Furcurequs (aka Dwayne) questions Jim_Mich

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Fletcher
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Post by Fletcher »

jim_mich wrote:I'm not sure why Firefox shows it as gibberish, except that you are looking at the raw info of the file. Do a SaveAs download instead, which seems to work OK. This is the first time I've uploaded a WM2D file in many years.

And yes I changed the file name after doing the screen capture. I realized after first making the files that naming them Ec1 rather than Fc1 might cause confusion with eccentrically1.

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Still no good for me - reads as text file.

So I quickly rebuilt it - only thing I had to guess I think was the mass of the pulley for which I used 10 grams.

Looks almost identical to your sim & results.

21.375 seconds to achieve 50 rpm.
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Post by eccentrically1 »

jim_mich wrote:
Furcurequs wrote:jim_mich accused ME of being a liar and so I had to show him that I was telling the truth and then he turned right around and - as the evidence would seem to indicate - LIED TO ME!
I don't think I ever accused Furcurequs of being a liar.
A did a forum search of all my postings for the following terms and came up empty:
Furcurequs lie
Furcurequs liar
Furcurequs lying
Dwayne lie
Dwayne liar
Dwayne lying

So Dwayne, if I ever accused you of lying, please post a link to such.

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it's on the 3rd page of this thread:
jim_mich wrote:
Furcurequs wrote:The reason I ask is that you would probably need to have an equivalent knowledge yourself to see the kinds of mistakes that jim_mich has been making in this forum when it comes to basic physics equations - including his so-called "radius of gyration" calculations.
Machinery's Handbook, Copyright 1914, by Industrial Press, New York
Link to a Google Books copy of Machinery's Handbook:



Radius of Gyration from Wikipedia: http://en.wikipedia.org/wiki/Radius_of_gyration

This kind of talk about "the kinds of mistakes that jim_mich has been making" are down right lies.

Edited to add, Old Arabian Proverb...

He who knows not, and knows not that he knows not, is a fool.
Shun him.

He who knows not, and knows that he knows not is a child.
Teach him.

He who knows, and knows not that he knows, is asleep.
Waken him.

He who knows, and knows that he knows is wise.
Follow him.

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look how one tiny mistake has caused so much angst. and for what? what has been accomplished? no one ever learns anything, or changes their behavior. i'd like to again emphasize the insurmountable hurdle everyone is attempting to clear here, bolstered by their faith in bessler's alleged perpetual motion wheel. metaphorically, you are trying to give life to something that can't receive it.
that is all of physics in a nutshell.


edit: i took the machinery handbook link out because it didn't wrap around.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

You calculate as if you have 2500 grams at 1 (.97 cm) meter. I believe that is incorrect; you should not place the 500 g at one meter. The mass has leverage just as much as the force has leverage. If you calculate that you have 50 g of force (.4905 N) at 1 meter then you will also have to calculate that you have 50 g of mass at one meter. Otherwise you are giving the mass a leverage advantage over its own force.

If you act as if there is a 50g force at one meter then you have to act as if there is a 50 gram mass at one meter and say that there is an equivalent of 2050 grams at one meter. This would give you F = ma; .4905 N = 2.050 kg * a = .2392 m/sec². This is the same acceleration as you get when you move the 2 kilograms to the .1 m and let it act as 20 kg.

Another way to look at it is: that there is no radius of gyration for the 500 grams. If the 500 grams was in the system alone and the pulley was mass-less and the bearing was perfect; the 500 grams would accelerate at 9.81 m/sec². No radius of gyration would need to be calculated for the 500 grams. Even when it is in a system with the 2 kg there is still no need to calculate a RoG for the 500 grams. The force and the mass are at the same radius.

That which needs a radius of gyration is the 2 kg and it is at one meter over a force at .1 meter.

By imagining that the force is moved to the 1 meter position; you reduce the force to one tenth but then you imagine that that acceleration of .2392 m/sec² occurs there at the rim. And 5.12 m/sec velocity at the rim can only be achieved after a drop of 5.479 meters at the .1 meter pulley. And it would take 21.4 seconds.

