I survived, but now some questions remain

[Matchstix]

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.

 

I lost my own car wheel 2 days before I had to drive to PTA. Turns out two wheelnuts were stripped and only two holding the wheel on. that was one advantage of reckles teenage driving.

Nellie goodluck with the xam sounds like youre gonna ace it.

 

[Guest Big H]

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' date=' 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.

[/quote']

 

And if the truck has mesh or grid sides where the "wind" or downward thrust can escape????? Have you ever measured the mass of a bird in flight???????

[Guest Big H]

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' date=' 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.

[/quote']

 

Your signature of the whales makede me think of a bumper sticker I once saw....."F..k the whales ...... harpoon a fat chick"!!!!!!!!

[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' date=' 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.

[/quote']

 

And if the truck has mesh or grid sides where the "wind" or downward thrust can escape????? Have you ever measured the mass of a bird in flight???????

 

why would i want to measure its mass while in flight? its mass stays the same, regardles of whether or not its flying. If its mass is 25N, then it must exert a downward force of more than 25N to get it up in the air.

[Mudsimus]

But chickens cant fly...

[fandacious]

But chickens cant fly...

 

http://www.binghamton.edu/calendar/nov-dec/24nov05ask.html

[Mudsimus]

I grew up on a farm and never saw one chicken fly. They can run in circles with their heads cut of though.

[fandacious]

I grew up on a farm and never saw one chicken fly. They can run in circles with their heads cut of though.

 

you never threw them high enough

 

try this - http://en.wikipedia.org/wiki/Chicken_Cannon

[Guest Big H]

But chickens cant fly...

 

....... because there are no trees in the Free State. For arguments sake let us make it Ducks and not chickens.

 

Fandy you did not answer the one about the truck with mesh sides to let the energy created by the downward thrust "escape"???????

[TNT1]

 

I grew up on a farm and never saw one chicken fly. They can run in circles with their heads cut of though.

 

you never threw them high enough

 

 

WTF? Do you cut their heads off and then throw them up in the air? You okes from the states are weird.

 

[davetapson]

Once had a front wheel come off a volla I was driving.  Wheel definitely took off faster than the car (I was doing 130 - flat out down a hill to see how fast it would go).

 

So, to all the Einstiens, you got to take that the wheel was driven out of the equation - volla front wheels just freewheel...

 

Johann - what do you do that so many people throw wheels at you!?  And for that matter were you on the R55 coming out of Pta in 1997 anywhere near a 3 wheel beetle chasing another wheel..!?

 

[Mudsimus]

Once had a front wheel come off a volla I was driving.  Wheel definitely took off faster than the car (I was doing 130 - flat out down a hill to see how fast it would go).

 

Thats a bloodly lie if I've ever heard one! No volla can do 130, not even down a mineshaft!

[Iwan Kemp]

Not sure of the exact science, but years and years of experience in the transport industry have taught me that once a truck's wheel come off it overtakes the truck. I suppose it has something to do with the wheel travelling at 80/90km/h under HEAVY load and then being released.

In 2003 one of our trucks unfortunately had a wheel come loose on the N1 between Bloem and Colesberg.

Sadly it hit an on-coming car head-on killing one of the passengers and serverly inguring the other two.

[davetapson]

 

Once had a front wheel come off a volla I was driving.  Wheel definitely took off faster than the car (I was doing 130 - flat out down a hill to see how fast it would go).

 

 

 

Thats a bloodly lie if I've ever heard one! No volla can do 130' date=' not even down a mineshaft!

[/quote']

 

S'trues bob.  Was quite impressed.  Then the wheel came off...

 

Maybe the wheel coming off dragged the volla faster...?

 

[Veloce]

 

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.

 

I agree that the only contributing factor here is the removal of resistive forces, however consider this:

If a wheel was being spun on a motor via a concentric shaft (lets assume a frictionless shaft) it would reach a particular speed according to the RPM of the motor. If we cut the motor and let the wheel spin purely on the frictionless shaft now, will it speed up??

Mass of the vehicle is the key - ask Bruce!!

Veloce2008-11-13 03:06:57

[GoLefty!!]

Friction forces do play a role since friction force is the ReactionForce N x coefficient of friction, 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.