I survived, but now some questions remain

[bruce]

Friction forces do play a role since friction force is the ReactionForce N x coefficient of friction' date=' which is a constant for the road and tyre interface. What changes is N.

Drag increases sinces the wheel is now exposed to the whole airflow.

 

no other forces are added or deducted from the system.

But since the friction force is so small anyway in relation to the inertia It does not play a role in providing a sustained acceleration, in fact since the drive forces are removed the wheel will deccelereate almost immediately after departure. It's like a bullet out of a rifle barrel. All the acceleration happens will the slug is propelled by the shock wave of expanding gas behind it. One it leaves the barrel (wheel leaving the axle) it decellerates constantly due to friction and air resistance. Same counts for the wheel.

 

Any perceived acceleration of the wheel by an observer standing in the way is due to

panic

wetting their pants

Pooing themselves

optical illusion due to position of observer.

[/quote']

 

Disagree.

 

A wheel spinning at 100rpm has potential energy due to rotation:

 

E = 1/2 x I x w^2

 

Whether it is attached to a vehicle or not.

 

When it is attached to a vehicle, it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

 

[Capri Wheeler]

A cowboy named Mzokoto was overseeing his herd in a remote

mountainous pasture in Mphompha when suddenly a brand-new BMW 6 Series Coupe

advanced out of a dust cloud towards him. The driver, a young man in a Brioni

suit, Gucci shoes, RayBan sunglasses and YSL tie, leans out of the window and

says to the cowboy,

 

"If I tell you exactly how many cows and calves you

have in your herd, will you give me a calf?"

 

Mzokoto looks at the man,

obviously a yuppie, then looks at his peacefully grazing herd and calmly

answers, "Sure. Why not?"

 

The yuppie parks his car, whips out his Dell

notebook computer, connects it to his Cingular RAZR V3 cell phone, and surfs to

a NASA page on the Internet, where he calls up a GPS satellite to get an exact

fix on his location.  He feeds this to another NASA satellite that scans the

area in an ultra-high-resolution photo. The young man then opens the digital

photo in Adobe Photoshop and exports it to an image processing facility in

Hamburg, Germany. Within seconds, he receives an email on his Palm Pilot that

the image has been processed and the data stored. He then accesses an MS-SQL

database through an ODBC connected Excel spreadsheet with email on his

Blackberry and, after a few minutes, receives a response. Finally, he prints out

a full-color, 150-page report on his hi-Tech Miniaturized HP LaserJet printer

and turns to the cowboy and says, "You have exactly 1,586 cows and

calves."

 

"That's right,"  says Mzokoto. "Well, I guess you can take one

of my calves."

 

He watches the young man select one of the animals, and

looks on amused as the young man stuffs it into the trunk of his car.

 

 

Then Mzokoto says to the young man, "Hey, if I can tell you exactly

what your business is, will you give me back my calf?"

 

The young man

thinks about it for a second and then says, "Okay, why not?"

 

"You're an

IT Consultant", says Mzokoto.

 

"Wow! That's correct," says the yuppie,

"but how did you guess that?"

 

"No guessing required," answered the

cowboy.

 

"You showed up here even though nobody called you; you wanted

to get paid for an answer I already knew, to a question I never asked. You tried

to show me how much smarter than me you are; and you don't know a thing about

cows...this is a herd of sheep. . ...Now give me back my dog."

[GoLefty!!]

Friction forces do play a role since friction force is the ReactionForce N x coefficient of friction' date=' which is a constant for the road and tyre interface. What changes is N.

Drag increases sinces the wheel is now exposed to the whole airflow.

 

no other forces are added or deducted from the system.

But since the friction force is so small anyway in relation to the inertia It does not play a role in providing a sustained acceleration, in fact since the drive forces are removed the wheel will deccelereate almost immediately after departure. It's like a bullet out of a rifle barrel. All the acceleration happens will the slug is propelled by the shock wave of expanding gas behind it. One it leaves the barrel (wheel leaving the axle) it decellerates constantly due to friction and air resistance. Same counts for the wheel.

 

Any perceived acceleration of the wheel by an observer standing in the way is due to

panic

wetting their pants

Pooing themselves

optical illusion due to position of observer.

[/quote']

 

Disagree.

 

A wheel spinning at 100rpm has potential energy due to rotation:

 

E = 1/2 x I x w^2

 

Whether it is attached to a vehicle or not.

