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#301
11-23-2005, 04:41 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ QUOTE ] [ QUOTE ] [ QUOTE ] Patrick, you understand that if the conveyor is going 293476943769437694376mph then the plane has to go 293476943769437694376 + 1 mph to move forward? [/ QUOTE ] The plane doesn't - the wheels' tangential velocity does, but that has absolutely no effect on the forward motion of the plane - the bearings are frictionless - no force gets through to the plane itself. [/ QUOTE ] Finally we admit that the wheels must be going faster than the conveyor, hence the OP conditions are NOT satisfied. [/ QUOTE ] sure they are - the conveyor velocity simply accelerates instantaneously with the wheel's tangential velocity. but as Patrick said, these accelerations have absolutely nothing to do with the forward acceleration of the plane. [/ QUOTE ] Eh - technically then the speed of the conveyor instantly reaches infinity and the wheels infinity+1. Paradox!!! So the whole thing is in fact semantical. 
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#302
11-23-2005, 04:42 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ QUOTE ] [ QUOTE ] [ QUOTE ] How can a CPA understand this (thanks to Patrick [img]/images/graemlins/smile.gif[/img] ) and engineering types can't [img]/images/graemlins/confused.gif[/img] [/ QUOTE ] to be fair, these guys really aren't "engineering types" i think the "physics types" have an edge over the "engineering types", although patrick is sort of both. [/ QUOTE ] the physics types assume the bearings are frictionless, whereas the engineering types live in the real world and account for these types of things [img]/images/graemlins/tongue.gif[/img] [/ QUOTE ] You can't back your way out of this one. Quit trying to pretend like you can't imagine frictionless bearings when you've already accepted a runway flying by at 29674967497694376mph. You were completely wrong and it wasn't because you didn't accept perfect bearings. The only difference non-perfect bearings makes is that the engines would have to be strong enough to overcome whatever insiginificantly small effect the bearing friction would have. You could mount an engine on there that's strong enough to take off if you had the brakes on fully, let alone a little bit of bearing friction. [/ QUOTE ] I'm pretty sure this man owes Soiler $400.
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#303
11-23-2005, 04:42 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ QUOTE ] [ QUOTE ] [ QUOTE ] thats the whole point of a treadmill, so you can run WITHOUT MOVING. [/ QUOTE ] Now throw rollerskates on and use the handles to pull yourself forward. [/ QUOTE ] I'm going to expand on this a little. Imagine you're on the treadmill, on roller skates with perfect bearings. Someone is controlling the speed of the treadmill for you, and they keep turning it up. Since you're on frictionless wheels, the speed of the treadmill doesn't affect you, right? Okay, grab hold of the handles now. Imagine that the dude keeps cranking up the speed on the treadmill. Is there any speed he could possibly turn it up to that could stop you from simply pulling yourself forward with the handles if you wanted to? [/ QUOTE ] people are going to say "but when you pull yourself forward, the wheels will be going faster than the treadmill" which is partially true [/ QUOTE ] They'd be wrong. The wheel center is moving at a different speed, but the surface in contact with the treadmill is not, assuming non-slip conditions (which we are). Do I have to draw a picture of this too, when I unleash my fury?
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#304
11-23-2005, 04:44 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
when I unleash my fury? [/ QUOTE ] after reading all these damned replies, this fury you plan on unleashing needs to be damned impressive.
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#305
11-23-2005, 04:44 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
sure they are - the conveyor velocity simply accelerates instantaneously with the wheel's tangential velocity. but as Patrick said, these accelerations have absolutely nothing to do with the forward acceleration of the plane. [/ QUOTE ] But if there is any tangential velocity of the wheel with respect to the conveyor belt, doesn't that mean that they are operating at different speeds?
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#306
11-23-2005, 04:45 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
fair enough pat, when me and NLsoldier started arguing about this 2 hours ago, his arguement was that the plane is standing still via the treadmill mechanism, it could take off.....this is obviously untrue, and he owes me $400
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#307
11-23-2005, 04:46 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ QUOTE ] [ QUOTE ] [ QUOTE ] [ QUOTE ] thats the whole point of a treadmill, so you can run WITHOUT MOVING. [/ QUOTE ] Now throw rollerskates on and use the handles to pull yourself forward. [/ QUOTE ] I'm going to expand on this a little. Imagine you're on the treadmill, on roller skates with perfect bearings. Someone is controlling the speed of the treadmill for you, and they keep turning it up. Since you're on frictionless wheels, the speed of the treadmill doesn't affect you, right? Okay, grab hold of the handles now. Imagine that the dude keeps cranking up the speed on the treadmill. Is there any speed he could possibly turn it up to that could stop you from simply pulling yourself forward with the handles if you wanted to? [/ QUOTE ] people are going to say "but when you pull yourself forward, the wheels will be going faster than the treadmill" which is partially true [/ QUOTE ] They'd be wrong. The wheel center is moving at a different speed, but the surface in contact with the treadmill is not, assuming non-slip conditions (which we are). Do I have to draw a picture of this too, when I unleash my fury? [/ QUOTE ] YOu're just flat out wrong here. If the plane is moving then the wheel rotational speed must be different than the runway linear speed. If you can't understand that then we have a problem. Imagine teh runway linear speed is moving, and that we have frictionless wheels. Explain to me how the plane could move forward while the wheel rotational speed is 0.
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#308
11-23-2005, 04:46 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
Do I have to draw a picture of this too, when I unleash my fury? [/ QUOTE ] This is an absolute must. Oh man, I can't wait.
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#309
11-23-2005, 04:46 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
I'm going to agree with goofball. According to the phrasing of the OP, the plane is not moving. It's not that the plane is stationary because the plane is like a car and thrust by its wheels, nor because it's physically impossible for the plane to move relative to the ground/air when on a conveyor belt, but rather, the plane is stationary because that's how the problem has been defined. If the plane moves forward any amount relative to the ground such that lifting off would become possible, the criteria laid out in the OP (wheels movement = conveyor movement) is no longer met.
This is not about aerospace engineering, rather so much as it is about reading comprehension (or more precisely, poor phrasing in the original post).
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#310
11-23-2005, 04:47 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
fair enough pat, when me and NLsoldier started arguing about this 2 hours ago, his arguement was is the plane was standing still via the treadmill mechanism, it could take off.....this is obviously untrue, and he owes me $400 [/ QUOTE ] no my argument was that after reading the OP, the plane could take off. I didnt pretend to know exactly how or why. edit-and by OP i mean what has now been defined as the problem (no friction, etc) if you wanna go by the semantics of the OP then i dunno.
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