I survived, but now some questions remain

[madmarc]

i would assume that a wheel is like a flywheel, it stores a lot of potential energy but is governed by the fact that it is connected to the axle. But when it is suddenly released ther is no governer so the stored energy is released causing it to accelerate. also bieng inflated and hitting objects will cause a sudden increae in potential energy causing it to accelerate even more or in most cases bounce around.

[Bateleur1]

 

He he...funny. However' date=' the drivers don't even know a wheel has broken off. 

 

[/quote']

 

Does not surprise me especially if it involves a trailer.  I was towing a trailer on my way back from the Amashova last year.  30 odd kilos from Harrismith I was traveling at 130 km/h.  All of a sudden I heard a funny noise and for about 2 seconds I felt something dragging the car and then it all stopped and the car was travelling normal.  Still puzzled I looked in my rear view mirror again and noticed the trailer is sligthly lower on the one side and then also a big piece of tyre flying into the veldt.  The hub did not drag on the tar at all.

[Johan Bornman]

yo!!!! JB!!!! please confirmt hat you were using a hands free kit!!!!!

 

The only confirmation I can make in the said case is that the driver's seat is now clean and safe to sit on again.

[Bateleur1]

yo!!!! JB!!!! please confirmt hat you were using a hands free kit!!!!!

 

The only confirmation I can make in the said case is that the driver's seat is now clean and safe to sit on again.

 

No bite marks?

[Speed Devil]

JB, Luckily I have not had any of this happen to me but have witnessed it once before....the wheel coming off and overtaking the vehicle. All explanations above are technically correct, although no scientific calculations/explanetions have been given.

Madmarc's explanation is correct, but don't forget that besides the applied force by the axle, once the wheel leaves the vehicle, the rotational inertia will also help speed up the wheel seeing as it is much lighter than the vehicle that it came off.

Once it starts bouncing it's momentum will also increase, as their is less resistance in air than when it simply just rolls along the tar.

[Mudsimus]

If a Sierra's exhaust moers off right in front of you it does not travel faster than the Sierra but slams into you're car.

[Christie]

I would also go for the change in rolling resistance theory.

 

When it comes loose, there is a whole lot less downward force on the wheel, meaning the rolling resistance will reduce significantly when it gets unloaded. The moment it breaks loose, it will still having the same kinetic energy, so it will accelerate till the balance of forces is restored.  

[Speed Devil]

If a Sierra's exhaust moers off right in front of you it does not travel faster than the Sierra but slams into you're car.

 

That's because the forces created by gases coming out the outlet manifold blasts it off the back of the car....similar to what happens to humans (the only difference is that our exhaust stays intact)

[Johan Bornman]

If a Sierra's exhaust moers off right in front of you it does not travel faster than the Sierra but slams into you're car.

 

My sense of perceptions is hightened this morning by the fact that the coffee beans are finito.

 

I therefore read between the lines that you have prove the above statement and feel so strongly about your belief that you are not going to back it up with formulas and hypotheses?

[Johan Bornman]

JB' date=' Luckily I have not had any of this happen to me but have witnessed it once before....the wheel coming off and overtaking the vehicle. All explanations above are technically correct, although no scientific calculations/explanetions have been given.

Madmarc's explanation is correct, but don't forget that besides the applied force by the axle, once the wheel leaves the vehicle, the rotational inertia will also help speed up the wheel seeing as it is much lighter than the vehicle that it came off.

Once it starts bouncing it's momentum will also increase, as their is less resistance in air than when it simply just rolls along the tar.

[/quote']

 

I disagree, I think most explanations are technically incorrect. Madmarc confuses potential and kinetic energy and suddenly adds a dose of potential energy just because the wheel strikes a rock.

 

 

[Speed Devil]

JB' date=' Luckily I have not had any of this happen to me but have witnessed it once before....the wheel coming off and overtaking the vehicle. All explanations above are technically correct, although no scientific calculations/explanetions have been given.

Madmarc's explanation is correct, but don't forget that besides the applied force by the axle, once the wheel leaves the vehicle, the rotational inertia will also help speed up the wheel seeing as it is much lighter than the vehicle that it came off.

Once it starts bouncing it's momentum will also increase, as their is less resistance in air than when it simply just rolls along the tar.

[/quote']

 

I disagree, I think most explanations are technically incorrect. Madmarc confuses potential and kinetic energy and suddenly adds a dose of potential energy just because the wheel strikes a rock.

 

 

 

I was refering to the bit about the wheel being held back by the axle and then accelarating after breaking loose.

[NickD]

Hi Johan,

Just too pleased that you are ok!

Without quoting formulas ( cant use eq. editor in here and just too lazy to type separate text and paste) just consider the wheel as a free body.

With the vehicle travelling at a constant speed the wheel has the following forces applied to it:

A driving force at the hub which is in equilibrium with the friction times the vertical reaction acting at the contact point. Effectively both forces are removed when the wheel leaves the axle. However, because the wheel is turning it has an amount of  kinetic energy stored which is a function of the mass of the wheel and the angular velocity. The problem is therefore the same as spinning up the wheel in a stationary position and releasing it. Think what would happen if the wheel had no mass?

On the subject of linear momentum, a story I heard many years ago when the Rhodesian bush war was still on: A senior citizen converted an old Peugot station wagon to a gunbus by adding a machine gun to fire through the grill. Then, deciding that the rear was vulnerable, he installed a chute ( probably a piece of water pipe from the front to the rear so that he could chuck a hand grenade down it while driving.

The vehicle did not survive the test run. Why?

Regards and glad you are ok.

Nick

[Shebeen]

i went riding yesterday in cape town and a crumpled coke can overtook me. beat that

[nellie]

okay...too lazy too read through the rest, so if someone's said this already...bite me!

 

Krag toegepas = massa van voorwerp x voorwerp se versnelling

 

gemanupileer:

voorwerp se versnelling = krag toegepas / massa

 

dus - direk nadat die wiel losgekom het van die trok het hy nog dieselfde aantal krag besit (al is dit net vir 'n paar sekondes)

Wiel is baie ligter as die trok so, dit sal oorspronklik vinniger beweeg  (bv 1000N / 10 000kg teenoor 1000N / 50kg)

 

la die da...skryf Vrydag Skeinat...

[nellie]

Anyhow...flip...ons het al op die fietse gery en 'n trok se band het gebars net so 50m voor ons!! SCARY!!! het amper myself natgemaak toe ek daai geluid hoor!

[Rakker]

I also witnessed this and yes, that was one fast wheel! Luckily for me I kept to the speed limit (would have been next to the car if I hadn't) and the wheel missed my car. Just my luck.