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Can I set my own bindings?



 
 
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  #51  
Old February 17th 07, 12:55 AM posted to rec.skiing.alpine
VtSkier
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Posts: 1,233
Default Can I set my own bindings?

Walt wrote:
VtSkier wrote:
Walt wrote:


... torque is force applied at some distance,


Yes, but isn't that what WORK/ENERGY is?



Work is force acting though a distance: W = F(dot)d. With torque, the
force is perpendicular to the distance vector , so when you compute the
dot product you get zero.

Torque, like distance and force, is a vector quantity while energy
(work) is a scalar. To compute torque, you take the vector cross
product of force and position vector: T = F x d. This gives a vector,
unlike the dot product above which gives a scalar.

To say a vector (torque) is equal to a scalar (energy) is like saying
Wednesday is equal to cheese. It makes no sense.


//Walt


Whether or not torque and work are directly
equivalent, they are use interchangeably in
many ways.

By adding the element of time to work we get the
concept of "horsepower". When James Watt observed
that a horse, on average, could lift (I'm sure he
used "lift" in some way so that he didn't have
(much) friction to deal with) 550 pounds one foot
in one second, he decided that moving 550 pound,
one foot in one second would be a measure of power
called "One Horsepower".

This is all well and good. The "work" is linear
and the time it takes to do the work is one second.

When talking about engines which produce useful
work in a rotational way, we speak of torque and
horsepower. Horsepower being basically the speed
at which the torque is produced. We don't need to
get into the various uses of that power which
requires maximum horsepower to be produced at
low speed or high speed, that's the subject of
another discussion and is not germain to this one.

The "horsepower" unit was devised for the speed of
linear work. It is very useful in describing the
speed of rotational work.

Torque is not a vector, it is work applied in a
vector (rotational) direction. Some of your
earlier argument suggested that torque can be
measured if the the object that the torque is
being applied to does not move. I suggested that
while the *potential* torque can be measured there
is no work/torque performed until the object moves.

Yes, you can apply a lot of force and still not
have the nut move. You can also apply a lot of
force trying to move a rock and no work is
accomplished until the rock does move, in a
linear way. This is directly analogous to to
the nut not moving in your example. The reason
that torque and work/energy use the same units
is that they really are the same thing.

If the thing doesn't move, there is only force,
no work or torque. If the thing moves over a
distance, linear or rotational, there is work/
torque. If you measure the rate at which this
work or torque is taking place, the unit you
use to describe either linear or rotational
power is *horsepower*.

The argument I'm making here is that the only
difference between force/work and torque is
the direction the force is applied. Linear for
force/work, rotational/vector for torque.
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  #52  
Old February 19th 07, 02:40 AM posted to rec.skiing.alpine
Walt
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Posts: 626
Default Can I set my own bindings?

VtSkier wrote:
Torque is not a vector,


Um....no. It is most certainly a vector quantity.

Please see http://en.wikipedia.org/wiki/Torque , or if you're a stickler
for reliable sources, any elementary physics text like Hailliday and
Resnick, or Sears and Zemansky.

You're mixing concepts. Yes, torque is *related* to power, which is
*related* to energy, which is *related* to momentum (both linear and
angular) but these are all distinct concepts.

Once you've sorted it out we can talk.


//Walt
  #53  
Old February 19th 07, 11:49 AM posted to rec.skiing.alpine
VtSkier
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Posts: 1,233
Default Can I set my own bindings?

Walt wrote:
VtSkier wrote:
Torque is not a vector,


Um....no. It is most certainly a vector quantity.


not to be too much of a stickler here,
Torque is not a vector quantity, it HAS a vector
quantity. As opposed to a straight line quantity
as in work/power which is what I've been saying.

Please see http://en.wikipedia.org/wiki/Torque , or if you're a stickler
for reliable sources, any elementary physics text like Hailliday and
Resnick, or Sears and Zemansky.

You're mixing concepts. Yes, torque is *related* to power, which is
*related* to energy, which is *related* to momentum (both linear and
angular) but these are all distinct concepts.

Once you've sorted it out we can talk.


//Walt

  #54  
Old February 19th 07, 12:05 PM posted to rec.skiing.alpine
VtSkier
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Posts: 1,233
Default Can I set my own bindings?

Walt wrote:
VtSkier wrote:
Torque is not a vector,


Um....no. It is most certainly a vector quantity.

Please see http://en.wikipedia.org/wiki/Torque , or if you're a stickler
for reliable sources, any elementary physics text like Hailliday and
Resnick, or Sears and Zemansky.

You're mixing concepts. Yes, torque is *related* to power, which is
*related* to energy, which is *related* to momentum (both linear and
angular) but these are all distinct concepts.

Once you've sorted it out we can talk.


//Walt


Having read the wiki, I don't see much difference
in what I've been saying.

At one point you claimed that you were exerting
torque on a nut if you were *trying* to turn it.
In "common usage", you are correct, but not
according to the definitions in the wiki, which
do agree with my sophomore in high school text
books.

Also, if there are definitions which pertain to
particle or nuclear physics, I'm not aware of them
and don't pretend to be applying them.
Where is Physics Man when you need him?

