[Bored chemist]

And he thinks I'm bad at maths and physics because I have better things to do than to answer irrelevant high-school mechanics problems for him.

I didn't say you are bad at math. Only not as good as you are at chemistry.
A good mathematician or physicist will be able to answer my questions in mere minutes, or even seconds, which can be much faster than what it takes for you to type a post in this thread.

Did you understand this "irrelevant"?

[hamdani yusuf (OP)]

Here's another thought experiment. This picture shows a table with rounded feet on a smooth floor. Its weight is distributed evenly between its leg on the left and right sides. The floor exerts normal force equal and opposite to the total weight, thus the table is stationary.


A force is applied to the top right corner of the table, directed 45 degree to the up left direction. The table is only accelerated horizontally, but isn't accelerated vertically. It doesn't rotate, hence the net torque is zero.


Just like before, a force is applied to the top right corner of the table, directed 45 degree to the up left direction. But a wedge is placed to the left side of the left leg. The left leg of the table is raised while the right leg is not. Thus it is rotated clockwise.


Just like before, a force is applied to the top right corner of the table, directed 45 degree to the up left direction. But a wedge is placed to the left side of the right leg. The right leg of the table is raised while the left leg is not. Thus it is rotated counter-clockwise.


I show this to emphasize that the same active force to the same object can produce different torque which lead to different rotation of the object.

[hamdani yusuf (OP)]

And he thinks I'm bad at maths and physics because I have better things to do than to answer irrelevant high-school mechanics problems for him.

I didn't say you are bad at math. Only not as good as you are at chemistry.
A good mathematician or physicist will be able to answer my questions in mere minutes, or even seconds, which can be much faster than what it takes for you to type a post in this thread.

Did you understand this "irrelevant"?

Yet you have the time to read my posts and write your own replies. Perhaps the questions have higher requirements to answer than what you can provide.

[Bored chemist]

You don't seem to need help with simple mechanics, so I won't usually waste my time on it.

But you do seem to need help with understanding that physics is right and you are wrong.

[hamdani yusuf (OP)]

MIT Physicist Explains Torque As Simply as Possible.

Today we take a very simple approach to explaining what is quite a complex topic, torque!

I commented on the video, which sparked a heated debate with another viewer.

To avoid confusion between unit of torque and energy, torque  can be expressed as Joule per radian. Or Newton meter per radian. Dot product between force and distance produces energy, which is a scalar. Cross product between force and distance from fulcrum produces torque, which is a vector.

This strikes me as an almost surefire way to CREATE confusion and obscure the fundamental nature of torque - which is, as explained clearly in the video,  the product of force times distance (or  as alluded to in the video, more precisely  - the perpendicular component of force times distance).  Using units of torque as Joules per radian makes no physical sense. Joules are the fundamental unit of energy in the SI system, and radians is a (dimensionless) measure of an angle.  What's the angle here that relates to the definition of and understanding of the nature of torque?
When I was a Mechanical Engineering professor, I occasionally heard students use an engineering equation solving program that frequently gave answers in units that made no physical sense.  I created a "wall of shame" at the entrance to my office where everyone entering would immediately see.  If a student lacked the understanding to use appropriate units in the answer to a problem (even if the units "worked out"ok, their solution would find itself on the wall. Most assuredly, Joules per radian would make its way onto the wall. While not quite as egregiously bad, Newton-meter per radian would find itself there as well.  Adding dimensionless numbers as units to perhaps serve as a memory aid is just plain silly.  How about Joules per radian per Re per Fr?  There are a whole host of dimensionless numbers we can choose from, most of which don't add anything meaningful.

If you are confused, that's because you have misunderstood the concept. If the torque doesn't cause change of angular position, no work has been done. You'll understand better if you learn about the torque of a motor. Perhaps experimenting with variable speed drive can help.