 

When it is attached to a vehicle, it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

 

 

ok that makes sense

[Veloce]

Friction forces do play a role since friction force is the ReactionForce N x coefficient of friction' date=' which is a constant for the road and tyre interface. What changes is N.

Drag increases sinces the wheel is now exposed to the whole airflow.

 

no other forces are added or deducted from the system.

But since the friction force is so small anyway in relation to the inertia It does not play a role in providing a sustained acceleration, in fact since the drive forces are removed the wheel will deccelereate almost immediately after departure. It's like a bullet out of a rifle barrel. All the acceleration happens will the slug is propelled by the shock wave of expanding gas behind it. One it leaves the barrel (wheel leaving the axle) it decellerates constantly due to friction and air resistance. Same counts for the wheel.

 

Any perceived acceleration of the wheel by an observer standing in the way is due to

panic

wetting their pants

Pooing themselves

optical illusion due to position of observer.

[/quote']

 

Disagree.

 

A wheel spinning at 100rpm has potential energy due to rotation:

 

E = 1/2 x I x w^2

 

Whether it is attached to a vehicle or not.

 

When it is attached to a vehicle, it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

 

 

YES!!! This makes perfect sense!! My concentric shaft story only modelled the wheel on its own. Having the mass of the vehicle in which th energy is unloaded, and the removal thereof (energy not being created or destroyed) the wheel can only accellerate.   

[GoLefty!!]

yep, Been in marketing too long. Failed to see the vehicle as the energy sink. [slaps forehead, and heads off to self flaggulation]

[parabola]

 

Disagree.

 

A wheel spinning at 100rpm has potential energy due to rotation:

 

E = 1/2 x I x w^2

 

Whether it is attached to a vehicle or not.

 

When it is attached to a vehicle' date=' it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

[/quote']

 

Agreed. I've thinking about this since it was posted, and this theory best explains it. Some smart okes around these parts .

 

[JPW#]

maybe one of the questions that remain is, is God trying to tell me something? Like eg. Even tho I know E=Mc2 I still need He's protection just to survive 1 single day.)

 

 

[Guest Big H]

maybe one of the questions that remain is' date=' is God trying to tell me something? Like eg. Even tho I know E=Mc2 I still need He's protection just to survive 1 single day.)

[/quote']

 

Your formula is wrong...... it has since changed to E=Mc3 ....... due to the R/$ exchange rate, inflation and price fixing!!!!!!!!

[JPW#]

It might change to E=Mc4 in the future due to the R/Zim$ exchange rates.)

[latentree]

 

 Disagree.

 

 A wheel spinning at 100rpm has potential energy due to rotation:

 

 E = 1/2 x I x w^2

 

 Whether it is attached to a vehicle or not.

 

 When it is attached to a vehicle' date=' it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

 

[/quote']

E = 1/2 x I x w^2, that's kinetic energy. When the wheel is detached there is nothing that can exert a force on it to go faster. It gets slowed down by bit of friction & mostly air resistance.

I think the acceleration just after release is due to bigger radius (centre of wheel to road surface distance)  with the load on it now removed, but the immediate rpm same as just prior to release.

 

 

Retention of angular momentum will cause some loss of rpm on release of wheel, but that's dependant on the mass moving away from centre of rotation, which is just the piece of tire previously "flat" on the road & now same r as rest. (outstreched arms vs. tucked in while spinning on chair effect, but here maybe same as fist vs. open hand) This seems to be offset by above mentioned.

 

That's what i fink anyhow.

 

 

[bruce]

 Disagree.

 A wheel spinning at 100rpm has potential energy due to rotation:

 E = 1/2 x I x w^2

 Whether it is attached to a vehicle or not.

 When it is attached to a vehicle' date=' it unloads this energy into the mass of the vehicle - which will absorb far greater amount of this energy and resist the forward motion of the wheel.

 

When it becomes detached, the only forces that it can unload this stored energy into are rolling resistance and wind resistance - far less combined force than the force opposing the attached wheel.

 

Force imbalance occurs and nett forward force on the wheel becomes positive, causing the wheel to accelerate until increased forces due to wind and rolling resistance bleed enough of this energy for the forces to become balanced again.

 

[/quote']
E = 1/2 x I x w^2, that's kinetic energy. When the wheel is detached there is nothing that can exert a force on it to go faster. It gets slowed down by bit of friction & mostly air resistance.
I think the acceleration just after release is due to bigger radius (centre of wheel to road surface distance)  with the load on it now removed, but the immediate rpm same as just prior to release.