In all of the wiki, I can find no instance where
if there is no motion there is torque.

Stated the other way, if there is no motion, there
is no torque.

Yes, there are special cases and special definitions
to suit one's specialty be it lever design or
auto mechanics. But from what I've seen, torque
is work in a rotational or angular mode.

Certainly this is what torque is when applied to
the rating of an automobile engine.
  #55  
Old February 19th 07, 03:08 PM posted to rec.skiing.alpine
Walt
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Posts: 1,188
Default Can I set my own bindings?

VtSkier wrote:


Having read the wiki, I don't see much difference
in what I've been saying.


Here are the differences:

You are confusing two distinct concepts, torque and work. They are
different but related ideas. They are *not* the same.

You are saying that torque is not a vector. It is.

You are saying that there must be motion to have torque. Not true. See
below.


In all of the wiki, I can find no instance where
if there is no motion there is torque.



Look again. Here's the definition of torque:

Mathematically, the torque on a particle (which has the
position r in some reference frame) can be defined as
the cross product:

Tau = r X F

where

r is the particle's position vector
F is the force acting on the particle,

So, to have torque, all you need is a force. There does not have to be
motion. It's the cross product of two vectors, so it is by definition a
vector.


Stated the other way, if there is no motion, there
is no torque.


No.

Think of it this way: I'm testing a binding. I place a boot in the
binding and apply a torque of, say, 50 Newton Meters. The binding
doesn't release. I've just described a situation where there is torque
but no motion. Do you say there is no torque here? If so, how does one
ever test a binding?

torque is work in a rotational or angular mode.


Torque produces work when there is motion, according to W = T dot theta
(where theta is the angle the torque moves through and dot is the vector
dot product). The relationship between torque and work is very simple,
but the two are different concepts.

Similarly, force produces work when there is motion, according to W = F
dot d (where d is the distance the force acts through and again dot is
the vector dot product). Here force and work are related in a very
simple manner, but that doesn't mean that force *is* work. They are
different but related concepts.

In particular, force can exist without motion. When that happens, there
is no work. Likewise torque can exist without motion. Again there is
no work if there is no motion.


//Walt
  #56  
Old February 19th 07, 04:45 PM posted to rec.skiing.alpine
down_hill
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Posts: 812
Default Can I set my own bindings?

Walt wrote:


Think of it this way: I'm testing a binding. I place a boot in the
binding and apply a torque of, say, 50 Newton Meters. The binding
doesn't release. I've just described a situation where there is torque
but no motion. Do you say there is no torque here? If so, how does one
ever test a binding?



What are the springs doing? Are they not being compressed motion? I
was trying to think of a torque but no motion example but it seems to
depend where you measure something. If you take a dragster with
automatic transmissions on the start line, engine loaded brakes locked
would be my example. If you look at whole picture it fits statement if
you look at componets it fails.
  #57  
Old February 19th 07, 06:33 PM posted to rec.skiing.alpine
VtSkier
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Posts: 1,233
Default Can I set my own bindings?

Walt wrote:
VtSkier wrote:


Having read the wiki, I don't see much difference
in what I've been saying.


Here are the differences:

You are confusing two distinct concepts, torque and work. They are
different but related ideas. They are *not* the same.

You are saying that torque is not a vector. It is.

You are saying that there must be motion to have torque. Not true. See
below.


In all of the wiki, I can find no instance where
if there is no motion there is torque.



Look again. Here's the definition of torque:

Mathematically, the torque on a particle (which has the
position r in some reference frame) can be defined as
the cross product:

Tau = r X F

where

r is the particle's position vector
F is the force acting on the particle,

So, to have torque, all you need is a force. There does not have to be
motion. It's the cross product of two vectors, so it is by definition a
vector.


From wiki
http://en.wikipedia.org/wiki/Vector_(spatial)
"In physics and in vector calculus, a spatial vector,
or simply vector, is a concept characterized by a
magnitude and a direction."

Further down the page, magnitude is intentionally
used interchangeably with "length" in effect saying
it's the same thing.

Then "magnitude" = "distance", to which you add
"direction" to define "torque" as opposed to "work".
The only difference.

Stated the other way, if there is no motion, there
is no torque.


No.

Think of it this way: I'm testing a binding. I place a boot in the
binding and apply a torque of, say, 50 Newton Meters. The binding
doesn't release. I've just described a situation where there is torque
but no motion. Do you say there is no torque here? If so, how does one
ever test a binding?


You are NOT applying TORQUE to the torque wrench, you are only
applying FORCE of 50 Newtons. There is no TORQUE until there
is movement (of the binding releasing). You are measuring
POTENTIAL TORQUE, which the wrench reads in Newton-Meters
because when the TORQUE happens (by movement) that's what
it will be.

Another example. If I have an object that WEIGHS one pound,
I have to apply a FORCE of at least one pound in the direction
opposite to the FORCE provided by gravity in order to lift it.
There is NO WORK until I have moved the object a distance.
There certainly is FORCE being applied, but until the object
is moved, there has been only POTENTIAL WORK.

