a strange question about tires and air

Here`s what I`m wondering, does the air in your vehicle tires rotate with the tire and at the same speed as the tire or does it just sit there without moving much?

I imagine that the air molecules in contact with the rubber inside of the tire probably move but what about the rest of the air does it move?

I guess another way to look at it is if there was a fly inside your tire would he be able to fly around in there while the vehicle is moving at 60 MPH or would he be tossed and spun around while flying?

I imagine the air in the tires moves mostly with the tire, but it probably takes a little longer to get up to speed, especially if the car accelerates quickly.

a reply to: Aldakoopa

I would think so too but it`s the spinning while moving forward that has me baffled.

I guess it`s a lot like the air inside your car when you are travelling at 60 MPH,the flies in your car can fly around inside the car just fine.

I think the air in the tire is moving forward at 60 MPH,just as the air in your spare tire that is in your trunk is moving forward at 60 MPH (I think) but then you ad the rotation of the tire as it`s moving forward at 60 MPH and I`m lost.

This is probably more of a physics question, I suppose.

The reason I started thinking about this is because I had to put a rubber plug in one of my tires that got a small puncture. the plug was about 3-4 inches long and most of the plug ends up inside the tire with just about a 1/4 inch outside the tire.
so, I guess the air pressure in the tire forces the plug up against the inside of the tire and the inside of the hole.

of course there is the whole issue of the air in the tire being compressed to 32 PSI.

That`s what got me thinking about what the air inside the tire is doing while the wheel is spinning around.

a reply to: Tardacus

Came into this one thinking I'd likely know the answer, but I don't believe I have witnessed that principle in motion. I'd imagine the air molecules are suspended in air like everywhere else, until the air is forced to react to the inertia of hitting the underside of the tire treads. Because its round and traveling forward... the air molecules would likely have the illusion of spinning backwards initially, but turn into a vortex soon thereafter.

As the tires drive on, they heat up a bit and the air molecules expand... causing the pressure inside the tire to increase. I am assuming that a lot of that pressure/heat increase is due to sir interacting air molecules as the tire throws them around like bingo balls.

a reply to: Tardacus

I guess it`s a lot like the air inside your car when you are travelling at 60 MPH,the flies in your car can fly around inside the car just fine.

Nope... can't compare the 2! If the headliner and floorboard were rotating at 60 MPH around us, then yes... you can compare the 2. If they were similar, and the fly lands on the headliner or floor, its going to get beat to hell if its the same as inside a tire... it would be like stepping on a treadmill when its already going full speed... hahaha.

Well, there is only one way to find out for sure. Someone is going to have to fill their tires with flies. Like a real scientist.

a reply to: Tardacus

a reply to: Woodcarver

yeah, a clear plastic or clear rubber tire so you can see what`s happening to the flies inside the tire as it spins.

there`s just so much going on in there to consider,
there`s the pressurized air
there`s the centrifugal force
there`s the relatively smooth inside of the tire
there`s the forward motion of the tire
there`s the up and down motion of the tire
there`s the rotation of the tire

I`m not familiar with how much friction there is between air molecules,the pressure is forcing some of the air molecules to stay in contact with the inside of the tire so those molecules have to be spinning pretty fast, and the pressure is compacting all the molecules pretty tight together, I imagine,so maybe they all are spinning.

a reply to: ttobban

yeah, I`m not sure there are any principles that would fit this situation,because of all the different factors it doesn`t exactly fit hydraulic or pneumatic principles.

a reply to: Tardacus

Well, think about it. If the air in the tires heats up and expands as we drive, friction between air molecules is the only explanation for that. This does not occur in your spare tire as you drive, because its similar to being a passenger in a car.

A fly is not expected to live if inside a tire... unless it can somehow magically avoid touching any or the rotating surfaces within. Not to mention it would have to fight the vortexes of the air molecules meshing too... forces that are both centrifugal and centripetal.

We use air in tires as compared to hydraulics for the simple fact that air molecules are able to be compressed... fluid filled tires would suck. The oxygen molecules are able to be altered over the course of the heat changes and vortexes within. That's why there is a big sell on Nitrogen in tires... because Nitrogen molecules are more stable, and don't react to heat and friction quite like air. It's a con upsell for your tires too... because air already is 87% nitrogen.

a reply to: Tardacus
Does this satisfy you question?

www.physicsforums.com...