Retention of angular momentum will cause some loss of rpm on release of wheel, but that's dependant on the mass moving away from centre of rotation, which is just the piece of tire previously "flat" on the road & now same r as rest. (outstreched arms vs. tucked in while spinning on chair effect, but here maybe same as fist vs. open hand) This seems to be offset by above mentioned.

That's what i fink anyhow.

 

Sorry, my bad, energy stored in the wheel is a sum of the 2 types of kinetic energy rotational = (1/2 x I x w^2) plus forward motion = (1/2 x m x v^2)

 

I used the term potential energy because I was talking about stored energy.  That stored energy must be released, and when the wheel is set free, it is released into rolling and wind resistance.

 

 

bruce2008-11-13 04:55:23

[Mudsimus]

I think this explains why the wheel is going faster.

 

 f(x) = a1 / ( p1*exp{x*c1} + b1 ) - (p_i*x'^c_i + b_i)+ a2 / ( p2*exp{x*c2} + b2 ) + ... + a10 / ( p10*exp{x*c10} + b10 ) - (m) = wheel going faster.

[greatwhite]

I think this explains why the wheel is going faster.

 

 f(x) = a1 / ( p1*exp{x*c1} + b1 ) - (p_i*x'^c_i + b_i)+ a2 / ( p2*exp{x*c2} + b2 ) + ... + a10 / ( p10*exp{x*c10} + b10 ) - (m) = wheel going faster.

 

Whos maths book did you steal?

 

Try some easier calculation 1st:

1 Taxi + 4 wheels = Happy JB

1 Taxi + 3 wheels = Nervous JB

[davetapson]

From my boet, the physics prof:

 

I reckon the key is to understand the effect of the flat contact spot where the tyre touches the road.  The flatness effectively reduces the wheel's radius, but only at that one point in the tyre.  So, when the wheel detaches, its radius increases (effectively, no weight on it, so no flat spot, so the effective radius is larger).  But the wheel's mass distribution stays the same, so the angular momentum stays the same, so the spinning rate stays the same.  Same spinning rate x wider radius = goes faster.  If the increase in radius was accompanied by a corresponding outward movement of mass, the wheel would slow down (like a pirouetting ice skater extending her arms).  The only outward movement is at the flat spot, which is a negligible change in mass distribution, but because all the road contact is through the flat spot, the effective radius of the whole tyre changes. 

Will provide mathmatical proof for beer.

 

[Christie]

1. I dont like the truk absorbing energy from the wheel idea. I would think it would be the other way around - engine imparts energy to truck & drive wheels, truck gives energy to non-drive wheels.

 

2. I dont think the change in radius theory is good, either, because the effective change in radius will be very small.

 

Im sticking with change in rolling resistance.

[Johan Bornman]

The only extra "energy I think thay can aslo have an effect to the wheel accelerating is that the wheel is pumped a certain pressure. with the weight of the truck pressing down with force and the tire pressing back( one of newtons laws. Now as soon as the tire dislodges it "Pops" the wheel faster. Like pressing somthing hard between two fingers and it ops out.

cUT CUT CUT

 

 

 

The effect you describe would indeed return some energy to the system but it's direction would be upwards and not forwards.

 

The little hop this sudden release of weight on the wheel can easily be determined with a little experiment.

 

Hold the wheel at X height above the ground. Drop it and note the highest point it bounces up to. This is Y. (Y is always smaller than X).

 

The loss in rebound (equal to the hysteresis in the rubber) would be X minus Y. This distance would also be the little bounce the wheel would receive on initial release as the wheel breaks off the axle.

 

But like I said, this would be vertical and not forward and therefore contribute nothing to its forward accelleration.

 

This experiment also gives you a relative idea of how much rolling resistance your tyre has at a given tyre pressure. Simply drop the wheel and see how high it bounces. The smaller the loss, the smaller the rolling resistance.

 

This is because in tubular shaped tyres such as bicycle tyres, there is very little frictional force by way of tyre scrub present and most of the energy is simply lost in the rubber itself.

 

On the truck tyre is is considerable scrub and some is lost to friction as the tyre expands it footprint under pressure, which is seen as a rubbing or scrubbing force between rubber and road.

 

In an underground car park with a smooth floor this is audible by way of tyre squeal.