[hamdani yusuf (OP)]

We know what a rad is, I used the term because you were using it. There is no angle in torque.

How do you measure the force? Can you do it without any change in position?
No matter how small it is, the change in position must be there in order for the fulcrum and the weight on the other side of the lever to produce reacting forces that oppose the acting force.

[hamdani yusuf (OP)]

Especially in levers, measuring radius is much easier than measuring the arc length or rotational angle.

I've mentioned in my other threads that rules are used with emphasis on practicality. On the other hand, standards are intended to maximize/prioritize consistency.

[hamdani yusuf (OP)]

To produce a purely rotational motion from a stationary object, at least two forces with opposite direction is needed. They also need to be not in line with each other.
Unopposed force will produce linear acceleration.

In the case of levers, people tend to ignore the normal force exerted by the fulcrum to the lever. Except when they need to assess the adequacy of it's strength.

[hamdani yusuf (OP)]

Especially in levers, measuring radius is much easier than measuring the arc length or rotational angle.

I've mentioned in my other threads that rules are used with emphasis on practicality. On the other hand, standards are intended to maximize/prioritize consistency.

When Archimedes described how levers work, he didn't seem to care much about the consistency of units among rotational quantities. He just wanted to use it for designing levers that work.

[alancalverd]

How do you measure the force? Can you do it without any change in position?

If the torque axis is horizontal, just hang a known weight on the end of the lever. For any other orientation, use a spring balance.

[hamdani yusuf (OP)]

How do you measure the force? Can you do it without any change in position?

If the torque axis is horizontal, just hang a known weight on the end of the lever. For any other orientation, use a spring balance.

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

No matter how small it is, the change in position must be there in order for the fulcrum and the weight on the other side of the lever to produce reacting forces that oppose the acting force.

[hamdani yusuf (OP)]

Q What's the unit of Torque?
A The  unit of torque is mass* length squared / time squared

(Not sure this needed a thread)

Your answer makes me sure that we need this thread.
Let's have a simpler case for illustration.
An elevator motor drives a 1 meter radius pulley to lift 1 Newton of weight. After a brief momentary initial kick, a constant torque is applied which lifts the weight at 1 mm/s constant speed. A thousand seconds later, the motor stops and the weight has been elevated by 1 m from initial position. The work done to the weight is 1 Joule. The rotation angle is 1 radian.
The second case, the motor doesn't stop until 2000 seconds from initial kick. With the same torque and lifting speed, the weight has been elevated by 2 m from initial position. The work done to the weight is 2 Joule. The rotation angle is 2 radian.

In the first case, 1 Joule of energy is used to rotate the pulley system by 1 radian, while In the second case, 2 Joule of energy is used to rotate the pulley system by 2 radian. In both case, the torque is the same, i.e. 1 Joule/radian.

So what?

Get back to me if this stops being true.

The  unit of torque is mass* length squared / time squared

Mass, length, and time are not units. They are dimensions.

[paul cotter]

As others and I have repeatedly said torque can exist without rotation, therefore the angle is not an intrinsic component of torque- the angle comes into play when rotation has occurred and the energy expended can be calculated. 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. PS: in your example on #226 you state that the "torque is the same, ie  1joule/radian". This is wrong as it gives the energy per radian. Torque does not have the dimensions of energy.

[Bored chemist]

Have you tried Gemini advanced?

I used the one you said gave the right answer.

I asked Gemini, ...

[hamdani yusuf (OP)]

In linear motion, F=m.a
Analogous for angular motion,
τ = I.α
Unit of angle must be explicitly stated in α. Why shouldn't it in the other quantities?

What would happen if the unit of angle is discarded from angular acceleration?
It stops being angular acceleration.
Thus if you want to eliminate angle of rotation from the unit of torque, the unit of rotational inertia must contain inverse of rotational angle in order to cancel out the unit of rotational angle from angular acceleration.

[hamdani yusuf (OP)]

As others and I have repeatedly said torque can exist without rotation, therefore the angle is not an intrinsic component of torque- the angle comes into play when rotation has occurred and the energy expended can be calculated.

Repeatedly saying the wrong things doesn't make them any more true.
Without rotation, net torque must be zero.

[paul cotter]

You are confusing force and motion.

[paul cotter]

"without rotation torque must be zero"? Not according to anyone who has tried to shift a frozen bolt. Anyway this has degenerated into another pointless hopeless argument bedevilled by utter confusion and i'm out.

[hamdani yusuf (OP)]

In linear motion, F=m.a
Analogous for angular motion,
τ = I.α
Unit of angle must be explicitly stated in α. Why shouldn't it in the other quantities?

What happens if unit of angle is discarded from angular acceleration?
 It stops being angular acceleration.
If you insist on eliminating unit of rotational angle from torque, you'll need to cancel it out by using inverse of rotational angle for unit of rotational inertia. Either way, you're losing consistency among units of rotational quantities.

[hamdani yusuf (OP)]

You are confusing force and motion.

F= m.a
If a=0, F=0
This is a basic math.
In rotational motion,
τ = I.α
If α=0,  τ = 0

[hamdani yusuf (OP)]

"without rotation torque must be zero"? Not according to anyone who has tried to shift a frozen bolt. Anyway this has degenerated into another pointless hopeless argument bedevilled by utter confusion and i'm out.

You are repeating Alan's confusion.

Without rotation, net torque must be zero.

You can come back again when you have a better understanding of the basic concepts of rotational systems.

[hamdani yusuf (OP)]

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)

[hamdani yusuf (OP)]

Let's analyze a thought experiment. A wooden cubic box measured 1x1x1 meter, weight 100kg is on a smooth slippery floor. A force 100 N is applied horizontally to its top side. Consequently, the box move sideways.

After a few meters of translation the floor gets rough, producing higher friction. The box starts to roll.

In the first case, the torque is zero, because it doesn't cause rotation. While in the second case it's not zero, even though the force applied to the top of the box doesn't change.

[alancalverd]

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.

[alancalverd]

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)