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plane question

#181
theshadow2001 said:
I'm sorry I don't have time right now to read through the ohter forums right now. If you would be so kind to tell me which one of the posts does the explaining I would be happy to read it though. I have no problems with being prooved wrong and I would think it's great to see what the answer really is

Just one more thing. The jet engine is only ever doing enough to keep the plane stationary realtive to the ground. If the plane is stationary it can not take off. If the engines were blowing air on to the wing then it could take off however the engine blows air behind the plane and it's the reaction force of that air that moves the plane forward. That reaction force is only enough to keep the plane at the same speed as the conveyor and thus keeping it stationary

Why does an aircraft carrier need a runway. Why not keep the plane stationary until it's engine is doing enough for it to take off? Because if its not moving it wont take off.

Again apologies for not reading but will come back later and have some humble pie if need be.
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#182
#183
theshadow2001 said:
I'm sorry I don't have time right now to read through the ohter forums right now. If you would be so kind to tell me which one of the posts does the explaining I would be happy to read it though. I have no problems with being prooved wrong and I would think it's great to see what the answer really is

Just one more thing. The jet engine is only ever doing enough to keep the plane stationary realtive to the ground. If the plane is stationary it can not take off. If the engines were blowing air on to the wing then it could take off however the engine blows air behind the plane and it's the reaction force of that air that moves the plane forward. That reaction force is only enough to keep the plane at the same speed as the conveyor and thus keeping it stationary

Why does an aircraft carrier need a runway. Why not keep the plane stationary until it's engine is doing enough for it to take off? Because if its not moving it wont take off.

Again apologies for not reading but will come back later and have some humble pie if need be.
Click to expand...
Just read the links a few post above, the one I posted explains it pretty well, apparently, this is like a joke played on pilots and aircrews in training, and I got fooled too.
 
#185
theshadow2001 said:
Are you talking solely bout the article at the top of this page?
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They're referring to the first article and not the replies. You can also scan back through the thread and read my posts, or a number of other posts. Most people who understood that it will take off also understood why.
 
#190
Bob Lee (QSC) said:
The engines require oxygen in the air to combust the fuel, and the wing requires air flow to create lift, but engine thrust does not work by pushing against air. A jet engine produces thrust because the heat released by combustion drastically expands the gases in the engine, which have nowhere to escape but out the exhaust in the back. So hurtling the mass of hot gases backwards causes an equal and opposite reaction (one of Newton's laws of thermodynamics, but I don't remember which one): the engine pushes forward, exerting a force on the mass of the plane.

When Robert Goddard spoke of one day using rocket propulsion for travel outside of the Earth's atmosphere, he was pooh-poohed by many who thought, wrongly, that even a rocket could not function in a vacuum like outer space because it had no air to "push" against.
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I was going to post something similar, but then I decided not to. In the event that I made myself look stupid. I answered no at first then I remembered... mass goes this way <--- and plane goes that way --->
 
#194
I have a physics/chemistry question for ya'll.

If there was some material which is IMPOSSIBLE to break, and is also a bad insulator. And an hollow sphere of that material is filled up with water completely. Then the sphere is placed in a really cold place...What will happen to the water?

-Will it freeze into ice without expanding?
-Will it get colder than zero but not freeze?
-Will its temperature stay above zero?
 
#195
Jazzin' said:
I have a physics/chemistry question for ya'll.

If there was some material which is IMPOSSIBLE to break, and is also a bad insulator. And an hollow sphere of that material is filled up with water completely. Then the sphere is placed in a really cold place...What will happen to the water?

-Will it freeze into ice without expanding?
-Will it get colder than zero but not freeze?
-Will its temperature stay above zero?
Click to expand...

A phase diagram of water will answer your question. You need more info than that to be able to answer your question. It could be any of your first two suggestions, but not the last one. The increasing pressure as the ice forms will reduce the freezing point of the water, but it depends how cold we are talking... just below zero, absolute zero or anywhere in between. Ahh second year chemistry, how I hate you.

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#197
Jazzin' said:
I have a physics/chemistry question for ya'll.

If there was some material which is IMPOSSIBLE to break, and is also a bad insulator. And an hollow sphere of that material is filled up with water completely. Then the sphere is placed in a really cold place...What will happen to the water?

-Will it freeze into ice without expanding?
-Will it get colder than zero but not freeze?
-Will its temperature stay above zero?
Click to expand...

Why can it not freeze AND expand?

just because the material is unbreakable doesn't mean it cannot be stretched out as the ice expands.:D

On the serious side tho, I'm VERY rusty at my very rudimentary understanding of chemestry/physics, but IIRC water will stay liquid below 32 deg F. if it is under pressure (the reason Ice Skates work), so my thought would be that there must be a point where the pressure it is under and the temperature it will freeze at will match, at which point it will freeze without expanding, which I would guess would be significantly colder than 32F/0C.
 
#199
Geoff St. Germaine said:
A phase diagram of water will answer your question. You need more info than that to be able to answer your question. It could be any of your first two suggestions, but not the last one. The increasing pressure as the ice forms will reduce the freezing point of the water, but it depends how cold we are talking... just below zero, absolute zero or anywhere in between. Ahh second year chemistry, how I hate you.

Invalid Link Removed
Click to expand...

Ugh. Must you post phase diagrams?!

At least we aren't mentioning the 3-D phase diagrams from Thermo. Stupid Thermo....
 
#200
LajoieT said:
Why can it not freeze AND expand?

just because the material is unbreakable doesn't mean it cannot be stretched out as the ice expands.:D

On the serious side tho, I'm VERY rusty at my very rudimentary understanding of chemestry/physics, but IIRC water will stay liquid below 32 deg F. if it is under pressure (the reason Ice Skates work), so my thought would be that there must be a point where the pressure it is under and the temperature it will freeze at will match, at which point it will freeze without expanding, which I would guess would be significantly colder than 32F/0C.
Click to expand...

Interestingly enough, I was reading a paper the other day about why ice is slippery and it was saying that neither the reduction in the melting point by pressure, nor frictional heating explained what is happening with things like skating.

Aha... I found a website with the same thing on it. It appears that it's a "quasi-fluid layer". http://www.exploratorium.edu/hockey/ice2.html
 

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