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  1. Naked Science Forum
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  4. Can we improve the standard units of rotational quantities?

Poll

Can we improve the standard units of rotational quantities?

No. They are already perfect. Any change will only make them worse.
4 (80%)
No. They have some known problems, but there is no possible solution.
0 (0%)
Yes. They have some known problems, and there are some possible solutions.
0 (0%)
Yes. They have some known problems, and one solution can solve them all.
1 (20%)

Total Members Voted: 5

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Can we improve the standard units of rotational quantities?

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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #720 on: 24/04/2025 10:36:37 »
Quote from: hamdani yusuf on 28/03/2025 15:42:53
Quote from: hamdani yusuf on 25/03/2025 15:14:06
According to their awareness of this problem, people can be classified into some categories.
1. Those who are completely ignorant of the problem. Most kids and illiterate people fall into this category. Until high school, I was also included here.
2. Those who are aware of the problem, but haven't found the solution. I was here until a few years ago.
3.Those who are aware of the problem, as well as the solution. Currently, it's the fewest.
By spreading the information about this problem and solution through social media, I hope to change the composition in the classification above to reduce the proportion of people in the first category, and at least increase the proportion of people in the second category.
A new standard needs to exceed some sort of critical mass of public exposure before it can be accepted. By showing the inconsistencies in current standard, I hope to reduce the proportion of first group in our society.

I already quoted previously proposed solutions and why they were rejected. My own proposed solution is built upon one of previous solutions, with a slight modification to eliminate its weakness. I'm still open for a better solution, if there is one.
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #721 on: 24/04/2025 10:38:03 »
Quote from: paul cotter on 24/04/2025 10:27:33
NO.
Can you describe your reason?
What is the unit of rotational angle, angular velocity, and angular acceleration?
Do you think the equation below valid?
I = 2 Ek / ω^2
« Last Edit: 24/04/2025 10:42:41 by hamdani yusuf »
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Offline alancalverd

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Re: What's the unit of Torque?
« Reply #722 on: 24/04/2025 11:14:08 »
Quote
Why isn't it free to rotate?

Because the bolt is fully tightened, the axle is rusty, I've applied the brake to the wheel, I've forgotten to remove the cotter pin, the spring is fully wound......but my torque wrench still registers an applied torque.

Quote
showing the inconsistencies in current standard,

There are none. Force x perpendicular distance from the line of action to a specified point is called "torque".
« Last Edit: 24/04/2025 11:18:25 by alancalverd »
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Offline paul cotter

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Re: What's the unit of Torque?
« Reply #723 on: 24/04/2025 15:51:11 »


There are none. Force x perpendicular distance from the line of action to a specified point is called "torque".
Precisely correct.
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #724 on: 28/04/2025 03:15:08 »
Quote from: hamdani yusuf on 24/04/2025 10:38:03
Quote from: paul cotter on 24/04/2025 10:27:33
NO.

Can you describe your reason?
What is the unit of rotational angle, angular velocity, and angular acceleration?
Do you think the equation below valid?
I = 2 Ek / ω^2

OK. These questions seem to be too difficult to answer. So I'll just answer them myself. CMIIW.
1. No.
2. radian, radian/second, radian/second^2
3. Yes.
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #725 on: 28/04/2025 03:18:42 »
Quote from: alancalverd on 24/04/2025 11:14:08
Quote
Why isn't it free to rotate?

Because the bolt is fully tightened, the axle is rusty, I've applied the brake to the wheel, I've forgotten to remove the cotter pin, the spring is fully wound......but my torque wrench still registers an applied torque.

Quote
showing the inconsistencies in current standard,

There are none. Force x perpendicular distance from the line of action to a specified point is called "torque".
Your torque wrench registers an applied torque because it has rotated by small amount angular displacement.

How do you tell people to use perpendicular distance instead of parallel distance?
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #726 on: 28/04/2025 03:23:18 »
Quote from: hamdani yusuf on 24/04/2025 06:18:50
Quote from: alancalverd on 23/04/2025 04:54:25
Quote
If τ doesn't equal Iα, how do you relate torque to angular acceleration?

