Long rod question

Le_Petit_Lapin said:
No, you don't.

You generate motion by, shoving your feet against the ground.

Planes on the other hand shove their props/jets against air.



Jets are the same, all they do is "Suck, Squeeze, Burn and Blow." Makes air flow backwards.
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No jets are totally different. Please read up on newtons third law. A jet engine is a beautiful implementation of this law. Yes jet engines suck, squeeze burn and blow BUT the forward motion comes from reaction against the hot expanded fast moving gases being shoved out the back of the engine, not by these gases thrusting AGAINST anything.
 
Le_Petit_Lapin said:
No, you don't.

You generate motion by, shoving your feet against the ground.

Planes on the other hand shove their props/jets against air.



Jets are the same, all they do is "Suck, Squeeze, Burn and Blow."

Air gets shoved out backwards, plane gets shoved forwards in reaction.
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Edit..
Ninja edit
 
Question. If the treadmill was spinning at the same speed as the WHEELS of the plane, would it take off?

I know it would take of if it were moving at the speed of the PLANE.

Am I correct in thinking it would not?
 
No. If it moves at the speed of the wheels, then surely it cannot start moving.

In the case of the plane, the wheels are moving at a different speed to the treadmill, in my question, they are not.
 
Hxc said:
Question. If the treadmill was spinning at the same speed as the WHEELS of the plane, would it take off?

I know it would take of if it were moving at the speed of the PLANE.

Am I correct in thinking it would not?
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The earth would reach critical mass. Thus you the earth and your ****ing treadmill would be vaporised!
 
the wheels of the plane move at the same speed as the plane, on tarmac.

the plane will take off unless the treadmill moves so fast that the friction force in the wheels is equal to that of the planes engines/prop - which is pretty much impossible, since the whole point of wheels is to reduce friction.

I recon a sea-plane on a treadmill could probably take off if it had big enough engines - It would just wreck the bottom of the plane.
 
The original post in this thread reminds of something I read at school to explain the difference between speed of electrons and speed of electricity.

Imagine a tube aross America from the East coast to west coast filled with tennis balls. You slowly push in an extra tennis ball at the east coast and a tennis ball immediately slowly drops out of the tube at the west coast.

"Electricity" has almost instantaneously flowed across America. An "Electron" has moved a few inches.
 
RIGHT!...............One aeroplane, one chopper, two treadmills on the moon with one FREAKING BAR.























Is this like an old No Swearing! bar, or a nice 'shiny' bar?............................... (my precious):)
 
Hxc said:
Question. If the treadmill was spinning at the same speed as the WHEELS of the plane, would it take off?

I know it would take of if it were moving at the speed of the PLANE.

Am I correct in thinking it would not?
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In what odd situation would the wheels not be moving at the same speed?

Bar skidding...


EffBee said:
No jets are totally different. Please read up on newtons third law. A jet engine is a beautiful implementation of this law. Yes jet engines suck, squeeze burn and blow BUT the forward motion comes from reaction against the hot expanded fast moving gases being shoved out the back of the engine, not by these gases thrusting AGAINST anything.
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Not entirely. The primary form of thrust generated by a jet engine is from its spinning turbines. The fuel burn adds to this very slightly, but not greatly. The point of the burning fuel is to get the turbine spinning, not to trigger a 3rd law reaction force (ie. rocket engine). Hence the reason why you now get jet-powered tanks and such. The burning fuel is used to turn a turbine which itself turns the drive shaft. In this scenario though, your reaction force is wasted.
 
tim80bwi said:
They both work in exactly the same way...

A prop/turbine blade turns and deflects air in a given direction. The only thing that changes is the way in which the rotational motion is created.

You may be thinking of a rocket engine :confused:
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Jet engines and rockets work in a very similar way at the level of basic physics.

A propellor is a completely different thing. Imagaine a cork screw going into the cork in a bottle of wine. As you turn the screw the bottle opener travels down into the cork. An airscrew is exactly the same - as you turn the prop it bites into the air and drags the plane forward.

The well know Archimedes screw does the same except the screw assembly stays still and the medium (water) moves past as the screw turns.

If you look at Da Vinci's sketch for a proposed helicopter it was basically a modified archimedes screw on top of a pilot's seat assembly instead of the rotor blades we use today. Pure genius for it's day.
 
tim80bwi said:
In what odd situation would the wheels not be moving at the same speed?

Bar skidding...




Not entirely. The primary form of thrust generated by a jet engine is from its spinning turbines. The fuel burn adds to this very slightly, but not greatly. The point of the burning fuel is to get the turbine spinning, not to trigger a 3rd law reaction force (ie. rocket engine). Hence the reason why you now get jet-powered tanks and such. The burning fuel is used to turn a turbine which itself turns the drive shaft. In this scenario though, your reaction force is wasted.
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I thought it was important to get gas expansion and therefore increase the velocity of the exhaust gases (?).
 
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