Aug 4, 2004 #10 ArmoSkater87

Reference www.physicsforums.com...
There are several factors involved in this situation...so its hard to tell now. You have bernouli affects, centripital acceleration, friction against the ground. Lets think about this, the car is moving, since air has very little friction, it takes a long time for it to start circulating. When it circulates, you have the air pressure drop from bernouli affects. The centripital force makes the air molecules pile up on the bottom of the tire, therefore, having a higher pressure. The friction of the tire against the ground heats up the rubber, but i think we can rule this one out because rubber is a bad thermal conductor. But there is another source of friction, which is the friction of the air against the bottom and sides of the tire (more against the botton since thats the area of higher pressure). SO, now we have higher pressure and temperature at the bottom of the tire, while a little lower pressure towars the center, but at the same time we have all this air circulating, which causes the overall pressure to go down (this is alll while the car is in motion). So, when the car slows down and stops, the air takes a little while to stop circulating (which makes it increase in pressure) because of the small amount of friction it has. At the same time you have the air (hot in the biginning) cooling down slowly, which causes a decrease in pressure. From my understanding of it, there is an equilibrium effect going on here. I dont think you can qualitatively conclude whether it will increase or decrease in pressure. Reference www.physicsforums.com...

a reply to: Tardacus

Coriolis effect???

a reply to: Tardacus

Gas molecules (air is gases) are in constant, chaotic motion all the time. We call this Brownian motion.

When the tyre starts to roll, inertia will see to it that a little time passes before its motion is transferred to the air molecules inside.

Here is the way it happens. Gas molecules in Brownian motion collide with the tyre wall and bounce off. They receive an acceleration in the direction that part of the tyre wall is moving. On the rebound, these molecules collide with others amd transfer some of their momentum to them. Slowly the whole mass of air begins to move.

But since the tyre is rotating around an axis that is itself in linear motion, air molecules continue to collide with the tyre wall and be deflected until the whole mass of air inside the tyre has an average motion that replicates that of the tyre itself.

However, the motion of individual gas molecules in the mass will continue to be random and Brownian.

Finally, although the mass of gas in the tyre is all at one pressure if you measure it when the tyre is stationary, in motion a pressure differential will develop between the inner (nearest the wheel rim) and outer (nearest the tread) sides of the tyre due to centrifugal effect. The pressure will be highest nearest the tread.

a reply to: Tardacus

The air expands as the friction of the road heats it up... it isn't healthy to jog/run near roadways either as there is a lot of pollution from vehicle waste in the form of oils, debris and exhaust carbon all over everything... aside from the chances of being hit by a passing vehicle as well.

It's a good question. I would say initially it doesn't all turn, it remains neutral but sooner or later forms a sort of vorte pattern. If you put water in a bowl, then spin the bowl, the water only slowly starts to rotate. I assume it would be similar for air but can't be totally sure.

I would say it would not be different than if you had liquid in a cup and began to spin the cup. The liquid near the sides would move with the cup while the stuff in the middle less so. Maybe then after a while all of it will be spinning.

The tire is going to act as a low speed centrifuge.

Air is a gas- in a question of how a gas might act in a given situation, think of it as a liquid. A really light one.

The rotating walls of the tire will grab some air molecules and throw them in that direction. Those molecules will hit others, and disperse their energy into them.
All of these molecules will find themselves trying to hug the outer tire wall.
The air does move with the tire

I'd try to find a video of smoke or dust in a centrifuge.

edit:
this isn't a half bad demonstration, but with dirty veggie oil.
www.youtube.com...

Yes , it does move
Look at it at a simple level. Ever had the tire pressure light on a tire(s) come on just cause it is cold ? Now , after traveling and the air heats up , the light(s) go off...
Physics....

a reply to: lordcomac

What ^^^ this guy ^^^ said.

Your fly will also smack to the side of the tire wall and spin with it. If you had 1000 flies, they would be smacked to the side of the tire wall in all directions, spinning with it. If the car moves forward, and the fly is flying in place, he will make contact with the wheel wall. Once the tire starts moving at any certain speed, it'll be toss up against that rubber wall and stay there till the forward motion slows enough for him to fall.

Gravity and Motion all apply here.

a reply to: StallionDuck

Sorry, that is not correct.

As I stated earlier, individual molecules are in constant motion. They do not 'stay there till the forward motion slows enough for [them] to fall.'

a reply to: Astyanax

I dont believe you.

Every been to the fair and rode the gravitron?