Discussion
What is it with the latest spat of hypothetical physics questions being posed, which get answered correctly by numerous qualified, experienced, and educated people, only for a select few "confused" posters to swear blind that they are correct despite overwhelming proof and explanations to the contrary?
How on earth do these people get through life refusing to believe others who clearly have considerably greater knowledge and understanding about something than they do, and then have the audacity to say that those in the know are talking rubbish?
I presume that the next time one of these folk get on a plane they'll be able to tell the pilot how to take off without using the engines because they know where to find a giant wind tunnel and moving runway where the laws of physics don't apply
How on earth do these people get through life refusing to believe others who clearly have considerably greater knowledge and understanding about something than they do, and then have the audacity to say that those in the know are talking rubbish?
I presume that the next time one of these folk get on a plane they'll be able to tell the pilot how to take off without using the engines because they know where to find a giant wind tunnel and moving runway where the laws of physics don't apply
Jay GTI said:
Is it really that important? Is your life really that affected by some random posting on an internet forum? Of course if we were all as wonderful as you lot, there wouldn't be a problem right?
Christ, I always thought PH was full of snobs but this thread takes the biscuit...
It isn't important and it doesn't effect my life any more than it does yours. Inside the example I gave, the crux of what I was asking is why some people argue the toss even after overwhelming evidence/explanations to the contrary.
I don't really see how that could be regarded as snobby.
orgasmicliving!! said:
stuff
It's affect, not effect, the way you have used it and there's no such word as snobby. Did you mean snobery?
>> Edited by orgasmicliving!! on Friday 26th May 16:34
Would you care to answer my original question or would you prefer to go off on a petit nitpicking tangent?
You do after all have an excellent insight into what I’m taking about. You contribution will be most welcome.
FFS....just apply the laws of conservation of energy and all will become clear. Energy cannot be created or destroyed, only converted from one form to another.
If you believe that the energy from the engines is going into accelerating the angular velocity of the wheels; please explain how this energy transfer mechanism works.
So far my original question still stands......
If you believe that the energy from the engines is going into accelerating the angular velocity of the wheels; please explain how this energy transfer mechanism works.
So far my original question still stands......
allnighter said:
FFS....just apply the laws of conservation of energy and all will become clear. Energy cannot be created or destroyed, only converted from one form to another.
If you believe that the energy from the engines is going into accelerating the angular velocity of the wheels; please explain how this energy transfer mechanism works.
So far my original question still stands......
Ok I will try and see it from your point of view:
From what I understood so far from you is, the plane uses the jet engines to move forward ie sucks air to move forward, and that is the basic principle of its forward motion, completely detached from the ground or wheels.Ok?, so according to you , if the plane is sucking air to move forward then if you put a conveyor underneath its wheels (which are primarely used to reduce friction with the ground) it shouldn't make a difference to the movement of the plane , the plane will still move forward and fly right?the energy used in the plane is completely detached from the ground, so whatever you try to do on the ground(in relation to the wheels) wont affect the plane , so it will take off.If the plane was a car , then the conveyor belt will affect the car because the car relies solely on the wheels to transfer energy as opposed to the plane relying on propellors or jet engines.
I can see clearly now where you are coming from Dave.
Another scenario would be to put a float plane in a fast flowing river and try to fly it going upstream , I guess the plane will take off anyway as the river underneath is acting just like a conveyor belt/wheeled plane scenario and would not stop the plane going upstream and take off eventually.
How am I doing so far?
In conclusion, am I right in saying that the only way to stop the plane moving forward is to stick a giant fan in front of it to act the same way as a conveyor belt in a car/conveyor belt scenario?
Excellent!!!!
Finally someone has seen the light. Apply this law to any of the situations mentioned and you'll see that they are either possible or impossible. The energy has to be accounted for.
p.s. I like your 635 CSI....tres cool
>> Edited by dvs_dave on Sunday 28th May 08:10
ATG said:
FFS....just apply the laws of conservation of energy and all will become clear. Energy cannot be created or destroyed, only converted from one form to another.
If you believe that the energy from the engines is going into accelerating the angular velocity of the wheels; please explain how this energy transfer mechanism works.
So far my original question still stands......
Ok I will try and see it from your point of view:
From what I understood so far from you is, the plane uses the jet engines to move forward ie sucks air to move forward, and that is the basic principle of its forward motion, completely detached from the ground or wheels.Ok?, so according to you , if the plane is sucking air to move forward then if you put a conveyor underneath its wheels (which are primarely used to reduce friction with the ground) it shouldn't make a difference to the movement of the plane , the plane will still move forward and fly right?the energy used in the plane is completely detached from the ground, so whatever you try to do on the ground(in relation to the wheels) wont affect the plane , so it will take off.If the plane was a car , then the conveyor belt will affect the car because the car relies solely on the wheels to transfer energy as opposed to the plane relying on propellors or jet engines.
I can see clearly now where you are coming from Dave.
Another scenario would be to put a float plane in a fast flowing river and try to fly it going upstream , I guess the plane will take off anyway as the river underneath is acting just like a conveyor belt/wheeled plane scenario and would not stop the plane going upstream and take off eventually.
How am I doing so far?
In conclusion, am I right in saying that the only way to stop the plane moving forward is to stick a giant fan in front of it to act the same way as a conveyor belt in a car/conveyor belt scenario?
Excellent!!!!
p.s. I like your 635 CSI....tres cool
>> Edited by dvs_dave on Sunday 28th May 08:10
There's only one tiny fly in the ointment ... you can't arbitrarily split the plane and its engines into a separate system from the wheels and the conveyor. That is just plain wrong. They are connected and there are inevitably forces transferred between them, unless the wheels have no mass. Are these forces significant? That depends on a bunch of parameters that aren't specified in the question. By all means say that the forces aren't siginificant, but you can't say they are zero.
If you don't believe energy from the engines goes into the angular velocity of the wheels (in your words) ... would you care to explain where the energy comes from to spin the wheels of an aircraft taking off on a conventional runway?
The engines can only transfer energy (in the form of kinetic energy) into the wheels if it moves them. This is obvious from the KE=1/2 MVsq formula. If V=0, KE=0
In this scenario it was said that the plane doesn't move because the belt linear velocity exactly matches the wheel centripetal velocity. Aside from the obvious fact that this situation is a paradox.....it is also shown to be impossible through the laws of conservation of energy.
Incidentally, when tackling theoretical situations like this, you have to split systems up to determine how they behave. You then re-combine them once the behavior of each has been determined to work out the behavior of the system as a whole. If people were able to think theroetically properly and not get tangled up with bringing in irrelevant, undetermined and negligable "real world" parameters all would become clear.
Go back and have another think about it.......
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