I am not the one who is confused here. I perfectly understand that work is forced times distance or,  for a rotational system torque times angle of rotation. My point is that there is no reason to express torque in units of energy per angle of rotation. The fundamental nature of torque is force acting at a distance. Not all torques result in work being done.   Only if the torque is accompanied by a rotation then there is work being done. There is no reason to include the concept of work associated with torque for the situations where there is no work being done.That is, such as the case where the torque is applied statically. Newtons and meters are fundamental units in the SI system. Torque is readily defined in terms of these fundamental units. There is no need to introduce additional units such as radians.
 Furthermore your suggestion that I am confused and my confusion would be cleared up by looking at variables speed devices is quite condescending. I have been engineer for more than 50 years. I worked with and designed vehicle power trains, including those that had continuously variable and infinitely variable speed transmissions. In my work I worked with advanced power trains including those for hybrid vehicles and
I have co-authored numerous SAE papers on the subject, and have taught thousands of Mechanical Engineering students.  I am confident that I am not confused about the fundamental nature of torque.

Torque is the rotational equivalent of force in linear motion. It's a measure of how effectively a force can cause an object to rotate around a specific axis. It's also known as angular force.
Converting linear force into angular force can be done by multiplying it by distance (along the circumference) per angle of rotation.

Based on your  continuing replies, I can only come to the conclusion that you are being deliberately obstinate, or have been poorly educated and don't understand the true nature of torque.  You can search the archives of respectable Engineering publications such as  SAE and ASME, and you will find little, if any at all, evidence to support your position that torque should be expressed as  Joules/radian or Newton meters/rad.

I won't waste any more of my time responding to your comments - and hope that anyone who reads this string of comments is able to understand the problem in using Joules/rad. (Or any other unit of energy/radian  eg calories or BTUs/radian)

The hardest part of learning new things is to first unlearn previous knowledge that is incomplete or inaccurate. It's often easier to teach young people who hasn't been exposed too deep to those previous knowledge.
You can check the unit consistency in motor calculation for power.
P=τ⋅ω
where:
P = Power (Watts, W, Nm/s)
τ = Torque (Newton-meters per radian, Nm/rad)
ω = Angular Speed (radians per second, rad/s)

If you omit the unit radian from torque, you get incorrect unit for power.

By the like that the video author gave to my comment, it seems like he agreed with my reason. It seems like younger scientists and engineers are more open to accept new ideas compared to older ones. Perhaps it's because they carry less baggage from existing norms that they have committed to.

[hamdani yusuf (OP)]

You don't seem to need help with simple mechanics, so I won't usually waste my time on it.

But you do seem to need help with understanding that physics is right and you are wrong.

Do you find any error in my reasonings?
Can you point it out?
What's needed to make it more correct?

[alancalverd]

Except you are using a broken torque wrench.

Or an electric or pneumatic torquer.

[alancalverd]

In principle, you only need odd constants because of things like integrals or if you use inconsistent units like Calories instead of Joules.

Pi turns up from time to time in our definitions of units, and if you set h = 1 you will have engineers and market traders screaming at you.

[Bored chemist]

Do you find any error in my reasonings?
Can you point it out?

Yes
I did.
https://www.thenakedscientists.com/forum/index.php?topic=87006.msg740900#msg740900

[paul cotter]

The inability or unwillingness to learn is a severe handicap for any human.

[Bored chemist]

The inability or unwillingness to learn is a severe handicap for any human.

Many politicians seem to find otherwise, but it certainly screws up any hope of doing science.

[hamdani yusuf (OP)]

A lie requires discrepancy between what we say and what we think. It's hard to prove. IMO, it's more likely an honest mistake.

You think parents telling kids about the tooth fairy are honestly mistaken?

No. It's a lie.

[hamdani yusuf (OP)]

Except you are using a broken torque wrench.

Or an electric or pneumatic torquer.

Do you think they already show non-zero torque before you turn them?

[hamdani yusuf (OP)]

Do you find any error in my reasonings?
Can you point it out?

Yes
I did.
https://www.thenakedscientists.com/forum/index.php?topic=87006.msg740900#msg740900

Is this the best you can do?

IMO, the cost of this

And apparently, not in the opinion of anyone else at all, ever.

So, it's not changing any time soon.
Face it.

What do you think about this?

You will not find a single reference that claims the angle is a component of torque and I think you are being deliberately argumentative for argument's sake.

