Mathematical equations, physics buffs.

[Iggypoppin']

I said I'd start one!
general maths problems, equations, formulae, discussion on maths education methods, etc.
Physics equations, space time theories, Einstein etc. There's got to be some people interested and educated in this stuff. Graphs and other instruments encouraged to be posted!
For the record, there isn't a treadmill big enough, and if there was I think there are some people who would argue that friction would prohibit the plane from taking off.

[gtfpv]

anyone who thinks the plane wont take off better not post in this thread ,OK?

[buggo]

??? So if a planes going 300km/h on a treadmill, but 0km/h +- wind, earth rotation, relative to Earths surface, atmosphere, etc, it will take off ??? Can't see it happening, unless I have the wrong idea...

[flappist]

Originally Posted by buggo_gt

??? So if a planes going 300km/h on a treadmill, but 0km/h +- wind, earth rotation, relative to Earths surface, atmosphere, etc, it will take off ??? Can't see it happening, unless I have the wrong idea...

You have the wrong idea.

Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

Once the air flows fast enough to create a pressure differential between the top and bottom of the wing greater than the mass of the aircraft it will move upwards.

If the air is moving slower relative to the ground than the plane it will move up and forward, if the same it will just move up and if greater it will move up and backwards BUT IT WILL ALWAYS TAKE OFF

[GasoLane]

Originally Posted by flappist

Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

Once the air flows fast enough to create a pressure differential between the top and bottom of the wing greater than the mass of the aircraft it will move upwards.

If the air is moving slower relative to the ground than the plane it will move up and forward, if the same it will just move up and if greater it will move up and backwards BUT IT WILL ALWAYS TAKE OFF

Would that be like an old Tiger Moth with a top speed of about 60mph and flying into a 60mph headwind.

It's flying, but not getting very far?

[flappist]

Originally Posted by GasOLane

Would that be like an old Tiger Moth with a top speed of about 60mph and flying into a 60mph headwind.

It's flying, but not getting very far?

A person I know was once flying a Piper Tomahawk near melbourne during a 50 knot wind. He could not land as the stall speed of the aircraft was less than that and he was actually being blown backwards up the runway.

He had to waste time orbiting until there was a slight drop in wind speed and then did a flapless dive at the deck with several other pilots running out to shove blocks of wood on the wings to break up the lift so they could drag it off and tie it down.

[SteveJH]

Originally Posted by flappist

A person I know was once flying a Piper Tomahawk near melbourne during a 50 knot wind. He could not land as the stall speed of the aircraft was less than that and he was actually being blown backwards up the runway.

He had to waste time orbiting until there was a slight drop in wind speed and then did a flapless dive at the deck with several other pilots running out to shove blocks of wood on the wings to break up the lift so they could drag it off and tie it down.

If the runway was long enough could he have just landed with the wind in that case rather then against it?

[grandpa_spec_F6]

Originally Posted by flappist

You have the wrong idea.

Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

Right you are, this hypothetical also wouldn't work as there must be a force applied to the wings (wind) to generate lift, thus allowing to gain altitude. .

[Swordsman88]

I've seen that a=1 b=1 example before...its pretty obvious where the issue comes up because in the step 0/(a-b) leads to 0/0 and dividing by 0 brings up a world of issue that little trick ignores.... Still looks funny though...

Originally Posted by flappist

You have the wrong idea.

Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

Once the air flows fast enough to create a pressure differential between the top and bottom of the wing greater than the mass of the aircraft it will move upwards.

If the air is moving slower relative to the ground than the plane it will move up and forward, if the same it will just move up and if greater it will move up and backwards BUT IT WILL ALWAYS TAKE OFF

The problem with this question is while what you say is perfectly true, 99% of people ignore the little chestnut of 'maximum tyre speed'. This fact came up in a debate on a airliner forum where some bright chap pointed out that the mythbusters test (which is the only case i know of where this fact was atcually tested on full scale) would work for any size scale. Well not if you look at an airliner it might not.

Case in point. A medium loaded B767-300 has a takeoff speed (v2) of 150knots (roughly), so call it 172 mph. So if you pull the conveyor belt along at 172mph but apply thrust for takeoff than the 767 will take off...but the wheel speed is 2 x 172mph....Problem. Maximum tyre speed for a 767 is perhaps 190mph. Certainly i dont' know of any airliner tyre with greater than 210mph before it pops.

