Light speed using circumference

[3118beach]

Trying to get my mind around this if you had a motorised arm that was capable of spinning an object 100mm from it's centre at 3000 kmh how long would that arm have to be for the object at the tip of it to be travelling light speed?

[mathematic]

R=100mm x (speed of light)/3000kmh.  Speed of light in kmh.  Main problem, relativistic effect would prevent it.

[swansont]

It can't move at light speed, so in a sense it's a trick question.

[Vmedvil]

Well, if you did reach the speed of light the relativistic mass would be so large it would turn into a blackhole wrap your mind around that.

[Strange]

4 minutes ago, Vmedvil said:

Well, if you did reach the speed of light the relativistic mass would be so large it would turn into a blackhole wrap your mind around that.

Doesn't work like that. (After all, in the frame of reference of the object, there is no mass increase so it can't turn into a black hole.)

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_fast.html

[Vmedvil]

8 minutes ago, Strange said:

Doesn't work like that. (After all, in the frame of reference of the object, there is no mass increase so it can't turn into a black hole.)

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_fast.html

I had no idea strange, I thought the relativistic mass increase would do it eventually. 

Edited November 27, 2017 by Vmedvil

[swansont]

10 hours ago, Strange said:

Doesn't work like that. (After all, in the frame of reference of the object, there is no mass increase so it can't turn into a black hole.)

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_fast.html

You would have to add energy for this to happen — it's not a matter of changing reference frames. It's a rotational system. The rotational KE does increase the mass, according to an inertial frame observer (e.g. in the frame of the rotational axis)

[Vmedvil]

52 minutes ago, swansont said:

You would have to add energy for this to happen — it's not a matter of changing reference frames. It's a rotational system. The rotational KE does increase the mass, according to an inertial frame observer (e.g. in the frame of the rotational axis)

Ya, see thats kinda what I thought too, wouldn't an increased Relativistic mass, increase gravitational potential energy.

One can also say that, averaged over all directions, the tidal gravity increases when an object moves. ... Note that in General Relativity, gravity is caused not by mass, but by the stress–energy tensor. Thus, saying that a moving particle has "more gravity" does not imply that the particle has "more mass".

But, it has more of both in this case, Energy and Relativistic Mass near or at the speed of light.

17 hours ago, 3118beach said:

Trying to get my mind around this if you had a motorised arm that was capable of spinning an object 100mm from it's centre at 3000 kmh how long would that arm have to be for the object at the tip of it to be travelling light speed?

Where this is flawed logic you need an acceleration to generate energy it would stay constant @ 3000 kmh as you need an acceleration to transfer energy as

E = Δx a M

E = Energy

Δx or R = Distance

a = Acceleration

M = Mass

Not velocity, but acceleration, which Km / h  is velocity.

The acceleration here in toward the middle frame, thus energy is transferring toward the center of rotation frame not the spin frame.

Edited November 27, 2017 by Vmedvil

[studiot]

45 minutes ago, Vmedvil said:

wouldn't an increased Relativistic mass, increase gravitational potential energy.

You always require at least two objects to generate a potential.

[swansont]

47 minutes ago, Vmedvil said:

Ya, see thats kinda what I thought too, wouldn't an increased Relativistic mass, increase gravitational potential energy.

The thing is, it's not relativistic mass. If it was relativistic mass, then Strange's objection would be valid, but so-called relativistic mass comes from including translational KE. This device's COM is not translating.

 

47 minutes ago, Vmedvil said:

One can also say that, averaged over all directions, the tidal gravity increases when an object moves. ... Note that in General Relativity, gravity is caused not by mass, but by the stress–energy tensor. Thus, saying that a moving particle has "more gravity" does not imply that the particle has "more mass".

This isn't a "moving particle" 

 

[Vmedvil]

37 minutes ago, swansont said:

The thing is, it's not relativistic mass. If it was relativistic mass, then Strange's objection would be valid, but so-called relativistic mass comes from including translational KE. This device's COM is not translating.

 

This isn't a "moving particle" 

 

Yes, but it constructed of particles at some point you hit Up and Down quarks along with electrons due to "Hydrostatic" stress on the space and it is being directed toward the "Hydrostatic" axis remember GR views energy as a Perfect fluid.

41 minutes ago, studiot said:

You always require at least two objects to generate a potential.

The "Hydrostatic" Stress by the energy acts as a second object, which could be said to be not different than the effect of mass on that space.

Edited November 27, 2017 by Vmedvil

[swansont]

9 minutes ago, Vmedvil said:

Yes, but it constructed of particles at some point you hit Up and Down quarks along with electrons due to stress on the space.

If this made any sense I'd most likely disagree with it.

 

E²=p²c² + m²c⁴

p is the linear momentum. All translation motion shows up in that term. Anything that's not translation CoM motion shows up in the mass term, including rotation and vibration.

It's when you try to say that E = mc² applies to all conditions, you're including the translational KE.  

 

[Vmedvil]

34 minutes ago, swansont said:

If this made any sense I'd most likely disagree with it.