But from experiments the .2392 m/sec² acceleration occurs at the .1 meter radius (where the force is) not at the 1 meter radius (where the accelerated mass * RoG is). This means that our target velocity is .512 m/sec and that can be achieved at .5479 meters drop and it will take 2.14 seconds.

The proof is in the pudding as they say: I have set up scores of very similar experiments and they work; if you calculate that the acceleration occurs at the point of the applied force. I do not have a ceiling 5.5 meters high yet I do these experiments all the time.
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Post by jim_mich »

Pequaide, obviously you (and others) do not understand the concept of radius of gyration. When you have weights of different mass located at different radii, it becomes complex and difficult to figure out what will happen. Your writing about this shows that it is a complex problem. The more outward weight will end up moving faster due to its greater radius. You cannot simply move this 2000 gram weight to the more inward radius and expect it to act the same.

Many years ago, people who worked hands on with machinery learned how to accurately calculate the expected results. They knew that if all of the weight in a rotating system were moved to a specific radius, then the system would function exactly like when the weights were spread out. They devised a formula for calculating this fictitious radius. So if you move the 500 grams outward to this radius and you move the 2000 grams inward to the same radius, then the whole assembly will act exactly the same as before. And with all of the weight located as a single radius, the amount of force and the time involve can be calculated using simple formulas.

The formula for calculating this radius of gyration is rather simple....
Two weights at the same radius can be considered as one weight.
Thus the two 1 Kg weights can be figured as a single 2 Kg weight.
So now you have a 2 Kg Weight at 1 Meter and a 1/2 Kg weight at 0.10 meter.

Assign R and W to be the Radius and Weight of one weight.
Assign r and w to be the radius and weight of the second weight.

The formula for Radius of Gyration is:
RoG = (R²×W+r²×w)÷(R×W+r×w)

Filling in the values:
RoG = (100²×2000+10²×500)÷(100×2000+10×500)

Radius of Gyration result:
RoG = 97.804878 cm

Simply stated, the assembly of the two weights at different radii (the machine) will function exactly as if all 2.5 Kg is located at 97.804878 cm

This assumed both weights are point mass weights. In reality a large spread-out weight will act different from a small compact weight even when both weigh the same. Radius of Gyration formulas can be used to compensate for such discrepancies. These are formula that real hands on engineers know and use out in the work place. The ivory tower engineers seldom bother with such mundane details of accuracy.

Pequaide, in your experiments, I've often seen you using wheels and then attempt to use their mass as if it were all located at the outer rim. This screws up the results. There are available specific formulas for specific shapes of rotating objects. A solid wheel acts as if all of its weight mass is located at 0.7071 times its radius. Thus if you have a solid 2 meter diameter cast iron wheel, you can assume that all of its weight mass is located at a radius of 0.7071 meters. If you don't understand this effect and assume all of the weight is at the 1 meter rim, or assume all the weight is half way out at 0.5 meter, then all the rest of your calculation will be wrong. This was the point I was attempting to make in that post from a year and a half ago.


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Post by jim_mich »

Now this machine acts like 2500 grams is located at 97.804878 cm, while the 500 gram weight force causing rotation is located at 10 cm. Thus you have a lever arrangement. Applying 500 grams at 10 cm leverages to 51.1222 grams of force acting at 97.804878 cm. (Note that this is the step where I originally made an error. The error was not in the Radius of Gyration calculation.)

So simply assume that you have 2500 grams of mass located at a radius of 97.804878 cm being moved by 51.1222 grams of force. From that info, the time needed to accelerate up to 50 RPM can be calculated.


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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

First; thanks for the .7071 radius for the solid wheel. I think the lecturer from 'A level physics' said .5 for moment of inertia but I knew that made no sense. The inertia of a solid disk is way beyond .5 r. I think I calculated it with Excel once.

You say I can't just move the 2000 g mass around; but you are moving the 500 g mass around, why can't I. I think it is just as legitimate to move the 2000 g to .1 and multiply by ten as it is to move the 4.905 newton force to 1.0 m and divide by ten.