So in that test you'd pop all your tyres pretty quick and then assuming the rims dug into your mystical converyor belt than the takeoff would most likely never happen. These sorts of things just play on your perceptions...look at it critically and it all comes out in the wash...

[Jesmol]

Originally Posted by Swordsman88

Case in point. A medium loaded B767-300 has a takeoff speed (v2) of 150knots (roughly), so call it 172 mph. So if you pull the conveyor belt along at 172mph but apply thrust for takeoff than the 767 will take off...but the wheel speed is 2 x 172mph....Problem. Maximum tyre speed for a 767 is perhaps 190mph. Certainly i dont' know of any airliner tyre with greater than 210mph before it pops.

So in that test you'd pop all your tyres pretty quick and then assuming the rims dug into your mystical converyor belt than the takeoff would most likely never happen. These sorts of things just play on your perceptions...look at it critically and it all comes out in the wash...

Now there's a flaw in this logic. The scale argument cant be restricted to just the tyres. Sure there's an issue with maximum tyre speed, but there's an even bigger issue with building a conveyor that could hold a 767 and run at 172mph, therefore you could even do the experiment

[buggo]

Originally Posted by flappist

You have the wrong idea.

Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

Once the air flows fast enough to create a pressure differential between the top and bottom of the wing greater than the mass of the aircraft it will move upwards.

If the air is moving slower relative to the ground than the plane it will move up and forward, if the same it will just move up and if greater it will move up and backwards BUT IT WILL ALWAYS TAKE OFF

I know they aren't driven by their wheels, I'm not that delayed. They use engines to generate thrust, which makes them move foward.
If the plane is on a treadmill, they do not need to be on, because the treadmill is spining the wheels at the same speed the engines would.

If the plane is on a treadmill, the air is moving no faster nor slower than it was before the plane was on the treadmill. If it did not take off before getting on, what are spinning wheels going to do?

And yeah I know how an areofoil works, in theory, I did a whole term just on that shape.

Please tell me we are talking about complete different scenarios
Like the treadmill moves or something.

[flappist]

Originally Posted by buggo_gt

I know they aren't driven by their wheels, I'm not that delayed. They use engines to generate thrust, which makes them move foward.
If the plane is on a treadmill, they do not need to be on, because the treadmill is spining the wheels at the same speed the engines would.

If the plane is on a treadmill, the air is moving no faster nor slower than it was before the plane was on the treadmill. If it did not take off before getting on, what are spinning wheels going to do?

And yeah I know how an areofoil works, in theory, I did a whole term just on that shape.

Please tell me we are talking about complete different scenarios
Like the treadmill moves or something.

You all get this fixation that the "treadmill" will stop the forward motion of the aircraft.

It does not as all it does is spin the wheels, the plane moves relative to the air, the only reason it has wheels is to reduce friction with the ground.
Floaty, ski and SSH aircraft doen't even need wheels.

Assuming no bearing friction and indestructable treadmill and wheels the treadmill and wheels will spin at an infinite rate but the aircraft will still move forward as it pushes against the air not the ground....

If the treadmill and wheels obey the normal laws of physics it will be up to whether the treadmill or wheels fail first.

Grab a pushbike and hold it on a moving walkway. From outside the walkway grab the frame and start rolling it forward. If the walkway speeds up what happens?

The pushbike wheels spin faster, that is all.......

[buggo]

Originally Posted by flappist

You all get this fixation that the "treadmill" will stop the forward motion of the aircraft.

It does not as all it does is spin the wheels, the plane moves relative to the air, the only reason it has wheels is to reduce friction with the ground.
Floaty, ski and SSH aircraft doen't even need wheels.

Assuming no bearing friction and indestructable treadmill and wheels the treadmill and wheels will spin at an infinite rate but the aircraft will still move forward as it pushes against the air not the ground....

If the treadmill and wheels obey the normal laws of physics it will be up to whether the treadmill or wheels fail first.

Grab a pushbike and hold it on a moving walkway. From outside the walkway grab the frame and start rolling it forward. If the walkway speeds up what happens?

The pushbike wheels spin faster, that is all.......

I must be using different treadmills, the ones I use do not move 1mm foward, backward or sideward. Yet I run Km's without getting anywhere???
Or do you mean it's on a conveyor belt that moves in the same direction at the same speed as the plane? So wheels aren't moving, yet the plane itself is, in that case yeah of course it will fly.

