Re: The opposing rockets and the box

"Spaceman" <spaceman@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:-uCdnd3r6cJyxhrVnZ2dnUVZ_u6dnZ2d@xxxxxxxxxxx
PD wrote:
On Jul 23, 12:39 am, "Spaceman" <space...@xxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
PD wrote:
On Jul 23, 12:11 am, "Spaceman"
<space...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Greg Neill wrote:
Is this another one of your trolls where you know
that what you are saying is nonsense, or are you
genuinely wrong? Inquiring minds want to know...

Greg, please do show us why Kinetic Energy is not conserved
Can you give an example?

Sure. Toss a ball vertically upward. Over the next few seconds,
it's going to lose all of its kinetic energy, to the point where
it is momentarily *stopped*, having no kinetic energy left at all.
Where did all that kinetic energy of the ball go on the way up?
Well, it goes *somewhere* because it gets it all back on the way
down. But where was it in the meantime? Just hiding? Saying, "you
can't see me!"?

So wait, you can stop in the middle of a motion and
just say the energy is now zero?
Wow!
That is amazing.
Oh wait.
The kinetic energy returns to it?
Hmm? where id it come from?
The magical gravity that "did not take it away" to begin with
or maybe gravity that did take it away to begin with.

Yes, quite possibly gravity that took it away. And while it took it
away, it was no longer kinetic energy, was it?

You tell me,
What storage device kept it "stored"

Gravitational potential.

Can you prove it is not there at all?

Yes, the ball was not moving, therefore zero kinetic energy.

If you prove it is not there at all, why does it start to fall again.

Gravity.

And then gain the same amount back?

Gravity is a conservative field.

If it is not "conservered" shouldn't it not have the same amount
when it comes back?

If kinetic energy is conserved then it *must* have the
same value at all times. It doesn't, so it's not.



Energy conservation says the amount stays *constant*. That means the
same number all all instants, not just at the beginning and the end.

The number don't stay "constant" when a battery goes dead.

Electric potential is not kinetic energy.

"the amount" is never in fact "constant.
It charges by gaining "numbers" and then gets released
by losing "numbers" with the end result beign the sames.
So you thought of energy "staying constant" is flawed.

Batteries trade energy types. Chemical potential
versus electric potential. Electric potential can
be made to do work, too, changing to heat or kinetic
energy. The grand total may be constant, but any
given one of them is not. Contrast this with
momentum which is *always* conserved, and never gets
traded with other things.


Energy conservation says that you can take *any* two moments of your
choosing and the amount will be the same in both. I chose two moments
where the amount of kinetic energy is different, and *kinetic* energy
is not conserved.

2 minutes into the charge of the battery and 10 minutes charge time
are not the same, again your "any" two moment thoughts are also
flawed.

Sorry, but PD never claimed that stored electrical energy
was constant.

I chose 2 "moments" when the energy was different.

Bully for you. Too bad it's not a relevant example.




The *total* energy is conserved, however, because
some of that *kinetic* energy is converted to *gravitational
potential* energy, which is not kinetic energy at all. Would you like
a link where you can read up on energy conservation and what it
means?

You should read the links a bit more or look for different links than
you have now..
It has nothing to do with "two" different points.
It is beginning and end that are the two "points" to compare
to prove the "conservation of the system".

No. A conservation law applies at all times, not just
chosen instants.

Hmm?
Seems you are ignoring the "total" system.

Here's another. Two Toyotas traveling at the speed limit hit each
other in a head-on collision. Broken glass, bent metal, blown
airbags ensue. But just five seconds after the collision, there
seems to be much less kinetic energy than there was just six
seconds ago. Where did it go?

It was turned into heat

Yes.

and spread out parts

That are now stationary, and so their energy is not kinetic.

It is simply back to the zero kinetic energy all over again.

If it's "back to" then it wasn't constant.

