Maybe they did not misinterpret Galileo's thought experiments - he did not actually perform them - and are living in the 21st Century.
http://books.google.nl/books?id=dF4...wBTgK#v=onepage&q=gait on a treadmill&f=false
-
Security incident: ISF was recently accessed by intruders. Please change your password, and change it anywhere else you used it. Read more
Merged DDWFTTW in a “Real” Wind
- Thread starter ynot
- Start date
- Status
Maybe they did not misinterpret Galileo's thought experiments - he did not actually perform them - and are living in the 21st Century.
http://books.google.nl/books?id=dF4...wBTgK#v=onepage&q=gait on a treadmill&f=false
Flawed assertion.
PPG
Apparently you missed the part that IFORs are never attached to accelerating or rotating objects. In fact, IFORs are never attached to objects at all. At best, you can index or use an object as a reference. Once the object accelerates or rotates, the IFOR is no longer indexed to that object but it still exists (as much as any purely mathematical concept ever exists) and can be used to measure the objects acceleration or rotation in the frame. A FOR can be indexed to any object but again if false forces appear (due to acceleration or rotation), the implication is that FOR is not an IFOR any longer.
In your example, with the "marked X", you are correct that if the FOR is permanently indexed to the X, the FOR is not an IFOR-good work! But if the IFOR is indexed to the X only initially when the X is on top of the belt (assuming no rotation or acceleration of the TM frame and constant belt speed) then assuming that the "zero" point for the major axis of the IFOR smoothly translates away from the treadmill ("down treadmill") at the speed of the original "X" then it remains an IFOR for all time. The posters assumed that anyone alleging an understanding of basic physics would understand the obvious nature of this definition of the IFOR and would not have to explain it in such absurdly definite terms as I just have. Please read this carefully and if it is not clear, you will make the same errors again.
If your understanding is as stated by your assertion, that anybody claiming TM invariance, ever assumed the IFOR would whip around the rollers with the TM belt, then, You can drop this assumption as it is naive to the point of absurdity for anyone with the least competence in basic physics.
If it helps your understanding, for the purpose of this discussion, assume a level treadmill 10" off the earth. The IFOR that we are discussing is an IFOR with the origin for the x axis 10" above the earth and smoothly translating with respect to the earth (no acceleration or rotation) in the direction of the velocity of the top of the treadmill. This should nail it down as this is a valid IFOR and Galilean relativity is valid in this frame as it meets all the requirements for an IFOR. You will notice that an object sitting on the TM belt and not moving wrt to this belt is also not moving in the defined IFOR as long as it is on the TM surface (this won't be long because it will fall off the back soon.)
I would like to think this clears it up for you but I'm no longer hopeful.
WindGrins
PPG
Apparently you missed the part that IFORs are never attached to accelerating or rotating objects. In fact, IFORs are never attached to objects at all. At best, you can index or use an object as a reference. Once the object accelerates or rotates, the IFOR is no longer indexed to that object but it still exists (as much as any purely mathematical concept ever exists) and can be used to measure the objects acceleration or rotation in the frame. A FOR can be indexed to any object but again if false forces appear (due to acceleration or rotation), the implication is that FOR is not an IFOR any longer.
In your example, with the "marked X", you are correct that if the FOR is permanently indexed to the X, the FOR is not an IFOR-good work! But if the IFOR is indexed to the X only initially when the X is on top of the belt (assuming no rotation or acceleration of the TM frame and constant belt speed) then assuming that the "zero" point for the major axis of the IFOR smoothly translates away from the treadmill ("down treadmill") at the speed of the original "X" then it remains an IFOR for all time. The posters assumed that anyone alleging an understanding of basic physics would understand the obvious nature of this definition of the IFOR and would not have to explain it in such absurdly definite terms as I just have. Please read this carefully and if it is not clear, you will make the same errors again.
If your understanding is as stated by your assertion, that anybody claiming TM invariance, ever assumed the IFOR would whip around the rollers with the TM belt, then, You can drop this assumption as it is naive to the point of absurdity for anyone with the least competence in basic physics.