Cart before horse! If you apply a torque τ to a freely rotating body I then it will accelerate at α = τ/I. But if you apply the same torque to a body that is not free to rotate, it won't.

Therefore Iα is a potential effect of torque, not a definition of it.

I covered this point several posts ago.

Quote
You are confused because my formula is not F r/θ.
Oh yes it is:
Quote
Thus the standard unit for rotational radius should be meter per radian.
Why isn't it free to rotate?
Is F=m.a?

If τ doesn't equal Iα, how do you relate torque to angular acceleration?
What do we get when rotational inertia (aka moment of inertia) is multiplied by angular acceleration?

What is the unit for arc length of a circle?
What is the unit for circumference of a circle?
These questions are also too difficult for you to answer. So here's my answers.
1. Because there's another torque acting in the opposite direction with the same magnitude.
2. yes
3. τ does equal Iα
4. Torque
5. meter
6. meter
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #727 on: 28/04/2025 03:25:08 »
Quote from: paul cotter on 24/04/2025 15:51:11


There are none. Force x perpendicular distance from the line of action to a specified point is called "torque".
Precisely correct.
How do you specify that point?
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #728 on: 28/04/2025 09:47:46 »
Torque can be viewed as tangential force. Another type of force related to rotational motion is centripetal force.
Quote
https://en.wikipedia.org/wiki/Centripetal_force

Centripetal force (from Latin centrum, "center" and petere, "to seek"[1]) is the force that makes a body follow a curved path. The direction of the centripetal force is always orthogonal to the motion of the body and towards the fixed point of the instantaneous center of curvature of the path. Isaac Newton described it as "a force by which bodies are drawn or impelled, or in any way tend, towards a point as to a centre".[2] In Newtonian mechanics, gravity provides the centripetal force causing astronomical orbits.

One common example involving centripetal force is the case in which a body moves with uniform speed along a circular path. The centripetal force is directed at right angles to the motion and also along the radius towards the centre of the circular path.[3][4] The mathematical description was derived in 1659 by the Dutch physicist Christiaan Huygens.[5][6]

From the kinematics of curved motion it is known that an object moving at tangential speed v along a path with radius of curvature r accelerates toward the center of curvature at a rate


Here, ac is the centripetal acceleration and Δv is the difference between the velocity vectors at t+Δt and t.

By Newton's second law, the cause of acceleration is a net force acting on the object, which is proportional to its mass m and its acceleration. The force, usually referred to as a centripetal force, has a magnitude[7]

 and is, like centripetal acceleration, directed toward the center of curvature of the object's trajectory.

This force is also sometimes written in terms of the angular velocity ω of the object about the center of the circle, related to the tangential velocity by the formula
v = ωr
so that
Fc = m r ω^2


A body experiencing uniform circular motion requires a centripetal force, towards the axis as shown, to maintain its circular path.
Fc = m v^2/r = m r ω^2
→ v^2/ ω^2 = r^2
→ r = v/ω
Standard unit for linear velocity is meter/second, while standard unit for angular velocity is radian/second.
It implies that standard unit for rotational radius is meter/radian, which would produce consistent units of rotational quantities as shown in the table I posted previously.

The table essentially says that converting from a linear quantity to the corresponding rotational quantity can be done by simply dividing or multiplying it by the rotational radius or its square.
The rotational radius equals to rotational displacement divided by rotational angle.

Rotational version of work is torque times rotational angle.
τ = F(d/θ)
θ = d (θ/d)
W = F.d = τ.θ = F(d/θ) . d(θ/d) = F.d
Rotational version of power is torque times angular velocity.
τ = F(d/θ)
ω = v(θ/d)
W = F.v = τ.ω = F(d/θ) . v(θ/d) = F.v
In these quantities, conversion factor of rotational radii cancel out, leaving the units for rotational version of work and power equal their linear versions.
« Last Edit: 28/04/2025 12:49:09 by hamdani yusuf »
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Offline alancalverd

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Re: What's the unit of Torque?
« Reply #729 on: 28/04/2025 22:10:11 »
Quote
How do you specify that point?