I'm proposing to change the STANDARD unit for torque in order to make it consistent with other rotational quantities. You can still use non-standard units, as long as they give you some benefits, like being easier to measure or calculate. You can use your own feet, palms, or fingers to measure length, for they are most accessible for you at some point in your lifetime. But I don't think they can be good standards.

Can you point out what's wrong with my previous post?

The table below shows the comparison between angular and linear quantities.

Here are the equations conversion, where d = arclength of the circumference corresponding to rotational angle.
θ = d * (θ/d)
ω = v * (θ/d)
α = a * (θ/d)
I = m * (d/θ)^2
τ = F * (d/θ)
L = p * (d/θ)

And this?

τ = I α

as {τ} = ML²T^-2 and {I} = ML², α must be in rad/sec²

You can use standard units. But you can also use non-standard units, as long as you are consistent with their usage and the conversion factors.
Let's say the torque is 1 N.m/rotation, and the rotational inertia is 1 kg.m^2/rotation^2. The rotational acceleration is 1 rotation/second^2.
If the torque is applied for 1 second, the rotational velocity of the object will be 1 rotation per second.

In standard unit, the torque above equals 1/(2π) N.m/rad
The rotational inertia is 1/(2π)^2 kg.m^2/rad^2.
The rotational acceleration is 2π rad/second^2.
If the torque is applied for 1 second, the rotational velocity of the object will be 2π rad/second.

I hope this example is simple enough for you to follow my reasoning which concludes that torque is force times distance of rotation divided by rotational angle. This equation works generally, no matter which units of angle that you choose. A complete rotation is a commonly used alternative, especially when dealing with multiple rotation. On the other hand, when dealing with small rotational angle, we can use degree, arc minute, or arc second as the measuring unit.

[hamdani yusuf (OP)]

https://en.wikipedia.org/wiki/Torque#Units

Torque has the dimension of force times distance, symbolically T−2L2M and those fundamental dimensions are the same as that for energy or work. Official SI literature indicates newton-metre, is properly denoted N⋅m, as the unit for torque; although this is dimensionally equivalent to the joule, which is the unit of energy, the latter can never used for torque.[14][15] In the case of torque, the unit is assigned to a vector, whereas for energy, it is assigned to a scalar. This means that the dimensional equivalence of the newton-metre and the joule may be applied in the former but not in the latter case. This problem is addressed in orientational analysis, which treats the radian as a base unit rather than as a dimensionless unit.

The last sentence has offered a solution.

Somehow the solution above has been ignored, although the reason is not clear.

[Bored chemist]

I'm proposing to change the STANDARD unit for torque in order to make it consistent with other rotational quantities.

And, if you think that has any hope of being adopted, it is evidence of a fault in your reasoning.

[hamdani yusuf (OP)]

I'm proposing to change the STANDARD unit for torque in order to make it consistent with other rotational quantities.

And, if you think that has any hope of being adopted, it is evidence of a fault in your reasoning.

What's your reason to come to that conclusion?
Haven't you ever found any new standard? Or a standard being changed?

[alancalverd]

I've just used a constant-torque pneumatic spanner. Initially it accelerated the rotation of the bolt according to τ = I α, then the bolt slowed down under friction and eventually stopped rotating, having reached the bottom of the thread. But τ remained constant. What happened to Hamdani's  rad?

[hamdani yusuf (OP)]

I've just used a constant-torque pneumatic spanner. Initially it accelerated the rotation of the bolt according to τ = I α, then the bolt slowed down under friction and eventually stopped rotating, having reached the bottom of the thread. But τ remained constant. What happened to Hamdani's  rad?

Since τ = I α while α = 0, and τ ≠ 0,
Then I = ∞
You need to understand how your instruments work to know their limitations in order to correctly interpret their results.
Have you ever try to measure the temperature of boiling water using alcohol thermometer?
Have you ever try to measure the temperature of a mirror using infrared thermometer?

Do you realize that when the rotation of the bolt is slowing down, the rotational acceleration is negative?

[alancalverd]

Since τ = I α while α = 0, and τ ≠ 0,
Then I = ∞

So you really need to review your understanding of torque, because  I have described exactly what happens when you tighten a bolt.