0 Members and 1 Guest are viewing this topic.

is proper acceleration absolute?

Let us discuss.

Hi again. * The points A_{i} don't seem to have been given the correct co-ordinates to match the diagram. * K_{1}' and K_{2}' don't seem to be related to the curved yellow lines in the second diagram. * The table of values at the end is difficult to understand. In the first column, some radius r is changing. What or where is that r? I'm trying to see what you wanted to discuss but I'm still not sure at the moment, sorry.Best Wishes.

Hi. OK, I can see what you've got know. Rigid body dynamics with an embedded body frame. I'm guessing the point B was the centre of mass of your body.....Best Wishes.

In relativity theory, proper acceleration is the physical acceleration (i.e., measurable acceleration as by an accelerometer) experienced by an object.

...Then if by "absolute" you mean "would be agreed by all observers" the answer is clearly yes, provided that you don't demand simultaneity of observation. ...

Yet, the calculations show all inertial observes do not agree on the acceleration.Different inertial observers predict different accelerations based on the textbook calculations.

the data the rocket transmits is absolute acceleration, force per unit mass

Fair enough, because what they see is relative acceleration, i.e. the apparent second derivative of position versus time of an object viewed from a distance, but the data the rocket transmits is absolute acceleration, force per unit mass.

So a massless body cannot experience that kind of acceleration?

Hi.Quote from: Jaaanosik on 09/04/2023 15:16:27Yet, the calculations show all inertial observes do not agree on the acceleration.Different inertial observers predict different accelerations based on the textbook calculations. I'm still not following, sorry.You have a formula for the acceleration at point A. All of the things in that formula are determined with reference to the frame K and not K1' or K2'. To get the acceleration with respect to a frame, let's say centred at O at time t=0 and with the offset velocities you have specified, then you still have some work to do. It's not a lot of work, for Galilean relativity or non-relativistic mechanics, the accelerations in those frames are identical to those in the frame K. Under special relativity, a proper acceleration must, by definition, be measured in the frame where the individual (Sally) was instantaneously at rest. It will not be the same as an acceleration that someone else (Huang) might assign to Sally in the frame where Huang was at rest (unless Huang and Sally were at rest with respect to each other).Best Wishes.(Overlap with @alancalverd, who posted before I finished. Looks OK and consistent).

Hi.Quote from: geordief on 09/04/2023 17:21:07So a massless body cannot experience that kind of acceleration? Being massless has made it considerably more complicated. I think you ( @geordief) need to bring that down to specific examples rather than discussing the situation in general. We would then select a more appropriate system of mechanics that can be applied (e.g. General Relativity). With simple Newtonian mechanics, a massless body has no inertia or resistance to any force that you think you could apply to it. However, there's no reason to assume it can have any force act on it, all accelerations are possible even without any force. Overall, Newtonian mechanics just will not handle a massless particle.Best Wishes.

If you are willing, please, show your calculation they are equal, we can compare.

As the subject says, is proper acceleration absolute?The answer is yes, because all inertial observers agree on the acceleration that would be measured by an accelerometer.

Correct, these are straight textbook calculations that are the subject of the discussion.

The different inertial observers do not agree on the acceleration.

K'1 moves with speed 1m/s in +X direction in the rest frame K, sees the top of the cycloid.K'2 moves with speed 1m/s in -X direction in the rest frame K, sees the cusp of the cycloid.

Yet, the calculations show all inertial observes do not agree on the acceleration.

To get the acceleration with respect to a frame,

Is there anything wrong with the analysis?

Did somebody find an error or mistake?

I agree, the claim the acceleration analysis done here breaks the relativity as we know it, that's a new hypothesis. The relativity cannot work unless it is done through a preferred reference frame.

Is there a physicist who can show the analysis is not good?

An observer not undergoing the acceleration in question would likely compute the proper acceleration of said thing in question and not 'observe' it.