How a fly can stop a train

[TeePee]

The part of the wheel which is in contact with the track never moves, unless the train is wheelspinning.

[GreenPiggy]

Well, if the question is based on a supposition that is basically untrue outside of one extreme example, then it's pretty nonsensical surely?
Rich :¬)

The point being that the time explanation works for all examples not most of them. Newtons laws hold true for 99.999% of examples but break down towards physical extremes. It doesn't make them correct.

[Rave]

The point being that the time explanation works for all examples not most of them. Newtons laws hold true for 99.999% of examples but break down towards physical extremes. It doesn't make them correct.

O.K., so my explanation doesn't work for subatomic particles, but it works for all atomic matter. Since we started off talking about trains and flies, I don't think it really needed a disclaimer, especially since loose quarks don't tend to exist outside of stars and particle accelerators. Newtonian physics can model the interaction between the two objects perfectly adequately.

Rich :¬)

[Rob]

The part of the wheel which is in contact with the track never moves, unless the train is wheelspinning.

Umm... The point of contact rotates around the circumference as the wheel turns. If the same part stayed in contact it would be pretty worn down after 200 miles


*edit* Unless you mean "The Bottom"

[TeePee]

The point of contact doesn't rotate or move at all. The top of the wheel is never in contact with the track now is it? Makes a lot more sense than a fly stopping a train!

[turkster]

Yeah but the TOP of the wheel is variable. It is not like you are defining a fixed point on the wheel and saying that doesnt move.

[Rob]

The point of contact doesn't rotate or move at all. The top of the wheel is never in contact with the track now is it? Makes a lot more sense than a fly stopping a train!

Sorry, missed 'point of contact' point. Doh!

[Knoxville]

Would anyone like to explain wtf a quark is?

[turkster]

Yeah its a bit complicated but check this out .

The whole site is pretty interesting.

[Rob]

I like "The sixth flavor of quark". Used to get quite into this stuff. Then I gave up pot

[Skii]

The train would definately stop if it was a Virgin train..

[Rob]

The train would definately stop if it was a Virgin train..

[Rave]

Yeah its a bit complicated but check this out .

The whole site is pretty interesting.

Great link!

I've just had to stop reading as I started to wonder where all those fundamental particles came from- that inevitably leads to brainache in my experience. Quick, distract me!

Rich :¬)

Edit: LOL at Skii

[turkster]

Yeah I got interested in quantum physics about a year ago when I picked up a dictionary of Quantum physics. Designed for the general public but interesting nonetheless.

[turkster]

Great link!

I've just had to stop reading as I started to wonder where all those fundamental particles came from- that inevitably leads to brainache in my experience. Quick, distract me!

Rich :¬)

Edit: LOL at Skii

Yeah I know that is the problem with those didctionary type things, you have to keep following things up and it just goes downhill from there

[Auran]

I thought that they couldn't solve Xeno's Paradox of Achilles and the Tortoise, until they developed infinity theory, i.e. that they are not all the same size

In the case of the train and fly, if you reduce the timeframe enough, i.e. zero, then neither will be moving. But in real terms the trains slows by a tiny fraction and the flies direction changes rather rapidly - conservation of momentum and all that

Newtons laws of mechanics only hold true up to about a tenth of the speed of light (18300m/s), i.e. first gear for most sub-atomic aprticles

When I did physics at university I didn't mind quantum theory and relativity. It was thermodynamics that used to p*** me off, apart from the fundamental laws the rest of it seemed to be based on approximations. Oh and I hated doing differentiation in three dimensions