I don't think I have much problem with RoG; but I am having a problem with thinking that a 2500 gram rim at .978 m is as easily moved as a 2000 gram rim at 1 m combined with a 500 gram rim at .1 m. Those 2.2 cm just can't change it that much. But maybe I am wrong.

Adding the 500 g to get 2500 g gives you the 25.5 seconds: instead of adding 50 g for 2050 g at one meter that will yield 21.4 seconds.

I do know that 21.4 second is way to long and 5.4 meters is way to high. I have wheels that are very much in the mass range relationships of this thought experiment. I have two kilogram wheels with which I drop increments of just 10 grams at different radii. And I have a 70 kilogram rim mass flywheel where I use increments of 100 grams dropped at different radii. The small wheel I operate at table top height; and the big wheel is at eye level. I don't recall dropping over a meter. I recall .8 m being used a lot. I don't recall times much over 6 seconds, 2 seconds is very common.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by Fletcher »

pequaide .. this appears to be a reoccurring theme for you.

jim_mich & I used rods to connect to the 1 meter radius weights at 1 kg each - rods in the sim program are treated as massless so that the mass & inertia of a crossbar [no matter how small] does not effect the result however insignificant.

Anyone, including you, with the available resources could build a test bed setup like this - the center pulley could be turned by a light chord & a hanging mass just like an Atwoods - of course a cross bar should have as little mass as possible as should the pulley.

Providing the details of the physical build are given then a sim replication can be duplicated [though it wouldn't include the mass of the unwinding chord] - in this case it isn't necessary to sim an full Atwoods but just use a Force [Weight Force] of 500 gms = 4.905N acting at 10 cm radius & rotating with the pulley.

I'm pretty sure that this is similar to what Tarseir did in a real build to test weights inertia at different radii in terms of time to unwind the hanging weight etc.

He was testing the hypothesis whether inertia was closer to mr or mr^2 & this was an easy way to see & understand the result visually.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

I do experiments not sims.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

Tarseirs experiment was a lie; you can not get those results.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

Tarsier posted the data he thought would be correct to prove mr². But in fact he did not even get that correct. The data was made up; he presented the data he thought would be correct; but he did the math wrong.

The false data undoubtedly did damage and I see Fletcher as a co conspirator because I think he would have caught Tarsier's math error but instead he keeps repeating his falsified data as fact.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by daxwc »

I had seen pictures of Tarsier’s tests at the time he did them. He defiantly wasn’t trying to hide facts; that said I do not know if the experiments were done correctly, but I imagine they are close.
What goes around, comes around.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by pequaide »

When an experimenter finds what he thinks he needed, that is a dead giveaway that, the data was invented. Especially when you are made aware of the math error and you keep reporting the data.
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re: Furcurequs (aka Dwayne) questions Jim_Mich

Post by daxwc »

But he was trying to find the opposite.... anyway I will let him speak for himself.
What goes around, comes around.
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Post by ruggerodk »

jim_mich wrote:The formula for calculating this radius of gyration is rather simple....

The formula for Radius of Gyration is:
RoG = (R²×W+r²×w)÷(R×W+r×w)

Filling in the values:
RoG = (100²×2000+10²×500)÷(100×2000+10×500)

Radius of Gyration result:
RoG = 97.804878 cm
Are you sure..?
Calculating the values you filled in gives me either:

= ((10,000*2,000)+(100*500))÷(200,000+(10*500))
= (20,000,000+50,000)÷(200,000+5,000)
= 20,050,000÷205,000
= 19,845,000

or
= (20,000,000+100*500)÷(200,000+10*500)
= (20,000,100*500)÷(20,010*500)
= 10,000,050,000÷10,005,000
= 9,990,045

regards
ruggero ;-)
Contradictions do not exist.
Whenever you think you are facing a contradiction, check your premises.
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Another question of falling

Post by ruggerodk »

All this makes my head spinning...and now I wonder if I ever be able to calculate the falling time of these simple figures?

Maybe one of you could provide the correct answer? Please...

Well, anyway the free fall should be obvious though ;-)

regards
ruggero ;-)
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Contradictions do not exist.
Whenever you think you are facing a contradiction, check your premises.
You will find that one of them is wrong. - Ayn Rand -
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