per hour, or zero miles per hour. The statement that the belt is adjusted to always move at the same rate as the plane's wheels is a red herring, thrown into the mix just to muddy the waters, and it was eminently successful at doing just that. 2. When the plane's throttle is opened to start the takeoff roll, there is nothing to prevent the plane from accelerating, other than the negligible rolling resistance of the tires and wheel bearings, both of which are easily overcome, as they are when any plane accelerates for takeoff, whether the runway surface is turf, gravel, sand, asphalt, concrete, or...a belt. ERGO: The plane will take off. All else ist sturm und drang!
The forward motion of the plane will cause the wheels to be spinning faster than the conveyor. The conveyor will spool up to infinity trying to catch up. Long before it reaches infinity, the tires of the planes wheels will lose traction and skid. With skidding tires, the plane takes off whilst meeting the requirement of matching the spin of the wheels to the speed of the conveyor. Could such a conveyor be constructed ? Certainly not one that would spool up to infinity, but perhaps one that would spool up fast enough to make the tires of the plane lose traction.
As written, the conveyor would match airspeed and zero out wheel speed. In order to accomplish what you describe (which is opposite of how the question is written) it would have to move in the same direction of wheel rotation (therefore accelerating it) while breaking traction only enough to compensate for airspeed. So, airspeed 10mph it would have to break traction by a 10mph difference between the belt and tire. Not enough speed delta to do this when the only resistance it faces is the polar moment of the tire wheel assembly. To accelerate hard enough to break and keep a break in traction the conveyor would be accelerating far faster than the tire, therefore not matching speed in any way.
Then why are they moving the conveyor belt in the opposite direction of the plane taking off in this test ? Or are you telling me that this is a different airplane/conveyor belt question ?
Also, your interpretation of the question is flawed, because a spinning wheel does not indicate a direction, other than the direction that the plane would move.
Your interpretation is flawed. Spinning wheel does in fact determine "direction of rotation". It is defined by nothing else. Not a single thing about the myth busters test that matches the criteria here. Read and try again
If post 2577 doesn't establish "direction of rotation" how does it make sense to you otherwise? Moving opposite -direction of rotation- cancels wheel rotation with airspeed. Or, would spin the wheel backwards if tethered. Moving the same -direction of rotation- would accelerate the wheel in a forward direction.
The direction of a spinning wheel at the bottom of the wheel is the exact opposite of the direction at the top of that wheel. Then we have different directions at the sides of the wheel. A spinning wheel does not define a linear direction, other than the direction of a vehicle attached to it would be moving. Also, the OP states "This is flying all over the net". There is no question that I've seen "flying all over the net", that has the conveyor moving in the same direction as the plane taking off. How would there be any question of the whether the plane would take off under those circumstances anyway ?
Could you show me where the question states "linear direction" because all I see is "direction of rotation". From the right side of the plane, moving forward the wheels spin clockwise. That is direction of rotation. Opposite direction of rotation would zero wheel speed or spin it counter clockwise. Same direction of rotation is of course clockwise or accelerating the tire in the same direction. The question does not state the conveyor moves opposite direction of the aircraft. How would there be a question of whether the plane would take off under those circumstances? There is, in post one. It was designed to confuse as it's done quite well as you have decided it should mean what you think it should mean rather than what it says.
A wheel that is spinning clockwise from your viewpoint will move to your right. The opposite is to the left. I believe that the intent of the OP's question was to suggest that the conveyor was moving in the opposite direction of the plane taking off. And by way of matching the speed of the wheels, prevents it from moving forward. If instead, it is as you suggest, that the conveyor is moving in the same direction as the plane, then this is not the same question that is "flying all over the net", and what the Mythbusters episode was designed to solve. Perhaps the OP could chime in to clarify.
Again, it does not say opposite of movement in relation to the earth or opposite of movement of the aircraft. It clearly says opposite direction of rotation. Clockwise and counterclockwise would define direction of rotation not moving right or left. So to be clear you believe the question was written incorrectly and the OP intended to write it in a different manner? This is not a valid argument. If it was meant to say it moves in the opposite direction of the aircraft why -wasn't- it written as such? Sorry, you can't change around the wording of a problem to suit your solution. It has to be answered as written.
No, you're just not understanding the question properly. The conveyor moves in a linear direction. Let's have the OP clarify exactly what he meant.
Your argument is ridiculous. I understand what "direction of rotation" means and that is what the question states. Doesn't even matter if the OP decided to re-write the question. You would have to delete this entire thread and start over.
