Neutrino apparently moving faster than light

[cjo]

I think he is trying to make a different point. His argument is that the belt causes air above the belt move fast enough that the plane cannot get lift to fly. What I don't buy is that the belt would cause the air move in such a way. The belt just doesn't have the kind of form and surface that would cause the air move in a way that would affect a plane significantly.

No, that is not the point I am making. Please show me where I said that the belt causes the air itself to move (apparently twice now)

 

[hoho]

I think his point really was that the belt won't matter at all because as it was said in the beginning right after he wrote that the wheels have nothing to do with the actual liftoff mechanisms of the plane.

Also, if the belt would through some miracle cause strong airflow that is opposite to the expected plane movement speed then the plane WILL take off even easier* as it won't have to use as much engine power to generate enough lift as the belt will do it

*) and probably crash as soon as the airflow from belt is not strong enough any more

 

[Davros]

The answer is the plane will take off
(If it got its forward motion from the wheels it wouldn't)
but as the wheels freewheel it doesnt matter how fast you move the belt you wont stop the plane from moving forward
you can do this at home if you have a belt sander and a toy car
push a car along the belt with your finger
now turn on the sander you will notice 2 things. wheel speed and forward speed are independent and it doesnt require any more force to push the car forward (actually it does you need to compensate for friction, but the amount is tiny)

I got that (although more detailed) answer from an actual physicist

 

[cjo]

This requires that the belt be going extremely fast in the opposite direction.
Unlike with a car, the driving force is engine thrust that is weakly linked to the ground via friction and rolling resistance in the wheels.
Because of this, the belt must race back far faster than the unimpeded takeoff speed of the plane.

Under somewhat realistic scenarios, the belt could not race back fast enough to provide enough force such that a small fraction of it indirectly fed through the landing gear can equal the plane's direct thrust.

Good point. Although in a thread that talks about trains accelerating instantly to the speed of light, I find the phrase "Under somewhat realistic scenarios" amusing

 

[Arwin]

The answer is the plane will take off
(If it got its forward motion from the wheels it wouldn't)
but as the wheels freewheel it doesnt matter how fast you move the belt you wont stop the plane from moving forward
you can do this at home if you have a belt sander and a toy car
push a car along the belt with your finger
now turn on the sander you will notice 2 things. wheel speed and forward speed are independent and it doesnt require any more force to push the car forward (actually it does you need to compensate for friction, but the amount is tiny)

I got that (although more detailed) answer from an actual physicist

Heh, nice one. And so obviously true once you realise that the wheels don't accellerate the plane at all and the engine pushes against the air to propel itself and (almost) nothing else.

 

[Davros]

Let me guess you found your belt sander

Now what happens when a neutrino is rolling along a conveyor belt that moves backward to match its forward speed

 

[ninelven]

but as the wheels freewheel it doesnt matter how fast you move the belt you wont stop the plane from moving forward

And this has always been my problem with BS physics questions, at some speed the tires on the wheels will no longer hold together, effectively grounding your plane.

 

[Davros]

oh, you mean if the belt moves at 100,000mph the tires may burst, yes I can see how that would be a problem

 

[Arwin]

And this has always been my problem with BS physics questions, at some speed the tires on the wheels will no longer hold together, effectively grounding your plane.

Actually then the plane will be catapulted in the other direction

 

[Mize]

This whole thread is so freshman physics.

 

[Davros]

Ok then
Q: How many quantum physicists does it take to change a light bulb

A: None, because if they know the bulb needs changing they cant possibly know where it is....

 

[tabs]

They can have a good guess though.

 

[Mendel]

I always thought along the lines of photons must have mass, because E=MC2. If photons have no mass, then they have no energy. I always thought they do have energy, therefore they must have mass. But then I´m thinking too simple.

 

[hoho]

Photons olny have mass when they move. When they stand still (is that even possible?) they have zero mass.

 

[Ethatron]

Do they move at 0K?

 

[hoho]

To get absolute zero you can't have any movement because that would indicate kinetic energy and (simplifying a bit) kinetic energy = heat -> not absolute zero

 

[Gubbi]

Photons olny have mass when they move. When they stand still (is that even possible?) they have zero mass.

Photons don't have mass.

They do have momentum.

Cheers

 

[tabs]

Photons don't have mass. They do have momentum.

then what is moving?

 

[Gubbi]

then what is moving?

Sorry, WHAT?

Stop thinking of photons as tiny marbles. They are photons.

Cheers

 

[rpg.314]

Photons have a mass and they can generate gravitational attraction and everything, but they don't have rest mass.