I Light in an accelerated elevator

[John Mcrain]

Elevator (2m height) is accelerate upward, light is at the top pointed toward flor of elevator.
Is time t=2m/c to light pass from top to bottom?

Bottom moving toward light,so time would be smaller then t=2m/c?

 

[Dale]

Bottom moving toward light,so time would be smaller then t=2m/c?

In an inertial frame, yes.

 

[John Mcrain]

In an inertial frame, yes.

How explain smaller t, c increase(impossible), elevator become shorter then 2m ?

In frame of elevator t is also smaller then t=2m/c, once when light leave top it is not part of elevator and flor coming toward light?

 

[Ibix]

How explain smaller t, c increase(impossible), elevator become shorter then 2m ?

The speed of light is only invariant in inertial frames of reference. It can differ in other classes of frame.

I'm not sure who is measuring what in your scenario, so it's difficult to know how to answer exactly. But note that, as measured in an inertial frame, the rate of a clock in the lift is varying, as is the length of the lift. This will have consequences for the speed of light as measured by an observer in the lift.

 

[Dale]

How explain smaller t, c increase(impossible), elevator become shorter then 2m ?

Obviously, the explanation is that the elevator is moving in the inertial frame. You already gave that explanation in your OP so I am not sure why you seem to be ignoring your own statements now.

In frame of elevator

Before you ask any questions about the frame of the elevator you will need to define what you mean. Common choices would be Kottler Moeller, Rindler, or Lass coordinates.

See https://en.m.wikipedia.org/wiki/Rindler_coordinates

Once you choose the coordinates you choose to represent the frame of the elevator then the remainder of your questions can be answered

 

[John Mcrain]

Obviously, the explanation is that the elevator is moving in the inertial frame. You already gave that explanation in your OP so I am not sure why you seem to be ignoring your own statements now.

Before you ask any questions about the frame of the elevator you will need to define what you mean. Common choices would be Kottler Moeller, Rindler, or Lass coordinates.

See https://en.m.wikipedia.org/wiki/Rindler_coordinates

Once you choose the coordinates you choose to represent the frame of the elevator then the remainder of your questions can be answered

So I cant use same formulas as instead light is ball?

 

[John Mcrain]

The speed of light is only invariant in inertial frames of reference. It can differ in other classes of frame.

I'm not sure who is measuring what in your scenario, so it's difficult to know how to answer exactly. But note that, as measured in an inertial frame, the rate of a clock in the lift is varying, as is the length of the lift. This will have consequences for the speed of light as measured by an observer in the lift.

light can be faster then c in non inertial frame?

Men in elevator meassure with stopwatch how long take the light to hit the flor.

 

[Dale]

So I cant use same formulas as instead light is ball?

Not if you want it to be relativistically correct. Of course, if you just want a rough approximation then that would be fine.

light can be faster then c in non inertial frame?

Yes

Men in elevator meassure with stopwatch how long take the light to hit the flor.

You still have to choose your coordinates for that.

 

[John Mcrain]

Of course, if you just want a rough approximation then that would be fine.

Ball in my video has a=10m/s2, what is acceleration of light?

 

[Dale]

Ball in my video has a=10m/s2, what acceleration I must use for light?

The problem is not the value of $a$. You have to choose a coordinate system for the accelerated frame to get relativistically accurate results.

Why are you so resistant to making this choice?

 

[John Mcrain]

The problem is not the value of $a$. You have to choose a coordinate system for the accelerated frame to get relativistically accurate results.

Why are you so resistant to making this choice?

I ask for non relativistic case, case where I use formula as in my video with ball

 

[Ibix]

I ask for non relativistic case, case where I use formula as in my video with ball

The problem with that is that you don't have a static situation. If the proper acceleration doesn't vary along the height of the lift then the length of the lift is varying in its own rest frame. And you still need to choose what coordinates to work in, because you can't avoid relativity when you are asking about light.

The point that @Dale is making is that the answer you will get depends on the choice of coordinate system you choose. You don't know which to choose because you don't have a practical reason for doing the analysis, so there's no particular advantage to one over another. So flip a coin or whatever and pick one.

 

[John Mcrain]

And you still need to choose what coordinates to work in, because you can't avoid relativity when you are asking about light.

That mean I cant use formula from my video with ball.

 

[Dale]

I ask for non relativistic case, case where I use formula as in my video with ball

For a non relativistic case you can use the approach in the video, but that would be best in a different sub forum. The relativity sub forum is for relativity

 

[Ibix]

The relativity sub forum is for relativity

To be fair, this is in Classical. But it's relativity anyway if we need to discuss light in accelerating frames.

 

[Dale]

To be fair, this is in Classical. But it's relativity anyway if we need to discuss light in accelerating frames.

Oops, that’s embarrassing.

@John Mcrain please decide if you want to discuss balls or light. If you want to discuss light then I will move this to the relativity forum. If you want to discuss balls then I will close this thread and you can start a new one focused on balls.

 

[John Mcrain]

For a non relativistic case you can use the approach in the video,

How can I use this approach for light, if I dont know what is acceleration of light?

@John Mcrain please decide if you want to discuss balls or light. If you want to discuss light then I will move this to the relativity forum. If you want to discuss balls then I will close this thread and you can start a new one focused on balls.

I didnt know when I write my first post that belong to relativity..I think I wont go to relativity forum for now, it is too complicated..
And with ball answer is in my video...

 

[Dale]

How can I use this approach for light

You cannot. Balls are non relativistic. Light is the most relativistic thing there is.

I think I wont go to relativity forum for now, it is too complicated..
And with ball answer is in my video...

Sounds good. I will close the thread then. When you are ready to discuss light please post in the relativity sub forum.