By all the definitions you have supplied, both TORQUE and WORK
require movement of a force over a distance.

torque is work in a rotational or angular mode.


Torque produces work when there is motion, according to W = T dot theta
(where theta is the angle the torque moves through and dot is the vector
dot product). The relationship between torque and work is very simple,
but the two are different concepts.


Yes, but look at the definition of VECTOR

Similarly, force produces work when there is motion, according to W = F
dot d (where d is the distance the force acts through and again dot is
the vector dot product). Here force and work are related in a very
simple manner, but that doesn't mean that force *is* work. They are
different but related concepts.


That's correct, but force does not have a movement (distance,
vector, etc.) component.

In particular, force can exist without motion. When that happens, there
is no work. Likewise torque can exist without motion. Again there is
no work if there is no motion.


I've been saying this all along except that TORQUE cannot
exist without motion.

TORQUE is a measure of WORK in a specified direction.

I think the confusion comes in everyday usage as opposed
to scientific usage. Our measuring tools do this to us
also. A Torque Wrench, as you appropriately point out is
notated in measures of torque, newton-meters or pound-
feet. Mine is an old one and is in foot-pounds (exactly
analogous to pound-feet) and I've used the ski shop
wrenches calibrated in newton-meters.

Like the lifting an object example, you apply force
to the wrench and no torque exists until the binding
releases. The potential torque is what you are measuring,
which IS Force, but once again, no torque until the
thing moves (in a rotational way, a vector).
  #58  
Old February 19th 07, 06:54 PM posted to rec.skiing.alpine
VtSkier
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Posts: 1,233
Default Can I set my own bindings?

down_hill wrote:
Walt wrote:


Think of it this way: I'm testing a binding. I place a boot in the
binding and apply a torque of, say, 50 Newton Meters. The binding
doesn't release. I've just described a situation where there is
torque but no motion. Do you say there is no torque here? If so, how
does one ever test a binding?



What are the springs doing? Are they not being compressed motion? I
was trying to think of a torque but no motion example but it seems to
depend where you measure something. If you take a dragster with
automatic transmissions on the start line, engine loaded brakes locked
would be my example. If you look at whole picture it fits statement if
you look at componets it fails.


In the binding:

The springs are providing a force to oppose the preset
release setting until the force needed to release the
binding has been reached. At which point there will
be torque because motion has been added to the force.

In some (most, I hope) bindings, the springs will compress
to provide "flexibility" and a return to center when
release potential is reached but only momentarily
and I guess that torque is produced in this
scenario because there certainly is motion, but
to that point at which the motion begins, you
have only applied force or potential torque to
the binding, and the torque wrench will measure
the point at which that motion begins.

In the dragster:

Because the parts in the engine are moving, there is
torque. This is a measure of work. Because you are
not allowing the dragster to move, this torque is
being dissipated as heat in the transmission until
you dump the brakes when it will be sent immediately
to the drive wheels.

In the dragster as whole, the engine is producing
torque because the engine parts are moving. This
torque is sent as force to the transmission and
drive wheels which converts this force to work
(moving down the drag strip).

In terms of the dragster, the work is "potential"
until you dump the brakes. Potential work is
only force.

The brakes are not loaded, the transmission is. The brakes are
simply allowing the transmission to be loaded.

An automatic transmission can be visualized as two fans,
one driven by an engine and one to drive a set of
rear wheels, opposing each other in a fluid (transmission
fluid).

Now simplify this.
Take a motorized fan and opposite to this place a pinwheel.
If you start up the fan, the pinwheel will accelerate to
the speed of the fan just very slightly slower than the
driven fan.

Now hold the pinwheel in place with you hand (brake) until
the driven fan is up to speed. The pinwheel will accelerate
to the speed of the driven fan in the blink of an eye.

This is what the dragster is doing for maximum acceleration,
the skill comes from the driver knowing when the drive
wheels will break loose and acceleration will be compromised.

A car is too complex a machine to use as an example of
just one thing or concept because a whole lot of things
are happening at the same time.
  #59  
Old February 19th 07, 07:14 PM posted to rec.skiing.alpine
Walt
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Posts: 1,188
Default Can I set my own bindings?

down_hill wrote:
Walt wrote:

Think of it this way: I'm testing a binding. I place a boot in the
binding and apply a torque of, say, 50 Newton Meters. The binding
doesn't release. I've just described a situation where there is
torque but no motion. Do you say there is no torque here? If so, how
does one ever test a binding?


What are the springs doing? Are they not being compressed motion?


As you increase the torque from zero to 50 the springs compress, and
there is a small amount of motion. Once you reach 50 and stop
increasing the torque the system reaches a steady state where there is
no motion. At that point there is torque but no motion.

I was trying to think of a torque but no motion example...


Here's a more visceral example: pick up a brick and hold it straight
out in front of you with your arm horizontal. Hold it still. Then
please try to explain, without allowing the brick to move, how there is
no torque since there is no motion.

//Walt
  #60  
Old February 19th 07, 07:51 PM posted to rec.skiing.alpine
Richard Henry
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Posts: 3,756
Default Can I set my own bindings?

Is this replacing the annual percent-slope-versus-angle thread?

 




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