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#272
11-23-2005, 04:22 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 ] And, as stated in the original problem, the treadmill will speed up to compensate. Thus you dont move. [/ QUOTE ] Alright, now explain to me how the conveyor transmits any sort of force on the CG of the plane when the bearings are perfect bearings. You could have this thing going 293476943769437694376mph and the wheels will spin to match that, but with perfect bearings, nothing gets through to the body of the plane. Now what's counteracting the thrust? Now, do you understand F=ma? Seriously... draw an FBD and it's all pretty easy. [/ 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. 
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#273
11-23-2005, 04:23 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
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]
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#274
11-23-2005, 04:23 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 ] And, as stated in the original problem, the treadmill will speed up to compensate. Thus you dont move. [/ QUOTE ] Alright, now explain to me how the conveyor transmits any sort of force on the CG of the plane when the bearings are perfect bearings. You could have this thing going 293476943769437694376mph and the wheels will spin to match that, but with perfect bearings, nothing gets through to the body of the plane. Now what's counteracting the thrust? Now, do you understand F=ma? Seriously... draw an FBD and it's all pretty easy. [/ QUOTE ] Patrick, you understand that if the conveyor is going 293476943769437694376mph then the plane has to go 293476943769437694376 + 1 mph to move forward? [/ QUOTE ] i'm now convinced this is a troll
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#275
11-23-2005, 04:23 PM
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Re: think about this...
What actually happens to the wheels here? Would there be skidding as the plane moves forward, the wheels turn faster and the treadmill adjusts accordingly?
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#276
11-23-2005, 04:24 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ QUOTE ] The thing is, as stated in the original problem, the runway speeds up to compensate for the extra +x force. [/ QUOTE ] But that's the issue here, CAN the runway compensate for the thrust of the engines? Imagine the wheels are frictionless, and the conveyor belt is spinning backwards at 100 mph and the plane is just sitting there, engines at idle. The conveyor belt has no effect on the plane and therefore has no way to counteract the thrust of the plane. [/ QUOTE ] Yes but in that situation, for the air speed to be > 0, the speed of the wheels has to be > 100. The plane will take off, but the wheels and conveyor will not be going the same speed, therefor the conditions of the OP will not have been met. I'm still waiting for someone to explain where I'm wrong.
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#277
11-23-2005, 04:24 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
Jesus christ. If the wheel rotational speed is free to be faster than the speed of the conveyor runway then the plan can take off. The speed of the conveyor runway could be the 1M m/s and the plane would still take off.
However, as I understand the OP questoin, by definition the wheel rotational speed is must be the same as the speed of the conveyor runway. If that's the case then how can the plane take off?
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#278
11-23-2005, 04:25 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ 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.
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#279
11-23-2005, 04:25 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ 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 ] Because the CPA listens to Patrick and sometimes the "engineering types" aren't really engineers at all so much as they're just enrolled in the classes. Okay, for real now - I'm out.
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#280
11-23-2005, 04:26 PM
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Re: Physics graduate from Daryn\'s alma mater\'s answer
[ QUOTE ]
[ 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 ] And, as stated in the original problem, the treadmill will speed up to compensate. Thus you dont move. [/ QUOTE ] Alright, now explain to me how the conveyor transmits any sort of force on the CG of the plane when the bearings are perfect bearings. You could have this thing going 293476943769437694376mph and the wheels will spin to match that, but with perfect bearings, nothing gets through to the body of the plane. Now what's counteracting the thrust? Now, do you understand F=ma? Seriously... draw an FBD and it's all pretty easy. [/ 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 bearings are frictionless - no force gets through to the plane itself. [/ QUOTE ] who said the plane has perfect bearings?
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