[sudszy]

Originally Posted by flappist

You have the wrong idea.
Aircraft do not accellerate due to power being applies to the wheels, the accellerate because they push against the air.

I prefer to think the forward motion as being much like the reason for lift.
The propellor causes a decrease in pressure in front of the aeroplane....but no big deal

Originally Posted by flappist

Grab a pushbike and hold it on a moving walkway. From outside the walkway grab the frame and start rolling it forward. If the walkway speeds up what happens?
The pushbike wheels spin faster, that is all.......

I think that example demonstrates it very well indeed, and if the you applied the brakes on the bike, then you'd might have trouble holding on to the bike and/or need to apply a much greater force to be able to drag it along, just as the aeroplane might need a bit more thrust if its going to be able to move if its tyres were locked up causing friction against the ground.

Of course its going to be marginally harder for the plane to take off on the conveyor belt because the force of rolling friction is basically going to at least double if the wheel speed doubles.

[Rodp]

Originally Posted by buggo_gt

??? So if a planes going 300km/h on a treadmill, but 0km/h +- wind, earth rotation, relative to Earths surface, atmosphere, etc, it will take off ??? Can't see it happening, unless I have the wrong idea...

Mythbusters created a treadmill large enough to test a small plane - it took off.

The thrust is not provided by driving wheels, the wheels are inconsequential beyond minimising friction between the ground. The thrust is generated via air being propelled by propeller, jet or <insert Area 51 tech here>

[FGII-XR6]

Originally Posted by buggo_gt

??? So if a planes going 300km/h on a treadmill, but 0km/h +- wind, earth rotation, relative to Earths surface, atmosphere, etc, it will take off ??? Can't see it happening, unless I have the wrong idea...

zero lift will be acheived as lift is caused by airspeed differential between the top and bottom of the airfoil creation a low pressure zone above the wing, the higher pressure below the wing then provides lift. aerodynamics 101

[SEZ213]

Originally Posted by Iggypoppin'

I said I'd start one!
general maths problems, equations, formulae, discussion on maths education methods, etc.
Physics equations, space time theories, Einstein etc. There's got to be some people interested and educated in this stuff. Graphs and other instruments encouraged to be posted!
For the record, there isn't a treadmill big enough, and if there was I think there are some people who would argue that friction would prohibit the plane from taking off.

Well, you started this thread...what's the first question...

[Iggypoppin']

Solve for x

8(3/9)/.002([4xG]pi x 9)
--------- =x
T^3(Gx4)/5

where G is gravity acting on how lazy I am, pi is PI as in the number 3.14 etc, and T is me not caring anymore but given a numerical value. Which is also unknown.

[shedcoupe]

Originally Posted by Iggypoppin'

Solve for x

8(3/9)/.002([4xG]pi x 9)
--------- =x
T^3(Gx4)/5

where G is gravity acting on how lazy I am, pi is PI as in the number 3.14 etc, and T is me not caring anymore but given a numerical value. Which is also unknown.

Well, assuming that G = 9.8 m/s² and pi = 3.142, and T = obviously it must be zero, then the answer is : x = 'with a chicken'.

[SEZ213]

Originally Posted by shedcoupe

Well, assuming that G = 9.8 m/s² and pi = 3.142, and T = obviously it must be zero, then the answer is : x = 'with a chicken'.

I got a duck...

[shedcoupe]

Originally Posted by Sezzy

I got a duck...

You forgot to carry the goose and add the first number you thought of .....

[v gate]

Originally Posted by Sezzy

I got a duck...

as far as i can tell your way ahead with the duck.
everyone knows chickens suck at flying.

[Airmon]

Originally Posted by shedcoupe

Well, assuming that G = 9.8 m/s² and pi = 3.142, and T = obviously it must be zero, then the answer is : x = 'with a chicken'.

Bad assumption. 'G' is traditionally Newtons Gravitational constant (among other things but in this context) not 'g' which is gravity in your frame of reference. Which would be 9.81 but would depend on your altitude above sea level and then you can use G to calculate g
Been so long I cant remember G, its quite large from memory.

Originally Posted by Work Horse

Oldie but a goodie

a = 1, b = 1

a = b
a^2 = b^2
a^2 - b^2 = 0
(a-b)(a+b) = 0
(a-b)(a+b)/(a-b) = 0/(a-b)
1(a+b) = 0
(a+b) = 0
1 + 1 = 0
2 = 0
1 = 0
1 + 1 = 1

You can't divide zero or divide anything by zero. You would need to simplyfy out (a-b)(a+b) and add or subtract anything to the other side.
Hence the assumption 1=0 etc is false.

