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[Teh Fluff]

But... the plane does take off from the treadmill, they did it on Mythbusters.

.. watches video (http://youtu.be/0ul_5DtMLhc)

"Mythbusters" Pah! Mythpersistence more like.

They cheated! The plane was not stationary in relation to a fixed point on the ground. They also did not conveniently mention a headwind.

For a plane to fly it needs lift generated by air flowing over the wings. If it is truly stationary (with no ambient wind) then no lift will be generated. Granted a small amount of airflow may be generated by the treadmill dragging a cushion of air around with it but I suspect nowhere near enough to fly. Even if it was enough it would be followed by a stall and a crash.

[Guilt]

To be honest the mythbuster experiment shows no real valid data anymore than a boat being able to accelerate up a river against the current would.  A tethered glider would have been far more appropriate.

Because plane wheels are essentially free wheeling the relative loss in forward propulsion from the propeller would be negliable. I would guess that the planes acceleration would only intially be effected and that takeoff speed was same as if on a stationary runway.

[DeadlyAvenger]

Dead fish can swim upstream. Fact.

[Brahms]

What guilt said, the plane wheels are free wheeling so no matter how fast you move the treadmill, the plane can still move forward. It's like putting a toy car on a treadmill, you can push the toy car forward using hardly any force no matter how fast the treadmill turns.

[Mr Chug]

The plane on a treadmill is a classic case of the result being entirely dependent on your interpretation of the question; if you use the speed of the wheels as the speed of the treadmill the plane will not move and will therefore not take off, whereas if you base it on the typical speed of the entire plane then as said, the wheels will simply spin twice as fast (assuming zero friction) and the plane will take off anyway (assuming you have a long enough treadmill).

[e90]

As far as I can work out, all the crumple zones do is change the time over which the cars accelerate. So yes, they do reduce the forces but those forces will still act to cancel each other in all the cases with the identical cars.

Agreed, except I disagree about the 'all' they do is alter the time.  The also absorb the energy, which is needed to change the form of the steel/plastic in the chassis, so I would have thought that less energy remains to go else where.

Which also effects the elastic band position at the beginning of the thread?

[Yer man oer yonder]

Agreed, except I disagree about the 'all' they do is alter the time.  The also absorb the energy, which is needed to change the form of the steel/plastic in the chassis, so I would have thought that less energy remains to go else where.

Which also effects the elastic band position at the beginning of the thread?

When I say the energy is dissipated, a lot of it does go into the deformation of the chassis. The energy being dissipated is mostly kinetic energy (E = (m*v²)/2). So the change in kinetic energy is proportional to the change in the velocity squared. If the chassis didn't deform the car would come to a stop almost immediatly with the energy being dissipated by other means. But the deformation takes time therefore it takes time for the kinetic energy (and velocity) to go to 0. But the only way in which this affect the forces acting on the car is that the rate of energy dissipation controls the acceleration. If it takes longer to dissipate the energy the car accelerrates at a slower rate reducing the force. And since the change in velocity is still going to be the same the only way to decrease the accleration is to have that velocity change take place over a longer time interval. That's why I say that all the crumple zones do is change the time.

Also I don't see any mention about elastic bands. Perhaps you mean elastic collisions?

[Jebus]

Not really sure if this should go in here.... but thought some of these were interesting anyways. Heard of most of them but a few new ones: http://listverse.com/2010/05/28/11-brain-twisting-paradoxes/

[Mr Chug]

Topically, Zeno's paradox (the arrow one) is actually a pretty good way to intuitively understand a phenomenon in quantum physics called quantum decoherence (although the phrase 'a watched pot never boils' is even better). When you perform a measurement of state on, say, an electron excited to a higher energy level, also known as an exciton*, it forces the wavefunction into a pure state of 'this is an exciton'. From there, external interference causes the wavefunction to spread or to use the technical term, decohere, potentially allowing the exciton to de-excite UNLESS you continuously perform that same measurement as fast as possible, as this locks the exciton unable to de-excite!


*an exciton is technically both the excited electron and the absence of an electron that it leaves behind, but that's a topic for another lecture

[Zarf]

Anyone else get annoyed at the overuse of Schroedingers cat references in modern media?

[Tommy the Cat]

I like cats.

[mode_seven]

Anyone else get annoyed at the overuse of Schroedingers cat references in modern media?

Only when the original intent of the thought experiment is thrown out the window.

[Rct33]

Anyone else get annoyed at the overuse of Schroedingers cat references in modern media?

Only when the original intent of the thought experiment is thrown out the window.

And when it gets explained wrong/badly.

[Lullaby]

I liked it when it was mentioned at Big Bang Theory. I like Penny.

[Power]

Anyone else get annoyed at the overuse of Schroedingers cat references in modern media?

Both.