If it helps your understanding, for the purpose of this discussion, assume a level treadmill 10" off the earth. The IFOR that we are discussing is an IFOR with the origin for the x axis 10" above the earth and smoothly translating with respect to the earth (no acceleration or rotation) in the direction of the velocity of the top of the treadmill. This should nail it down as this is a valid IFOR and Galilean relativity is valid in this frame as it meets all the requirements for an IFOR. You will notice that an object sitting on the TM belt and not moving wrt to this belt is also not moving in the defined IFOR as long as it is on the TM surface (this won't be long because it will fall off the back soon.)
I would like to think this clears it up for you but I'm no longer hopeful.
WindGrins
Last edited:
Humber, You will be happy to note that I had no issue with PPG posting his refererence to the "earth as a valid reference frame" quote. As long as we keep in mind the idea that the IFOR is not the earth but only indexed to it, I'm fine with this.
As long as the reference is properly cited and a link is provided where everyone can read what is actually written in context, we should all be appreciative.
I certainly appreciate the reference!
WindGrins
I have known for a long time that the real problem with you understanding the TM equivalence is much simpler than most people realize. You don't know what is meant by equivalence. No one rational has said that the TM is the Earth. They say that for the purpose of testing a cart in the wind that it is equivalent.
I understand the fact that the same visual cue differences which cause your inability to understand the TM equivalence exist for runners as well. There are many references on how to ignore them and train correctly and run the same as on a road:
http://www.runningplanet.com/training/treadmill-versus-outside-running.html
It is like riding the bike at a carnival which you steer left to go right. The brain can be fooled quite easily into doing a lot of strange things. The universe not so much.
I know that you think you cannot visualize the belt as the road. I know that you cannot stand next to a TM and visualize physics from the FOR of the belt, but I also know that it is really because you are afraid to try. At some level you know you are wrong. How big would the TM have to be before you could not tell you were living on it?
Last edited:
It can't possibly be "indexed to the the Earth". If the Earth is an IFOR, then obviously the moving belt can't be, or you would have something to explain when it was switched off.
If you understand the reference you will agree that the belt can't be an IFOR, or it could not drive the wheels. There is also that other reference, showing that walking on belt is not the same as walking on the ground.
Perhaps you have inherited some misbegotten interpretation of Galileo, by dint of "getting it"
I have re-read that article, and it is quite lucid. It seems that you are hoping to prey on the word "attached", by substituting one of your own making and nescient interpretation. References are of no use to you at all.
Last edited:
The gait is different because people adapt, not because the conditions are the same. And you should have read the section "Control of TSP's" before shooting yourself in the foot by posting another reference outlining even more differences
This is a truly an unvarnished example of the Carteers' blunt refusal to accept facts that contradict their beliefs.
How big would a TM have to be before you could not tell you were living on it?
Last edited:
Yes, it can. This is why physics in a steadily moving train or boat over the earth's surface is the same as not moving. When the TM is switched off, it accelerates its belt wrt to the defined frame. This one is easy!
The TM belt is not an IFOR and neither is the earth. IFORs can be defined with respect to these objects as long as no accelerations or rotations occur of the objects. When this occurs, the IFOR becomes no longer a valid place for an index. This has nothing to do with the TM driving the wheels. The TM drives the wheels because the prop is producing a thrust which opposes motion along the TM thus driving the wheels.
Clearly this posts illustrates we have reached the root cause of your misunderstanding yet I have no hope whatsoever that it will help your understanding of the concept.
Subduction Zone
Muse
- Joined
- Dec 23, 2008
- Messages
- 999
Rats, I missed ppgharoldchristophyevgheni again. Did anyone else notice that the article he cited has the word attached in quotes. For those unfamiliar with the use of that device it means that it is not really physically attached to the Earth. But later on when convenient for him he dropped the quotes. In other words ppg pulled a humber he linked and quoted a source that disagrees with him. ppg does not even understand why the frame of reference "attached" to the Earth is not inertial.
Obviously, exactly earth sized for the some!!!
WindGrins
I think you will find that running while moving with the belt, is not the same as "running", as the belt moves underneath. You are at least guilty of equating two distinct types of motion.
Correct. The point was that measurements must be made with reference to an IFOR, and so not a rotating object.
And you missed the part where the author acknowledges that the Earth is indeed rotating, but that the effects are so small as to be negligible, so approaching the ideal of the non-rotating object.
The belt is not like that at all, and with large effects. The closest you are going to find to an IFOR, is the Earth, and certainly not a treadmill.