 

E²=p²c² + m²c⁴

p is the linear momentum. All translation motion shows up in that term. Anything that's not translation CoM motion shows up in the mass term, including rotation and vibration.

It's when you try to say that E = mc² applies to all conditions, you're including the translational KE.  

 

What is rest mass?, it is the mass of these particles rest energy which is E = MC²   , pC is KE or that.

Edited November 27, 2017 by Vmedvil

[studiot]

41 minutes ago, Vmedvil said:

Yes, but it constructed of particles at some point you hit Up and Down quarks along with electrons due to "Hydrostatic" stress on the space and it is being directed toward the "Hydrostatic" axis remember GR views energy as a Perfect fluid.

The "Hydrostatic" Stress by the energy acts as a second object, which could be said to be not different than the effect of mass on that space.

 

 

You have two objects in your diagram.

Either side of the free body diagram, because both objects are contained within the same body.

 

[Vmedvil]

2 minutes ago, studiot said:

 

 

You have two objects in your diagram.

Either side of the free body diagram, because both objects are contained within the same body.

 

Yes, but the stress is not within the same body look at the direction of a_c and p.

Edited November 27, 2017 by Vmedvil

[Strange]

10 minutes ago, swansont said:

E²=p²c² + m²c⁴

p is the linear momentum. All translation motion shows up in that term. Anything that's not translation CoM motion shows up in the mass term, including rotation and vibration.

I did wonder about the rotational aspect when I made my comment. So are you saying that an object can rotate fast enough to turn into a black hole? This seems reasonable (I am reminded of another thread where it was pointed out that the time dilation of an object in a centrifuge could be described equivalently as either a gravitational effect or in terms of [rotational]speed.)

[Vmedvil]

7 minutes ago, Strange said:

I did wonder about the rotational aspect when I made my comment. So are you saying that an object can rotate fast enough to turn into a black hole? This seems reasonable (I am reminded of another thread where it was pointed out that the time dilation of an object in a centrifuge could be described equivalently as either a gravitational effect or in terms of [rotational]speed.)

Well, it would turn the center of rotation into the BH because of the pC term.

Edited November 27, 2017 by Vmedvil

[studiot]

14 minutes ago, Vmedvil said:

Yes, but the stress is not within the same body look at the direction of a_c and p.

So you have at least two objects.

 

[Vmedvil]

10 minutes ago, studiot said:

So you have at least two objects.

 

Yes the Rest Mass which is bound at every point within the Fermions and the Energy-Stress or Relativistic mass which is not.

Edited November 27, 2017 by Vmedvil

[swansont]

30 minutes ago, Strange said:

I did wonder about the rotational aspect when I made my comment. So are you saying that an object can rotate fast enough to turn into a black hole? This seems reasonable

Yes it can. All inertial observers will agree that it's spinning — that's not relative. An excited-state atom has more mass than the ground state, as does a spinning vs stationary top, or hot vs cold bucket of water. (and none of that invokes relativistic mass)

30 minutes ago, Strange said:

(I am reminded of another thread where it was pointed out that the time dilation of an object in a centrifuge could be described equivalently as either a gravitational effect or in terms of [rotational]speed.)

I may have been the one who pointed it out. People did a follow-up of the Pound-Rebka experiment with a centrifuge. You can solve for the time dilation with SR or with a pseudo-potential and GR. Looks exactly the same.

 

28 minutes ago, Vmedvil said:

Well, it would turn the center of rotation into the BH because of the pC term.

p = 0 for that system

[Vmedvil]

3 minutes ago, swansont said:

Yes it can. All inertial observers will agree that it's spinning — that's not relative. An excited-state atom has more mass than the ground state, as does a spinning vs stationary top, or hot vs cold bucket of water. (and none of that invokes relativistic mass)

I may have been the one who pointed it out. People did a follow-up of the Pound-Rebka experiment with a centrifuge. You can solve for the time dilation with SR or with a pseudo-potential and GR. Looks exactly the same.

 

p = 0 for that system

then it is just rest mass, then why is it moving if p = 0

Edited November 27, 2017 by Vmedvil

[swansont]

Just now, Vmedvil said:

then it is just rest mass, then why is it moving if p = 0

It's rotating. Rotational motion and linear motion are not the same thing. A spinning wheel has no linear momentum, but it has angular momentum.

[Vmedvil]

11 minutes ago, swansont said:

It's rotating. Rotational motion and linear motion are not the same thing. A spinning wheel has no linear momentum, but it has angular momentum.

Is it really different besides being over a radius?

Edited November 27, 2017 by Vmedvil

[Strange]

8 minutes ago, swansont said:

Yes it can. All inertial observers will agree that it's spinning — that's not relative. An excited-state atom has more mass than the ground state, as does a spinning vs stationary top, or hot vs cold bucket of water. (and none of that invokes relativistic mass)

I knew ... uh, should have known ... that.

I guess the hot water example can be described in terms of the increased kinetic energy of the molecules but the net momentum is, again, zero so all observers will agree on the energy increase.

[studiot]

10 minutes ago, Vmedvil said:

Is it really different besides being over a radius?

Yes in the linear case there need be no acceleration.

In the rotating case you cant do without it.