Groups > sci.physics > #520624

Re: Relativistic Radio

From	Poutnik <poutnik4nntp@gmail.com>
Newsgroups	sci.physics
Subject	Re: Relativistic Radio
Date	2015-09-13 08:35 +0200
Organization	Good company
Message-ID	<mt35ci$lbc$1@dont-email.me> (permalink)
References	(10 earlier) <msusen$m3$1@dont-email.me> <msuv3d$bom$1@speranza.aioe.org> <6eb355ae-0ce9-4a02-8cf3-bdbacba8a07b@googlegroups.com> <mt2bkn$nmt$1@dont-email.me> <0733dab1-fdab-43ae-8d06-113152095cd8@googlegroups.com>

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Dne 13/09/2015 v 08:09 jaymoseley@hotmail.com napsal(a):
> Poutnik wrote...
>> In the frame where the ball ejector is still, the ball gains kinetic energy 1/2 . m . x^2.
>> In the frame where the ball ejector moves by speed y, the ball gains kinetic energy 1/2 . m . [(x+y)^2 - y^2] = 1/2 . m . [x^2 + 2.x.y], having initially already >energy 1/2 . m . y^2 and finally energy 1/2 . m . (x+y)^2.
> 
> In your first example above where the ball ejector is still you have the ball gaining
> kinetic energy 1/2.m.x^2. 

> But you forgot to take into account the fact that the target is moving towards
> the ball ejector at speed y in this example. Therefore ball hits the moving target 
> at speed x+y . Not at speed x 

No, I did not. You confuse speed and closing speed.
Speed of the ball is x, while closing speed bass vs target is x+y.
Kinetic energy of an object is defined by its speed,
not by its closing speed wrt other object.

> So shouldnt the calculation for the first example  be the same as the second example?
>  Ie... 1/2 . m . (x+y)^2.

No, it should not. The ball energy in the still ejector case
is 1/2 . m . x^2.


> The important speed is not how fast the ball moves relative to the ejector, but
> rather how fast it hits the target. 

It is the same, unless there is acceleration, what is not the case.
Both are the same quantity, closing speed ball vs target.

Speed is how fast an object move wrt a frame.
Closing speed is how fast an object moves wrt other object.
If the other object is coincidentally still in the frame,
both quantities are numerically equal.

The difference is both frames is, that in  the still ejector case,
energy released at collision comes from both the ball and target,
while in the still target case
all the collision energy comes from the ball.

Also, in both frames the objects have different energy after collision.


-- 
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.

Thread

Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-06 20:21 +0000
  Re: Relativistic Radio Double-A <double-a3@hush.com> - 2015-09-06 14:34 -0700
    Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-06 21:47 +0000
  Re: Relativistic Radio pcardinale@volcanomail.com - 2015-09-06 17:36 -0700
    Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-07 01:56 +0000
      Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-07 07:15 +0200
        Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-07 05:44 +0000
          Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-07 08:50 +0200
      Re: Relativistic Radio pcardinale@volcanomail.com - 2015-09-07 15:16 -0700
      Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-08 10:04 -0500
        Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-08 16:59 +0000
          Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-08 12:41 -0500
            Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-08 18:24 +0000
          Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-08 21:22 +0200
        Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-08 17:43 +0000
          Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-08 12:47 -0500
            Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-08 19:26 +0000
        Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-10 01:58 -0700
          Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-10 19:16 +0200
            Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-10 19:42 +0200
              Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-11 00:53 -0700
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-11 06:07 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-11 15:08 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-11 15:28 +0200
                Re: Relativistic Radio Mahipal <mahipal7638@gmail.com> - 2015-09-11 06:31 -0700
                Re: Relativistic Radio "Phony McNymster" <invalid@example.com> - 2015-09-11 07:42 -0700
                Re: Relativistic Radio Mahipal <mahipal7638@gmail.com> - 2015-09-11 07:59 -0700
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-11 07:16 -0700
                Re: Relativistic Radio Sam Wormley <swormley1@gmail.com> - 2015-09-11 09:41 -0500
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-11 09:49 -0500
                Re: Relativistic Radio Fabian Russell <root@localhost.localdomain> - 2015-09-11 18:18 +0000
                Re: Relativistic Radio noTthaTguY <abu.kuanysh05@gmail.com> - 2015-09-11 11:24 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-12 11:20 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-12 06:21 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 02:04 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-13 00:07 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 09:22 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 09:59 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-13 03:44 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-14 07:33 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-14 07:49 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 01:07 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 10:40 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 03:40 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 13:19 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 04:55 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 15:01 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 16:36 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 12:18 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 08:29 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 02:41 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 12:11 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 06:06 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 15:40 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 06:06 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 15:59 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 09:39 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 18:47 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 10:10 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 19:57 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 11:14 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 20:23 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 20:31 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 12:21 -0700
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-15 13:30 -0500
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 00:57 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 14:50 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 12:57 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 08:37 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 03:06 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 13:10 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 13:15 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-15 06:43 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 16:11 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 18:26 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 18:35 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 16:44 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-14 08:15 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-14 08:44 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-11 17:38 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-11 18:00 +0200
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-11 11:22 -0500
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-12 12:29 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 01:16 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-12 23:09 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 08:35 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 08:44 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-12 23:50 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 09:14 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-13 05:24 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-14 07:35 +0200
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 01:01 -0700
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-14 10:39 +0200
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-14 09:34 -0500
                Re: Relativistic Radio jaymoseley@hotmail.com - 2015-09-14 12:31 -0700
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-15 08:53 +0200
                Re: Relativistic Radio Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-15 10:22 +0200
                Re: Relativistic Radio Poutnik <poutnik4nntp@gmail.com> - 2015-09-13 09:08 +0200
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-14 09:32 -0500
                Re: Relativistic Radio Odd Bodkin <bodkinodd@gmail.com> - 2015-09-14 09:31 -0500

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