Verbiage.
How about the actual choice number 3:
The frame has no boundaries, the X reappears periodically in the frame moving at the same speed when it is on top of the belt. If you want to, you can also say it never leaves the frame but when it is going around the end rollers it is accelerated in the frame and when under the belt is moving twice as fast as the belt speed in the frame. This is the correct statement about the X painted on the belt in the agreed upon IFOR. The reason we are only worrying about the top of the belt is that is where the little carts operate.
WindGrins
Obviously, exactly earth sized for some!!!
WindGrins
Some have a definite self-referencing frame of reference.
Duffy asked how big the belt would need to be, but how about how small?
I think a small roller would power the cart. Perhaps it could balance on it at "WS", rather like a parrot on a perch.
Motion may be accommodated by a series of rollers, and the cart could then be equated with one traveling faster than the wind
And what would that be the GT of? A road made of rollers, what else?
Just like the belt would be a bigger belt.
Humber this post is completely incoherent. I will help you but you will need to re-think your questions first. If you are suggesting a frictionless road don't forget a prop cart would not work on it. We need to leverage the wheels against a surface which is moving at a different speed than the air. You can't go faster than than the wind in a balloon either.
An ice boat is not a land yacht. And none of those references say they can do that while staying within 20 degrees of DDW.
No, they were yours, a month or so ago.
Wrong
You do realize that all that needs done is to multiply all the terms in my equation by V_Cart, and you will have your ridiculously redundant equation, don't you?
profpangloss
Critical Thinker
- Joined
- May 1, 2011
- Messages
- 391
Since the "X" is accelerated in the frame you are using, and the "X" is painted on the belt, the BELT is accelerated in the frame. There is no way out of that for you.
Now, since the belt is a continuous loop, and it undergoes acceleration in some places, how can it not undergo acceleration in all places? Is it because the acceleration takes place only at the ends, where it goes around the cylinders?
The motor is only at one end of the belt, yet when it accelerates the belt, the entire belt must accelerate, or do you not agree with this?
Since the ends of the belt going around the cylinders undergo acceleration, that acceleration must be transmitted along the entire belt, in the same way the motor transmits motion along the entire belt.
There is no way you can talk around this with your babble! You cannot isolate the top of the belt from the forces acting on the belt elsewhere. You cannot "attach" an IFOR to a belt that is rotating in that frame, as the "X" would definitely be doing. You cannot base a FOR on a projection. Give it up; the treadmill is dead.
If I understand the referenced articles correctly, there are two fundamental differences for walkers:
1. Normal treadmill motors are insufficient to maintain a constant unaccelerated speed with respect to the walkers weight which can bias the measurments.
2. Physiological Reaction to the TM causes the walker to adjust their gate differently than they do while walking on the ground. This may be a function of the conflicting visual information of no motion or it might be a function of the walker is not constrained on the ground to hold a tight fixed linear speed (as they are to remain on the TM). It isn't clear why adult walkers do this (it was stated that children don't seem to.) but it is not because of the pure physics of the situation except as referenced in 1. above.
Absolutely agreed to the first statement but for the 2nd: I've stated this exact same idea in multiple previous posts in even more explicit detail.
You seem to ignore that IFORs again are mathematics and physics concepts and not objects. You also missed the idea that an IFOR can be perfectly defined wrt the earth and yet smoothly translating. In fact, in the paragraph below you show incredulity that a smoothly translating (wrt earth) IFOR can even exist!
Suffice it to say. There are infinite perfectly valid IFORs' that can be defined that are smoothly moving wrt earth and any indexed to the motion of the top of the TM is perfectly valid.
PPG can't seem to separate the concept of the IFOR is not "attached" to the TM belt but is referenced to it and so continues to state confused concepts about this.
WindGrins
Put the entire cart on the rollers with a smooth surface over them and this is fine as long as it fits and doesn't run off. This just happens to be the definition of a TM.
Windgrins
If I draw an "X" on the road, it is accelerated because I pass it in my car?
Your whole argument is gibberish (as I suspect you are aware).
In the frame of reference of the cart on the treadmill the "X" you drew is just a mark on the road that passes by periodically. To the cart, it looks like a series of "X" symbols were painted at equal intervals along a straight, level road.
-- Roger
Last edited:
- Status