I survived, but now some questions remain

[straatvark]

haha best topic for the day.

 

There is always going to be a last nut that break, not all at once. (Even only for every short time) That means the very last moment before the wheel came 100% free moving, the torque transfer to the wheel (or FROM the wheel for front wheel) is off - center via that last nut/stub. So the wheel are "shot" away with a slingshot action, also causing the jumps etc.

 

That is my "gorrel" for points in last 10 minutes of mechanics 202   

[Veloce]

 

 

nope... the surface in contact with the road is travelling @ 120km/h...

 

Funny enough' date=' the surface in contact with the road is travelling at Zero kph with respect to the road.

 

On a moving tank or bulldozer, approximately one third of the track is always stationary with respect to to the ground it is moving over.

 

 

[/quote']

 

Not funny at all. The bottom most part of the tyre is travelling a t 0 km/h and the top most part is travelling at 240 km/h for a vehicle travelling at 120km/h. The only time the bottom most part of the tyre is travelling at more than 0 km/h is when there is wheelspin.

 

As for the record player story, the outside is travelling faster than the inside, if you make 2 marks on the record, one near the center and one one the outermost part, the one in the center has trevelled less distance in the same amount of time, therefore it has travelled slower. The data on the record is just "stretched" as you move outwards.

 

As for the wheel, I'm not going with the increase in diameter theory as it would indeed travel faster than a smaller diameter wheel with the same amount of revolutions however more energy would be required in order to achieve this. Hmmmmmmmmmmm...

  

[Wazza]

 

 

nope... the surface in contact with the road is travelling @ 120km/h...

 

Funny enough' date=' the surface in contact with the road is travelling at Zero kph with respect to the road.

 

On a moving tank or bulldozer, approximately one third of the track is always stationary with respect to to the ground it is moving over.

 

 

[/quote']

 

Not funny at all. The bottom most part of the tyre is travelling a t 0 km/h and the top most part is travelling at 240 km/h for a vehicle travelling at 120km/h. The only time the bottom most part of the tyre is travelling at more than 0 km/h is when there is wheelspin.

 

As for the record player story, the outside is travelling faster than the inside, if you make 2 marks on the record, one near the center and one one the outermost part, the one in the center has trevelled less distance in the same amount of time, therefore it has travelled slower. The data on the record is just "stretched" as you move outwards.

 

As for the wheel, I'm not going with the increase in diameter theory as it would indeed travel faster than a smaller diameter wheel with the same amount of revolutions however more energy would be required in order to achieve this. Hmmmmmmmmmmm...

  

 

Thanks Veloce, That's what I was trying to tell these okes.

[TNT1]

 

 

Thanks Veloce' date=' That's what I was trying to tell these okes.

[/quote']

 

And I'm trying to tell them that I'm going home, dropping acid, listening to Grand Funk Railroad backwards for hidden messages regarding the theory of time dilation derived from the special theory of relativity, and then I'm installing a new cateye on my bike.

 

[Reg Lizard]

My brother in law once told me that they were driving from a spot at Kommetjie where they were diving when the rear wheel of his Baja Bug also came rolling past them.  (Oh sit here comes a wheel, oh wait, its my wheel).He stopped and the passenger had to run a couple of hundred metres after it. Apparently while they were diving someone tried to steal the wheel, but before they could, he returned. All the nuts were removed, so he took a nut from each of the remaining three wheels to tighten the wheel again and drove home.

[greatwhite]

Ok heres my take on this. It has to do with relativity.

 

......

 

Now because the wheel was heading toward your friend while the truck was actually heading off at a tangent' date=' it would be perceived that the wheel was accelerating toward the driver while the truck wasn't. It's a matter of where you are observing the event from. If you were sitting in the truck you would see the wheel separate, run alongside and then gradually drop back as it's distance to the truck grows while it is heading tangentially away from the vehicle.

[/quote']

 

Ditto, thats my take too.

 

 

As for the wheel' date=' I'm not going with the increase in diameter theory as it would indeed travel faster than a smaller diameter wheel with the same amount of revolutions however more energy would be required in order to achieve this. Hmmmmmmmmmmm...

  

[/quote']

 

I don't buy it either, also the change of diamater is minimal at best.

 

Some simple observations and a question:

Things don't go faster when no energy is added (the wheel)

Things do go slower when more energy is required, but not provided (the truck)

Was the AWOL wheel a driving or driven wheel? (most are driven and are being 'dragged' along with nothing to add energy even before departing the truck)

 

On a 'lighter' note:

JB: was the taxi wheel was a friendly warning preceeding the real onslaught?

If so, I've had my warning - a taxi coming the other direction did a rather prompt and unplanned U turn in front of me when his front wheel decided to part ways - the wheel just missed me but caused havoc in the intersection I'd just come through. I've also witnessed 2 others that have had their 'warning' roll unexpectedly out from under a taxi.

I just hope its not truck wheels for me next as well.....

 

I wonder whether trucks or taxis loose wheels more often?

 

 

[greatwhite]

Ok heres my take on this. It has to do with relativity.

 

......

 

Now because the wheel was heading toward your friend while the truck was actually heading off at a tangent' date=' it would be perceived that the wheel was accelerating toward the driver while the truck wasn't. It's a matter of where you are observing the event from. If you were sitting in the truck you would see the wheel separate, run alongside and then gradually drop back as it's distance to the truck grows while it is heading tangentially away from the vehicle.

[/quote']

 

Ditto, thats my take too.

 

 

As for the wheel' date=' I'm not going with the increase in diameter theory as it would indeed travel faster than a smaller diameter wheel with the same amount of revolutions however more energy would be required in order to achieve this. Hmmmmmmmmmmm...

