Bicycle Wheel Physics

On Wed, 26 Nov 2003 03:49:58 +0000, Jon Bond wrote:

Actually, a lot of the staying upright phenomenon has to do with the trail
of the front wheel. Not all of it, but a lot. This is why even if you're
moving backwards really frickin' fast, you're gonna go down. Hard.

You need to learn how to ride fakie

"John Morgan" wrote in message news:DRUwb.7470$9O5.6511@fed1read06...

This is the best explaination I have heard of this concept so far! Way to
break it down into layman's terms, SS. It just boggles my mind that the top
part of a wheel moves with a different speed than the bottom part!

-John Morgan

Be careful. In the picture at the top left of the diagram, the top and
bottom of the wheel actually have the same speed, but they have
different velocities. This would be the situation that occurs if you
were to detach the wheel from the bicycle, hold it by the axle and
spin it. In this case the top and bottom of the wheel are like mirror
images. They're both doing the same thing, but in opposite directions.

Now when you put the wheel back on the bike and take into account the
fact that the whole bicycle is moving forward, then the forward
velocity of the bike will cancel the backward velocity of the bottom
of the wheel, which gives the bottom of the wheel a velocity of 0. But
the velocity of the top of the wheel gets added to the velocity of the
bike, so the top of the wheel will have a velocity of 2V.

I know you already figured all this out, but for your future
adventures in physics it's worth keeping in mind that speed and
velocity are different critters. It's also important in physics to
keep track of the system of reference, i.e. it's one thing to look at
the wheel by itself, and another think to look at the wheel when it's
attached to the bike.

Brad Carmichael

"John Morgan" wrote in message
news:KrTwb.7460$9O5.4033@fed1read06...
.... why is a point at the bottom of a bicycle wheel not moving at all?

Vector diagrams are fine and all, but let's not forget the obvious...

"A point at the bottom of a bicycle wheel is not moving at all because it is
in contact with the ground."

(Insert usual disclaimers about assuming bike is not airborne, assuming
wheel is not skidding, assuming ground is the reference point, even though
its moving very very quickly relative to some things etc etc)

grum

"John Morgan" wrote in message
news:KrTwb.7460$9O5.4033@fed1read06...
They're teaching me strange things in school. Can anyone explain why a
point at the top of a rolling bicycle wheel moves twice as fast as a point
in the center of the wheel? And if you can wrap your head around that
one... why is a point at the bottom of a bicycle wheel not moving at all?

Here's the model I found in the textbook to explain it:

Piece o' **** - it's all relative! Rate of motion in this case is relative
to the ground, the bottom of the wheel is _on_ the ground, and therefore not
moving. The top of the wheel is in motion relative to the centre of the
wheel, which is half way between top and bottom, therefore it's moving twice
as fast. Duh!

',;~}~


Shaun aRe - Have a nice day now y'all, y'hear?

On Fri, 28 Nov 2003 13:47:37 -0000, "Shaun Rimmer"
wrote:


"John Morgan" wrote in message
news:KrTwb.7460$9O5.4033@fed1read06...
They're teaching me strange things in school. Can anyone explain why a
point at the top of a rolling bicycle wheel moves twice as fast as a point
in the center of the wheel? And if you can wrap your head around that
one... why is a point at the bottom of a bicycle wheel not moving at all?

Here's the model I found in the textbook to explain it:

Piece o' **** - it's all relative! Rate of motion in this case is relative
to the ground, the bottom of the wheel is _on_ the ground, and therefore not
moving. The top of the wheel is in motion relative to the centre of the
wheel, which is half way between top and bottom, therefore it's moving twice
as fast. Duh!

',;~}~


Shaun aRe - Have a nice day now y'all, y'hear?

Yeah, what he said!

Peace,
Bill

....one speed to rule them all, one speed to find them,
one speed to bring them all and on the trails pass them
In the Land of Avalon where the geared pigs lie...

"Bill Wheeler" wrote in message
...
On Fri, 28 Nov 2003 13:47:37 -0000, "Shaun Rimmer"
wrote:


"John Morgan" wrote in message
news:KrTwb.7460$9O5.4033@fed1read06...
They're teaching me strange things in school. Can anyone explain why a
point at the top of a rolling bicycle wheel moves twice as fast as a
point
in the center of the wheel? And if you can wrap your head around that
one... why is a point at the bottom of a bicycle wheel not moving at
all?

Here's the model I found in the textbook to explain it:

Piece o' **** - it's all relative! Rate of motion in this case is
relative
to the ground, the bottom of the wheel is _on_ the ground, and therefore
not
moving. The top of the wheel is in motion relative to the centre of the
wheel, which is half way between top and bottom, therefore it's moving
twice
as fast. Duh!

',;~}~


Shaun aRe - Have a nice day now y'all, y'hear?

Yeah, what he said!

Yay! What he said about what I said!

Peace,
Bill

...one speed to rule them all, one speed to find them,
one speed to bring them all and on the trails pass them
In the Land of Avalon where the geared pigs lie...


Blah-blah-blah-blah.

Shaun aRe - Some things never change, Like Wheeler. And his gears.

On Mon, 1 Dec 2003 16:20:03 -0000, "Shaun Rimmer"
wrote:



Shaun aRe - Some things never change, Like Wheeler. And his gears.


Don't got any gears to change ;-P
....one speed to rule them all, one speed to find them,
one speed to bring them all and on the trails pass them
In the Land of Avalon where the geared pigs lie...

"Bill Wheeler" wrote in message
...
On Mon, 1 Dec 2003 16:20:03 -0000, "Shaun Rimmer"
wrote:



Shaun aRe - Some things never change, Like Wheeler. And his gears.


Don't got any gears to change ;-P

That's your problem Bill. You're just limiting yourself. Many of the
others here with SS's also have full geared boingers. C'mon now you did
real good with the disc brake thing.

Mike - free your mind and your ass will follow.

"Bill Wheeler" wrote in message
...
On Mon, 1 Dec 2003 16:20:03 -0000, "Shaun Rimmer"
wrote:



Shaun aRe - Some things never change, Like Wheeler. And his gears.


Don't got any gears to change ;-P

Yes - it's still 'gearing' dude - gears are what set the ratio.


Shaun aRe

On Wed, 03 Dec 2003 13:08:30 +0000, Shaun Rimmer wrote:

Don't got any gears to change ;-P

Yes - it's still 'gearing' dude - gears are what set the ratio.

Perhaps you missed it, but Bill's now given up on the whole new-fangled
'gear' thing and gone back to *true* riding. He's now got a hobby
horse.

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