[hamdani yusuf (OP)]

Consequently, the box move sideways.

Accelerates, not "moves". Newton. And it won't roll because the rotational torque (100 Nm) is less than the restoring torque (about 490 Nm)

Can it accelerate without moving?
How do you calculate the restoring torque?
Did you consider the momentum of the box?

[hamdani yusuf (OP)]

Can you do it without any change in position of the lever?

In principle, yes. In practice, any real lever will bend a bit (indeed some torque wrenches use the bending to measure the tporque), but the applied torque is independent of the elasticity of the lever: whether you use a rigid bar or a flexible one, torque is just the product of force x distance.

Here's a thought experiment in a workshop. We wanted to release a bolt from a corroded valve. It's clamped on a bench using a vise. A large wrench was used in an attempt to turn the bolt to release it. After a force was applied, the bolt didn't turn. It moved the whole bench instead.
It reminds you the definition of torque in terms of cross product between force and radius of rotation. It's not the radius of the object.

Here's the diagram for simplified version of the case.

The length of the wrench only represents an expected value for the radius of rotation. But the actual rotation in this case is around the bottom of left leg of the bench. The radius that should be used to calculate torque is the radius of actual rotation.
Let me remind you that unexpected results come from false assumptions.

Now, in other case where there is no actual rotation, even so slightly, what is the radius of rotation that you will use to calculate torque?

[hamdani yusuf (OP)]

Now that you already understand how torque works, and its relationships with other rotational quantities as well as its linear counterpart, you can help other people from being confused in the future. You can help them from repeating the common mistakes that many people have made. You can contribute to improve the consistency in human knowledge by signing my petition below.
 

https://chng.it/dXwF228mj4

I've started a petition to Standardize the Unit of Torque as Joule per Radian (J/rad) Instead of Newton-Meter (N.m).

The Issue
Petition Summary:
We call upon the International System of Units (SI) and global scientific bodies to standardize Joule per Radian (J/rad) as the official unit for torque, replacing the ambiguous Newton-meter (N.m). This change will eliminate confusion between torque and work/energy, improving clarity in physics, engineering, and education.

Why This Matters:

1. Ambiguity in SI Units \ Currently, both torque and work/energy are expressed in N.m, despite being fundamentally different quantities. Torque is a vector (rotational force), while work is a scalar (energy transfer). This leads to misinterpretations in academic and industrial contexts.


2. Clarity in Scientific Communication \ Using Joule per Radian (J/rad) aligns torque directly with its definition: energy per unit angular displacement. This mirrors the linear counterpart (work = force . displacement), making equations more intuitive.


3. International Consistency \ Many fields, such as mechanical engineering and physics, already use J/rad in practical calculations. Formal adoption would unify scientific literature and teaching materials.

 

Proposed Change:

Officially define torque in Joules per Radian (J/rad) within the SI system.

Encourage textbooks, research papers, and engineering standards to transition to the new unit.


Join Us!
Sign this petition to support a clearer, more logical unit system. Let's urge ISO, NIST, BIPM, and other standardization bodies to take action!

You can also share this information in your social media. If you still aren't sure, you can ask your teachers or professors to take a look at my explanations. Perhaps they can provide a second opinion to improve my petition further.

[Bored chemist]

Now, in other case where there is no actual rotation, even so slightly, what is the radius of rotation that you will use to calculate torque?

It depends if I'm sat on the bench or stood next to it.

[hamdani yusuf (OP)]

Now, in other case where there is no actual rotation, even so slightly, what is the radius of rotation that you will use to calculate torque?

It depends if I'm sat on the bench or stood next to it.

How do they make a difference?

[hamdani yusuf (OP)]

At this point I think I have enough material to make a video that's convincing enough to change the standard unit for torque, also for rotational inertia and rotational momentum, and make them more consistent with each other, as well as their linear counterparts.

[alancalverd]

Can it accelerate without moving?

