Weirdness of the wheels

[Airframes]

Ah! So if we coat them in Teflon, they won't stick ...... I'll close the door on the way out!!

 

[mikewint]

Actually, Terry, Polytetrafluoroethylene (PTFE) is another polymer very similiar to the aforementioned PVF. The monomer is Tetrafluoroethylene (TFE) a really fun compound that explodes quite dramatically on contact with oxygen or when heated. Even the heat generated by compression is enough to detonate the TFE.
Most people think PTFE is a product of the space program but is was actually discovered serendipitously in 1938 and patented by DuPont back in 1945. Its low friction and chemical resistance was used in the Manhatten project to coat valves exposed to the uranium terafluoride manufacture.
Don't think it would help your tires though as teflon is a solid

 

[fubar57]

Wow Mr. Science....tell us more. JK, great stuff Mike. I learn something new every day here. Thanks.

Geo

 

[Capt. Vick]

Check out the big brain on Mike!!!

 

[N4521U]

What he said.......
Cuz I couldn't understand one syllable!
Still don;t know why it's sticking.

 

[mikewint]

OK, let's define some terms: Adhesion- two dissimilar substances stick together, i.e. water droplets adhere to your skin. Cohesion-two similar substances stick together, i.e. water molecules stick to water molecules which is why the droplets form to begin with. Cohesive forces form the drops while adhesive forces cause the drops to stick to your skin. OK, so far?
The forces mentioned above are pretty much the same forces and are the same electrostatic forces that hold atoms together or form chemical compounds, i.e. negative attracts positive and vice versus and the magnitude of the attractive force depends upon distance. Actually the square of the distance, like gravity, double the separation and the force is reduced by 1/4th conversely reducing the distance by half increases the force four-fold.
Next solid surfaces, all surfaces contain pits, grooves, cracks, crevasses, hills, and valleys. Think of two sheets of coarse sand paper. To pull one sheet across another requires a lot of force as the hills of one sheet fall into the valleys of the second and have to be dragged up and over. Smooth the surfaces, lower hills and valleys, less up and over, less force. Seems as if really smooth surfaces should slide across each other with little or no force however the reverse is true. Extremely smooth surfaces lock together and become very difficult to move. Think two sheets of very clean glass or two highly polished metal plates.
OK, now back to the beginning. As two surfaces approach each other electrical forces increase with the square of the distance until the attractive increase is sufficient to pull electrons from one atom into another either completely or partially. This complete or partial removal of electrons is a chemical bond.
Now your tires: Polymers are held together by the chemical bonds formed between the monomer and the cross-linker. A massive cohesive network bond over the entire polymer.
Put your polymer tire in contact with a dissimilar surface and hill meets valley on a small scale resulting in small adhesive forces. Over time as the cross-links fail released monomers flow downward (gravity) filling more valleys and crevasses, thus, increasing adhesion. The tire is becoming more and more stuck to the surface it is on.
You can see the same effect with adhesive tapes. The adhesive compound is a liquid with very, very high viscosity (cohesion) which chemically bonds to the tape substrate. Put the tape on a surface and the liquid adhesive flows into the crevasses and valleys of the surface forming bonds with it. Over time there is more flow into more valleys and crevasses, the tape becomes more and more difficult to remove. You can easily see the electrical nature of the bonding by pulling cellophane tape off a surface in a very dark room, once your eyes are adapted. Watch the tape junction and you will see the sparks as electrons return to their parent atoms.
All interactions in the man-sized world are electrical interactions as electrons repel each other and/or attract atomic nuclei of their own or other atoms. Solids are really not as atoms are 99.99999% dead empty space so are the "solids" they make up. Everything is almost entirely empty space. Solidity is an illusion brought about by electron repelling electron prevent closer approach

 

[Airframes]

What really puzzles me is, if Teflon is non-stick, then why does it stick to frying pans? I'll close the outer door too .......

 

[mikewint]

Terry, like an English Muffin the secret is in the "nooks and crannies" The fluorine atoms line the outside of the carbon chain backbone of the PTFE molecule. Fluorine does not release electrons easily thus PTFE is almost chemically inert (bonds do not form easily thus the low friction). Thus PTFE will not in and of itself stick (bond) to a metal pan. BUT if the surface of the pan is sand-blasted and coated with a primer the PTFE can be mechanicly embeded into the primer. Thus the PTFE coating is fragile and quite subject to mechanical abrasion.

 

[N4521U]

Well...............
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why didn't you say That the first time..... duh
I will read thru it again. It's starting to make sense. I really didn't know how bonding and sticking took place, stuff just sticks, or doesn't.

So the PTFE flows into the english muffin texture, and turning into a solid, will not release? Kinda like a bad dentist applying a filling on a smooth surface, nothing to anchor to?
.
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So where do you teach?