The "battery" has gone dead.
The charge is gone.
The energy put in "equaled" the energy take out.
Seems it works fine for conservation.

The total of all energy types involved is constant, but
the electric potential energy is not. Nor are any of
the other energy types constant taken individually.

It works just like a battery would that "stores" energy.

If you mean kinetic and potential energies taken together
then, yes, the analogy is apt.


and gravity soaked
it all up.
That gravity is magical.
How is it able to have so much energy and still not increase
or decrease in energy?

There *is* energy in the gravitational field. Just not *kinetic*
energy. There is *gravitational potential* energy, which is not
kinetic energy. The total amount of energy is conserved, but that
energy comes in many forms other than kinetic and is converted from
one form to another. Kinetic energy, however, is not conserved
because some of the kinetic energy gets turned into other forms and
is no longer kinetic.

That is just silly PD,
regular energy can be transformed to all sorts of energy, mechanical,
heat, light, and even kinetic energy.
So why do you not allow kinetic energy to do the same?

It does do the same. That's what PD is saying. In the
limited example of objects in a gravitational field without
other types of interaction, the exchange is between kinetic
and gravitational potential energy.

Why do you "not find the totals that do start at 0 and end
at 0.
Kinetic energy is just the other side of the "energy" coin.

"Energy" embraces many forms, kinetic being only one. All
are interconvertible in one way or another. The grand total
of all types is constant, but the individual types taken
separately are not.



It must be the magic of "spacetime".
LOL

Here's another. You light a firecracker on the desk. Twenty
milliseconds before the detonation, there's a teeny bit of kinetic
energy in the lit fuse. Twenty milliseconds after the detonation,
there's a whole bunch more kinetic energy in the flying shards. Now
where did all that kinetic energy come from? Was it hiding before?
Was it stored in a black hole just under the desk?

Silly PD,
the kinetic energy was stored in the gun powder.

Absolutely! Just not as kinetic energy. As chemical potential energy,
yes, but not kinetic energy. The *kinetic* energy is not conserved,
but the *total* energy, counting the sum of all forms of energy in
the firecracker, is conserved.

And again,
You simply give it different names and then say it is not kinetic.

Well, yes, because it is not. A pretty good reason, no?

That is again the same thing. You are a kinetic energy bigot.
It is ok for you to say energy from the battery turns the motor
and becomes kinetic energy when the car is moving but
it is not ok to lose that kinetic energy just like you would lose
"energy" itself.

I have no idea what that is supposed to mean. Of course
kinetic energy can be lost -- it can be converted to other
forms of energy.

That is not right PD.
It is taking away kinetic energy's natural rights to change
into other forms and then lose all the energy it was given
in the end.
Again 0 at start and 0 at end.
No violation in a conservation of kinetic energy..

James really, really doesn't understand what a conservation
law is. Something that is conserved has the same value
at all times. Sometimes that means taking more than one
thing at a time so that their total is what is conserved,
like the sum of potential and kinetic energy in a
gravitational field.


It was just "stable and balanced" until you broke it's perfect spin
and balance.
:)

Now, in considering these, are you still SURE that kinetic energy
is conserved? Do you need to look up what conservation of energy
means? Would you like a handy link you can click on and read?

Would you like to say gravity is also not conserved then?
Gravity must be kinetic energy right since it can move things
and smash things and make the kinetic energy just
"dissapear".

Uh, no. It is a *different* form of energy. Kinetic energy is very
specific.

What a bunch of crap.
It seems you allow kinetic energy be turned into energy but
won't let the opposite occur.

PD's given you examples where interconversion in both ways
occurs. So what are you on about?

That is sad PD.
You have kicked kinetic energy out of the energy family
and told it that it is no longer part of the family.

No, he said that it is part of a family and works and
plays well with the others.

You are a mean jerk and should be kicked out of science
for doing that to the energy family..

You're acting out gain, James. Time for you to go
sit in a corner for awhile.

.

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