Surely you mean can it move without accelerating?

How do you calculate the restoring torque?

mgr

Did you consider the momentum of the box?

depends on how long the accelerating force has been acting.

[alancalverd]

I think I have enough material to make a video

Please don't pollute the cybersphere with drivel. Leave that to priests, politicians and philosophers.

[hamdani yusuf (OP)]

Surely you mean can it move without accelerating?

Moving is more general than accelerating.
You can't be a human without being a primate.

[hamdani yusuf (OP)]

mgr

m = 100 kg
g = 9.8 m/s^2
r = 0.5 m
mgr = 490 kg.m^2/s^2
Did you calculate its rotational inertia?

[hamdani yusuf (OP)]

depends on how long the accelerating force has been acting.

So, your conclusion that it won't roll is premature.

[hamdani yusuf (OP)]

I think I have enough material to make a video

Please don't pollute the cybersphere with drivel. Leave that to priests, politicians and philosophers.

It is important for any standard to be consistent.
The fact that this inconsistencies have been around for so long suggests that it takes a holistic approach to convince people to fix them. A video enables its viewer to imagine the dynamic model of the rotational system, unlike a paper sheet or static web pages.

[alancalverd]

depends on how long the accelerating force has been acting.

So, your conclusion that it won't roll is premature.

It can only roll if it makes sudden edge contact with the new surface and has sufficient kinetic energy to raise the center of mass through 0.7 m without sliding, so we need to know the coefficient of friction: more like a raised brick than a gravel path.

[alancalverd]

It is important for any standard to be consistent.

The standard is absolutely consistent.

A tangential force F applied at a distance r exerts a torque Fr. Everyone knows that.

At constant torque, say when rotating against constant friction, the work done is Frθ. Everyone knows that too.

The energy stored in a tightened clock spring is ∫Fr∂θ. Every watchmaker knows that.

[Bored chemist]

Now, in other case where there is no actual rotation, even so slightly, what is the radius of rotation that you will use to calculate torque?

It depends if I'm sat on the bench or stood next to it.

How do they make a difference?

Think about it.

Scratch.png (36.94 kB . 953x751 - viewed 326 times)

Will this very badly drawn person make the table rotate about the feet of the table on the floor behind him?

[alancalverd]

Looks very much like rowing on a sliding seat. Experimentally, both Oxford and Cambridge boats have indeed sunk, and on one occasion, both did so. But I think it was more to do with wind and tide than torque alone.

[hamdani yusuf (OP)]

depends on how long the accelerating force has been acting.

So, your conclusion that it won't roll is premature.

It can only roll if it makes sudden edge contact with the new surface and has sufficient kinetic energy to raise the center of mass through 0.7 m without sliding, so we need to know the coefficient of friction: more like a raised brick than a gravel path.

The center of mass is at the lowest point when the bottom of the box is flat to the floor. It's 0.5 m above the floor. At the highest point, is about 0.7 m. The increase is about 0.2 m.
It can still slides a bit while it starts to roll.
The torque is a combination of friction force by the floor and applied horizontal force on the top side. They are opposed by the gravitational force on the box.

[hamdani yusuf (OP)]

Will this very badly drawn person make the table rotate about the feet of the table on the floor behind him?

You can simply draw additional forces in this case. There will be a gravitational force down at the sitting position from the person's weight. An additional force as the reaction to the force applied to the wrench. It's equal in magnitude but opposite in direction.

[hamdani yusuf (OP)]

The standard is absolutely consistent.

Torque is defined as rotational counterpart of force.
F= m. a
τ= I. α
Let's check the consistency of current standards.
A torque 1 Nm =1 kg.m^2/s^2 is applied to stationary object with rotational inertia 1 kg.m^2
What is the angular acceleration?

If the torque is applied for 1 second,
What is the angular velocity then? What's the angular momentum?

[paul cotter]

Elementary physics- Stead.