 

[mikewint]

N45, actually everything sticks, it is just a matter of degree. As molecules approach electrons move to get away from each other. Thus at any instant of time there will be more electrons on one side of the molecule as compared to the other. The molecules have become transient dipoles (two poles, one + with respect to the other which is -). the + end of one dipole attracts the - end of the other. As the number of electrons around the molecule increase the transient nature of the unequal electron distribution lessens and the molecules remain dipolar for longer periods of time.
So when your shoe touches the floor it chemically bonds to the floor. To move the shoe requires force to break the bonds. We call it friction

 

[BikerBabe]

...what's the colour of friction? Yeah yeah, I know...*follows after Terry going out of the doors*

 

[meatloaf109]

Friction is one of my favorite activities.
Mike, I stand in awe of your command of chemestry.
Now, how does gravity work?

 

[mikewint]

One at a time. Maria, color of friction, depends upon the context. Do you mean color as a human perception initiated by cone cells in the retina being stimulated by the reception of specific energy photons or color as a property.
Perception: the retina contains 3 types of cone shaped cells that trigger at specific energies. The lowest energy photon that will trigger a cone cell is 0.000000000000000000276 Joules. When this energy content photon triggers a specific cone cell we perceive the color RED. Two other types of cone cells trigger at the medium energy photon GREEN and the higher energy photon BLUE. Note that in order to perceive a color photons must actually enter the eye. This can occur directly or indirectly by reflection off a surface. Visable light photons have wavelengths ranging from long 750nm to short 380nm. Longer than 750nm photons contain too little energy to trigger a cone cell thus the "light" is not visible (infra-red (heat)). Shorter than 380nm contain so much energy they begin to penetrate human tissue (ultra-violet radiation) and also to not trigger any cone cells. The excessive energy can actually destroy the cells. Reflecting a photon requires that the object be larger than the wave length of the photon else the wave just "wraps around them"(observe water waves wraping around a pier piling but reflecting off a wall. Thus objects smaller than 380nm cannot reflect a photon and cannot have color or be seen for that matter using visible light. To "see" objects smaller than 380nm requires shorter wavelengths such as the wavelength of an electron. Virus particles range from 5 to 300nm. To "see" them requires a 10kV TEM (Transmission Electron Microscope) which produces electron wavelengths of 12.3pm.
This is all moot to your question since friction is a force not an object capable of reflecting or generating photons of visible light. Although the objects experiencing friction can heat up and generate IR radiation and if heated enough Red, Orange, or Yellow visible light photons

 

[mikewint]

Meat, even easier, it doesn't. It does not exist as a force any more than centrifugal force, as a real force, exists. In a car going around a curve you seem to experience a real force pulling you to the outside of the curve, "Aha" you say, "centrifugal force". Step outside the car and watch from above and you can clearly see that the car moves around the curve while the passengers continue in a straight line. The car is curving out from under them until the outside door smacks them in the arm and then pushes them around the curve.

 

[Airframes]

And gravity is a myth - the Earth sucks !

 

[mikewint]

Terry, indeed it does. Had that inscribed on my Zippo wayback in 1965
Actually the presence of a mass distorts the fabric of spacetime causing it to curve. The greater the mass the greater the curvature. The earth curves spacetime and the moon simply follows the curvature around the earth. No force needs to act upon it. in a similiar fashion the sun produces a much larger distortion in spacetime. The earth simply follows the curvature around the sun, again noforce needed. Beams of light also follow the curvature allowing asronomers to see stars behind the sun during an eclipse. Note that the curvature is in spaceTIME which means that time flows slower on the sun relative to earth. Nuclear processes take more time on the sun than the same process on earth. Both of these have been directly observed comfirming the predictions of General Relativity

 

[Airframes]

So I'd have more time to complete a model if I lived on the Sun?
Hang on, that wouldn't - the plastic would melt!

 

[mikewint]

Unfortunately since you are within the time flow you would only notice your rate of flow RELATIVE to another's time rate. That's why it is called the Theory of RELATIVITY. Everything is relative. There is no privileged position to view anything. Sitting motionless at your computer you might be tempted to say you were stationary but in fact the Earth is revolving on its axis, rotating around the sun, the solar system is revolvng around the Galactic core, and the Galaxy is moving through the universe.
So on the sun one hour is still one hour. If I, on the Earth were viewing you, you would appear to me moving much slower and if you viewed me on the Earth you'd wonder why I was moving so fast. Tick and tock are events that occur in time. We actually have no way to measure time other than through counting events.

 

[meatloaf109]

And the grey hair.

 

[mikewint]

Remember biolgical processes are also events and goverened by the local time flow. Two identical twins on earth, one get on a starship and heads toward a star 20 ightyears distant. The ship travels 99.9% the speed of light. On the ships return the earth twin is an very old man but the starship twin has only experienced 4 years in his time frame and is still a young man. Tis all relative