With a vector from a mutually agreed origin. Same way as we specify any other point.
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Re: What's the unit of Torque?
« Reply #730 on: 28/04/2025 22:12:55 »
 
Quote
τ does equal Iα

Not if you understand cause and effect, and the concept of limiting conditions.
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Re: What's the unit of Torque?
« Reply #731 on: 28/04/2025 23:53:40 »
Quote
Your torque wrench registers an applied torque because it has rotated by small amount angular displacement.
but not as much as the bolt I have tightened (several turns) with it.

Quote
How do you tell people to use perpendicular distance instead of parallel distance?
By the use of the English language. Other languages are available, and most of them have different words for parallel and perpendicular.
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Offline alancalverd

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Re: What's the unit of Torque?
« Reply #732 on: 28/04/2025 23:56:57 »
Quote
Torque can be viewed as tangential force.
but not by anyone who can read the definition of torque.
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Offline alancalverd

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Re: What's the unit of Torque?
« Reply #733 on: 29/04/2025 00:00:00 »
Quote
converting from a linear quantity to the corresponding rotational quantity
The word "corresponding" is key to your persistent misconception. There is no actual, implied, or necessary "correspondence". A circle does not correspond to a straight line.
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Offline paul cotter

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Re: What's the unit of Torque?
« Reply #734 on: 29/04/2025 03:59:11 »
This is becoming quite tiresome. Two highly qualified individuals, namely AC and BC and myself have repeatedly outlined your errors but when cornered you just digress and obfuscate and I personally see this as bad manners.
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Re: What's the unit of Torque?
« Reply #735 on: 29/04/2025 09:56:29 »
Quote
rotational version of work and power equal their linear versions.

Whatever became of physics? We seem to be in the realm of very poor science fiction here. Be warned, there are already several published papers on the dilithium crystal moderator, in both English and Klingon, and  within the Empire,  bad teaching carries a mandatory death sentence.
« Last Edit: 29/04/2025 10:05:53 by alancalverd »
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #736 on: 29/04/2025 13:27:41 »
Quote from: alancalverd on 28/04/2025 22:10:11
Quote
How do you specify that point?

With a vector from a mutually agreed origin. Same way as we specify any other point.
Who did you agree with?
How did you agree about it?

Let's say the object is a long thin stick 1 meter long, 1 kg mass, floating in free space. 1 N force is applied to one of its end, perpendicular to the length. What is the torque?
« Last Edit: 29/04/2025 13:30:03 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #737 on: 29/04/2025 13:31:32 »
Quote from: alancalverd on 28/04/2025 22:12:55
Quote
τ does equal Iα

Not if you understand cause and effect, and the concept of limiting conditions.
What does Iα equal to, in your opinion?
What makes it different from torque?
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Re: What's the unit of Torque?
« Reply #738 on: 29/04/2025 13:45:49 »
Quote from: alancalverd on 28/04/2025 23:53:40
Quote
Your torque wrench registers an applied torque because it has rotated by small amount angular displacement.
but not as much as the bolt I have tightened (several turns) with it.

Quote
How do you tell people to use perpendicular distance instead of parallel distance?
By the use of the English language. Other languages are available, and most of them have different words for parallel and perpendicular.
If you just install the torque wrench sock to the bolt head, your torque reading should register 0. Only if you apply some tangential force, the torque reading should register non-zero value.
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Offline hamdani yusuf (OP)

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Re: What's the unit of Torque?
« Reply #739 on: 29/04/2025 13:55:49 »
Quote from: alancalverd on 28/04/2025 23:56:57
Quote
Torque can be viewed as tangential force.
but not by anyone who can read the definition of torque.
Which one of these definitions?
a twisting force that tends to cause rotation. (oxford dictionary)

In physics and mechanics, torque is the rotational analogue of linear force. (wikipedia)
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