As for the Airplane taking off, I dont know enough about Aerofoils to hazzard an accurate conclusion and am not involved in Aeronautics.
However I would think that if you could take off in a plane on the spot someone would be using it? Would be helpful for say Aircraft carriers. This is however not going to work as planes like that use Jets and thrust to gain air speed to gain lift.
The debate would be more whether a propellor passes a large enough volume of air at a large enough speed to gain lift. I wouldnt expect a Jet-turbine to do that, but again, don't know enough on the subject to say for sure, can only speculate.



And sound is not relative like light.


Here's one for you, is Light a particle or a wave????? No fence sitting!

[LukeyST]

Originally Posted by Airmon

As for the Airplane taking off, I dont know enough about Aerofoils to hazzard an accurate conclusion and am not involved in Aeronautics.
However I would think that if you could take off in a plane on the spot someone would be using it? Would be helpful for say Aircraft carriers. This is however not going to work as planes like that use Jets and thrust to gain air speed to gain lift.
The debate would be more whether a propellor passes a large enough volume of air at a large enough speed to gain lift. I wouldnt expect a Jet-turbine to do that, but again, don't know enough on the subject to say for sure, can only speculate.

Here's one for you, is Light a particle or a wave????? No fence sitting!

Lift only comes from relative air speed. Thats why planes take of into the wind, 'free speed' basically. And im pretty sure they use this technique on aircraft carriers also? Both using windspeed and ship speed. So if there is a wind of say 50km/hr and the ship is capable of 25km/hr they put they ship into the wind and have a 75km/hr windspeed advantage, if you need 300km/hr airspeed to take off that means you would then only need to be going 225km/hr (relative to the ship deck) to take off.

If they dont use this method they should lol, but im confident they do.

On the light particle thing, isnt light supposedly photon's? which is a mass-less particle. The theory of it being mass-less falls apart though when u consider gravity can bend light, and to be effected by gravity you need a mass......

Im going with its a particle (photons), but unsure about the whole 'mass-less' thing.

[In Focus]

If you're starship is travelling at the speed of light, what happens when you turn on the headlights?

[Iggypoppin']

Originally Posted by In Focus

If you're starship is travelling at the speed of light, what happens when you turn on the headlights?

The light will get to x before you do. X being the destination and light being faster than I could actually travel, I will allow the possibility that I am travelling at 185,000m/ps(mps=miles per second) speed of light is 186,000mps, so the light from the headlights will reach x before I do.

[flappist]

Originally Posted by In Focus

If you're starship is travelling at the speed of light, what happens when you turn on the headlights?

Well the headlights are also travelling at the speed of light so relative to the starship they just work normally but relative to you depending on your reference point they may appear to do many different things. They won't ACTUALLY do different things just look like they are.

It is all about reference.

You are on the side of the road.
A car drives past at 100km/h with the horn blowing.
The frequency of the horn changes as it goes past but the driver does not hear any difference.

Did the horn change or not change?

[Iggypoppin']

Originally Posted by flappist

Well the headlights are also travelling at the speed of light so relative to the starship they just work normally but relative to you depending on your reference point they may appear to do many different things. They won't ACTUALLY do different things just look like they are.

It is all about reference.

You are on the side of the road.
A car drives past at 100km/h with the horn blowing.
The frequency of the horn changes as it goes past but the driver does not hear any difference.

Did the horn change or not change?

physics own laws defy this question. As only light can travel at the speed of light, the question can't be applicable and thus I can alter it how I wish
anyone want to help me pierce space time with a gravity drive and travel to proxima centauri?

[grandpa_spec_F6]

Originally Posted by IggyPoppin'

physics own laws defy this question. As only light can travel at the speed of light, the question can't be applicable and thus I can alter it how I wish
anyone want to help me pierce space time with a gravity drive and travel to proxima centauri?

No...

[GasoLane]

Originally Posted by flappist

You are on the side of the road.
A car drives past at 100km/h with the horn blowing.
The frequency of the horn changes as it goes past but the driver does not hear any difference.

Did the horn change or not change?

Oh-Oh... I can see Schrodinger's cat making an appearance (or not) soon