  

[/quote']

 

I don't buy it either, also the change of diamater is minimal at best.

 

Some simple observations and a question:

Things don't go faster when no energy is added (the wheel)

Things do go slower when more energy is required, but not provided (the truck)

Was the AWOL wheel a driving or driven wheel? (most are driven and are being 'dragged' along with nothing to add energy even before departing the truck)

 

On a 'lighter' note:

JB: was the taxi wheel was a friendly warning preceeding the real onslaught?

If so, I've had my warning - a taxi coming the other direction did a rather prompt and unplanned U turn in front of me when his front wheel decided to part ways - the wheel just missed me but caused havoc in the intersection I'd just come through. I've also witnessed 2 others that have had their 'warning' roll unexpectedly out from under a taxi.

I just hope its not truck wheels for me next as well.....

 

I wonder whether trucks or taxis loose wheels more often?

 

 

[Johan Bornman]

Some more clues:

 

1) There was no precession in any of the three cases I observed. The wheel rolled perfectly straight and didn't do a top-like wobble.

2) Any bouncing was merely to do with pavements, Unos and small children that got int the wheel's way.

3) There wasn't a Ford Siera to be seen anywhere.

4) The wheel DEFINITELY overtook the truck which DEFINITELY didn't have a clue that it just launched a wheel and therefore PROBABLY didn't slow down.

 

 

 

[GoLefty!!]

Johan the wheel can precess in two planes. It's own vertical plane which would be the wobble or around a virtual point at the centre of the arc that it would describe if it could run on forever.

 

Think the earth orbiting the sun while still wobbling.

 

If the wheel overtook then the truck slowed but or it too accelerate it would require additional energy or force to make it accelerate. No mass was added and no additional force could be introduced unless there was a small bloke from Benoni giving it a kick every now and then.

 

I have seen this on race cars as well, even go-karts. Some poephol forgets to tighten the frikken wheel nut properly, the wheel comes off and the wheel overtakes the car / kart because the car / kart has slowed down.

[GoLefty!!]

Johan the wheel can precess in two planes. It's own vertical plane which would be the wobble or around a virtual point at the centre of the arc that it would describe if it could run on forever.

 

Think the earth orbiting the sun while still wobbling.

 

If the wheel overtook then the truck slowed but or it too accelerate it would require additional energy or force to make it accelerate. No mass was added and no additional force could be introduced unless there was a small bloke from Benoni giving it a kick every now and then.

 

I have seen this on race cars as well, even go-karts. Some poephol forgets to tighten the frikken wheel nut properly, the wheel comes off and the wheel overtakes the car / kart because the car / kart has slowed down.

[Johan Bornman]

 

Cut cut cut

 

 

I don't buy it either' date=' also the change of diamater is minimal at best.

 

Some simple observations and a question:

Things don't go faster when no energy is added (the wheel)

Things do go slower when more energy is required, but not provided (the truck)

Was the AWOL wheel a driving or driven wheel? (most are driven and are being 'dragged' along with nothing to add energy even before departing the truck)

 

 

[/quote']

 

No energy was added to the wheel, but at the moment of departure, none removed either. But some resistive forces were removed, yet the kinetic energy remained the same - therefore the wheel accellerated.

 

In other words, they do go faster if the balance of force is altered in favour of the wheel.

 

Lefty, I hear your carting argument but this is not a four-wheel vehicle but a truck to whom one more or less wheels doesn't matter. I don't think the overall rolling resistance increases with one wheel less.

 

GW, I don't think driving or driven has bearing here at all. It could have been a powered axle or (whatever a non-powered axle is called) one. At the moment of separation it is a free body and no driving force is applied and it only posesses kinetic energy that's sapped by wind resistance, gradient, and hysteris in the tyre.

 

I also don't like Straatvark's slingshot idea - sorry Varkie.

 

Nick and Bruce have the answers guys.

 

Anyway, I'm leaving you all for three days. Please sort this out amongst yourselves and don't screw the physics.

 

Nick, please mark all submissions and have a summary in my Inbox on Monday.

[Guest Big H]

Johan, another teaser I have never found an answer to.

 

A truck that weighs 5 tons loaded with chickens need to cross a bridge that can only carry 4 tons. The chickens weigh 1,5 tons in total. If the truck crosses the bridge and I slam on the sides to let two thirds of the chickens fly, will the truck be light enough to cross the bridge????????

[fandacious]

Johan' date=' another teaser I have never found an answer to.

 

A truck that weighs 5 tons loaded with chickens need to cross a bridge that can only carry 4 tons. The chickens weigh 1,5 tons in total. If the truck crosses the bridge and I slam on the sides to let two thirds of the chickens fly, will the truck be light enough to cross the bridge????????

[/quote']

 

no, because the downforce generated by the flying chickens is at least equal to their mass.

[Mudsimus]

And mythbusters proved it!

[hot stuff]

I was taking my trailer to the dump with horse manure and this was very heavy. My 2 grooms neglected to hitch it properly, I neglected to check. Came down my steep hill , no problem, turned into ladies mile and the next thing the trailer was overtaking me on the left, and then crashed. i shudder to think what would have happened if there were pedestrians on the pavement. And as it turned out, a couple of kids arrived on the scene a couple of seconds later totally oblivious of what had just happened. had they arrived earlier, i am sure i would be locked up by now

[fandacious]

And mythbusters proved it!

 

i never saw that one... but i dunno why you would have to prove it...

 

its pretty simple logic. if you have 5.5tonnes of mass, you cant magically make some of it dissappear. "for every action there is an equal and opposite reaction". So if the birds are up in the air, they have to be exerting a downwards pressure.