Torque & Joules: Fact or Fiction?

[Entanglement]

Wikipedia says that the unit of magnetic dipole moments is calculated by Joule/B that means that the torque is measured by joules
I really doubt that, it seems non sense.

 

[Doc Al]

Wikipedia says that the unit of magnetic dipole moments is calculated by Joule/B that means that the torque is measured by joules
I really doubt that, it seems non sense.

Torque has units of Force*distance. Usually expressed as N-m, but equivalent to Joules though I do not recommend that usage. (Usually Joule is reserved for energy, not torque!)

 

[Entanglement]

But equivalent to Joules though!

How is that ?

 

[Entanglement]

Energy equals the product of the force and the displacement along which the force is done

And the torque is the product of the force and displacement between the two forces, the concept of displacement isn't the same in both cases

 

[Doc Al]

How is that ?

1 N-m = 1 J

 

[Doc Al]

Energy equals the product of force and the displacement

And torque is product of force and displacement between the two forces the " d " isn't the same in both cases

We are talking about units, not about the definitions of torque and energy. (That's why energy is Joules while torque is in N-m, despite the fact the units are equivalent.)

 

[Entanglement]

The units are are the same but their definitions are different

 

[Doc Al]

Read this discussion of the units for torque: http://en.wikipedia.org/wiki/Torque#Units

 

[Doc Al]

The units are are the same but their definitions are different

Right. (For example, one is a vector while the other is a scalar.)

 

[Entanglement]

But I think that it's totally wrong to say that torque is measured by joules not just "unrecommended"

 

[Entanglement]

Thanks jersey

 

[adjacent]

jersey?

 

[russ_watters]

Wikipedia says that the unit of magnetic dipole moments is calculated by Joule/B that means that the torque is measured by joules
I really doubt that, it seems non sense.

I'm not seeing that (I'm seeing n-m), can you link and quote it please.

 

[UltrafastPED]

I see n-m/T ... Newton-meters per Tesla, but this is not torque; it is the magnetic moment.
http://en.wikipedia.org/wiki/Magnetic_moment#Units

 

[Entanglement]

I see n-m/T ... Newton-meters per Tesla, but this is not torque; it is the magnetic moment.
http://en.wikipedia.org/wiki/Magnetic_moment#Units

After that is says Joule/tesla

 

[Entanglement]

http://en.m.wikipedia.org/wiki/Magnetic_moment

Anyway, I got it, no problem

 

[Entanglement]

 

[Entanglement]

However, how is work done by a torque calculated ??

I know that work is calculated by f.d
I'm unable to apply that on non linear motion

 

[jtbell]

What is the equivalent of "distance" if something rotates instead of moving along a line?

 

[BiGyElLoWhAt]

What is the equivalent of "distance" if something rotates instead of moving along a line?

Angular displacement i.e. Radians

Spoiler

KE_{angular} = \frac{1}{2}I\omega ^2

 

[BiGyElLoWhAt]

However, how is work done by a torque calculated ??

I know that work is calculated by f.d
I'm unable to apply that on non linear motion

Linear motion:

Spoiler

$W = \int_{a}^{b}\vec{F} (dot)d\vec{r}$

Angular motion:

Spoiler

$W = \int_{a}^{b}\vec{T}(dot)d\vec{\theta}$

 

[BiGyElLoWhAt]

Oh wait, you were leading them on... @jtBell consider them edited

 

[Entanglement]

Torque.theta ??

Theta is radian ?

Can you tell me the proof of that law??

 

[Entanglement]

What is the equivalent of "distance" if something rotates instead of moving along a line?

Shouldn't it be radian.radius ??

 

[A.T.]

Torque.theta ??

Theta is radian ?

Can you tell me the proof of that law??

Convert the linear work done by a tangential force along the circumference to torque the force produces around the center and angle the point of attack travels.

 

[Dadface]

This point was raised as a short question in an A level physics paper of years ago:

Torque can be measured in Joules but it is usually considered misleading to do so. Explain why? (I don't remember the exact wording)

 

[Entanglement]

This point was raised as a short question in an A level physics paper of years ago:
Torque can be measured in Joules but it is usually considered misleading to do so. Explain why? (I don't remember the exact wording)

Because the definition of d is different in case of torque and energy

Torque = f.d
Where d is the displacement between the two forces

Energy = f.d
Where d is the displacement along which the force is done

 

[A.T.]

Torque = f.d
Where d is the displacement between the two forces

Torque doesn't require two forces.

 

[Entanglement]

Torque doesn't require two forces.

Even if it is a rotating coil ??

 

[A.T.]

Even if it is a rotating coil ??

There is only one force in the definition of torque. So what "two forces" are you taking about?

 

[Entanglement]

There is only one force in the definition of torque. So what "two forces" are you taking about?

I only studied torque in electromagnetism, what I know about is that when two equal forces opposite in direction and have different line of actions act on a coil, it's affected by a torque.

 

[adjacent]

I only studied torque in electromagnetism, what I know about is that when two equal forces opposite in direction and have different line of actions act on a coil, it's affected by a torque.

Haven't you studied this?

 

[Entanglement]

Haven't you studied this?

No, I didn't study Torque in a mechanics class, it was a physics class and specifically in electromagnetism.

 

[Doc Al]

I only studied torque in electromagnetism, what I know about is that when two equal forces opposite in direction and have different line of actions act on a coil, it's affected by a torque.

You are thinking of a couple, where two forces are used to create a torque without producing a net force. See: http://en.wikipedia.org/wiki/Couple_(mechanics)

 

[Entanglement]

You are thinking of a couple, where two forces are used to create a torque without producing a net force. See: http://en.wikipedia.org/wiki/Couple_(mechanics)

Thanks

 

[Entanglement]

You are thinking of a couple, where two forces are used to create a torque without producing a net force. See: http://en.wikipedia.org/wiki/Couple_(mechanics)

Is the energy done by a couple is equal to zero ?

 

[adjacent]

Is the energy done by a couple is equal to zero ?

Why should it be zero?
If the rod starts rotating,it gains rotational kinetic energy.

 

[Entanglement]

Why should it be zero?

If the rod starts rotating,it gains rotational kinetic energy.

I have no idea about rotational mechanics, linear only.

 

[Vanadium 50]

I have no idea about rotational mechanics, linear only.

You will have a very difficult time understanding toque thinking only about linear mechanics.