What's wrong with Pete M. Brown solution?
Dono
No wonder you were so cagey in sharing it, there are quite a few
glaring
mistakes. I hope that you will take the following as constructive
criticism and that you'll correct your page. Here it goes:
1.It is quite clear that you can't solve the problem by using
relativistic mass, the "m" in your equations is rest mass. The reason
is quite simple, starting from eq.1 you should be writing:
d(\gamma*m*v)/dt=q(E+vxB)
2. You keep avoiding writing the ODE above, instead you go through all
kinds of girations and you arrive to...
3. ....the following commedy of errors (I copy and posted exactly from
your solution)
"From the diagram it is easy to see that a positive charge q moves in
a clockwise motion around the circle. w is known as the cyclotron
frequency. To find an explicit expression for w we start with the
expression for the magnitude of the Lorentz force which is F = qvB.
Since the motion is transverse to the acceleration we also have F = ma
= mRw2 = qvB = qRwB or w = mv/qB = p/qB. "
4. You are now mixing relativity with Newtonian mechanics (F=ma),
exactly like Juanshito . This is a "no-no".
You simply cannot have any "F=ma" in a relativistic page, if you want
to be taken seriously.
5. This is the first time that mass, "m" appears in your solution (it
should have appeared from the very beginning, in eq.1) but you were
too focused on avoiding it. If you had it early on, in the ODE
d(\gamma*m*v)/dt=q(E+vxB), you would have avoided this embarassing
error.
6. Now, as a result of the error at point 4, you have a completely
wrong formula for the "cyclotron frequency". Contrary to what you
derived, w is NOT equal to mv/qB = p/qB.
Nowhere close.
7. Now, you have spent quite a lot of effort writing a lot of formulas
but you are missing the most basic thing (aside from botching the
formula for w). The particle moves in a circle, so what is the value
for its radius? You come close to calculating the radius from eq.13
but not quite.
Pete,
You are not a bad guy but you have a bee under your bonnet when it
comes to relativistic mass. If you were doing the computations
honestly you would have arrived to the correct results. In order to do
that , you need to use rest mass, ok? I know that this pains you but
this is the truth.
Now, I will also transfer to Dave the solution for the case when you
have BOTH a non-null B AND a non-null E. Don't even dream of trying to
solve this problem by using relativistic mass, you can't. On the other
hand, if you start with d(\gamma*m*v)/dt=q(E+vxB) and you pay
attention to the math, you might get the correct result. This is a
tougher problem, so I suggest that you get cracking. Oh, and you will
need to use the rest mass m, ok :-)
Eric Gisse
[...]
> Now, I will also transfer to Dave the solution for the case when you
> have BOTH a non-null B AND a non-null E. Don't even dream of trying to
> solve this problem by using relativistic mass, you can't. On the other
> hand, if you start with d(\gamma*m*v)/dt=q(E+vxB) and you pay
> attention to the math, you might get the correct result. This is a
> tougher problem, so I suggest that you get cracking. Oh, and you will
> need to use the rest mass m, ok :-)
Could you summarize why pete cares so much about relativistic mass?
Dirk Van de moortel
b3cccaf6-7e23-457a...@a9g2000prl.googlegroups.com
He can't stand Tom Roberts.
That's all there is to it.
Dirk Vdm
Dono
It is just a bee under his bonnet, like I said.
Now, this gave me the opportunity to give some practical examples
where relativistic mass is rendered useless in solving practical
problems.
Dono
SperM.hotmail.com> wrote:
> Eric Gisse <jowr...@gmail.com> wrote in message
>
> b3cccaf6-7e23-457a-bf95-c1ea25975...@a9g2000prl.googlegroups.com
...but this puts him in an embarassing position (see the errors in his
webpage).
dlzc
You mean a trusty, hoary "claw hammer" can be used as a kitchen
utensil from time to time, but is really not suited to picking your
teeth after the meal?
What a *huge* surprise.
Relativistic mass is a tool, like many others. It has its proponents,
and its detractors. It can be used in some applications, and not in
others. It only moves some complexity from the formulae to an
intermediate result, a result that can be applied in some situations,
but not others.
OK, so how does a web page that addresses (apparently) only
relativistic mass answer the question on the web page? *Which* mass
varies with speed, is not the question it purports to answer, nor by
how much, nor is it to slam one "camp" or another.
Does rest mass vary with speed? No.
Does inertial mass vary with speed? Yes and No.
Does gravitational mass vary with speed? Yes.
Seems like only the latter two needed fleshing out... what was so bad
about the old version, other than wasting verbiage in slamming a tool?
David A. Smith
Dono
The point is that rest mass can be always used.
I gave Pete a few examples where relativistic mass is unusable. In
order to drive the point I picked one case right from his incorrect
cyclotron solution. Unfortunately old Pete elected to pull the horse
blinders all the way over his eys :-)
Pmb
"dlzc" <dl...@cox.net> wrote in message
news:ab33df3a-915a-4a8c...@f1g2000prb.googlegroups.com...
Dear Dono:
On Jun 25, 7:19 am, Dono <sa...@comcast.net> wrote:
> On Jun 25, 7:16 am, Eric Gisse <jowr...@gmail.com> wrote:
>
> > On Jun 25, 5:58 am, Dono <sa...@comcast.net> wrote:
>
> > [...]
>
> > > Now, I will also transfer to Dave the solution
> > > for the case when you have BOTH a non-null B
> > > AND a non-null E. Don't even dream of trying to
> > > solve this problem by using relativistic mass,
> > > you can't. On the other hand, if you start with
> > > d(\gamma*m*v)/dt=q(E+vxB) and you pay attention
> > > to the math, you might get the correct result.
> > > This is a tougher problem, so I suggest that
> > > you get cracking. Oh, and you will need to use
> > > the rest mass m, ok :-)
I see that Dono finally found that page. From this response its clear he was
unable to understand the derivation. I suspected as such.
> > Could you summarize why pete cares so much about
> > relativistic mass?
I'm waiting for Dono to answer the questions I asked.
Pete
Dono
>
> I see that Dono finally found that page. From this response its clear he was
> unable to understand the derivation. I suspected as such.
>
Pete,
sadly you are not only bad at physics but utterly dishonest as well.
Your solution is riddled with mistakes.
I had a look at your solution : http://www.geocities.com/physics_world/sr/cyclotron.htm
No wonder you were so cagey in sharing it, there are quite a few
mistakes. I hope that you will take the following as constructive
criticism and that you'll correct the page. Here it goes:
1.It is quite clear that you can't solve the problem by using
relativistic mass, the "m" in your equations is rest mass. The reason
is quite simple, starting from eq.1 you should be writing:
d(\gamma*m*v)/dt=q(E+vxB)
2. You keep avoiding writing the ODE above, instead you go through all
kinds of girations and you arrive to...
3. ....the following commedy of errors:
"From the diagram it is easy to see that a positive charge q moves in
a clockwise motion around the circle. w is known as the cyclotron
frequency. To find an explicit expression for w we start with the
expression for the magnitude of the Lorentz force which is F = qvB.
Since the motion is transverse to the acceleration we also have F = ma
= mRw2 = qvB = qRwB or w = mv/qB = p/qB. "
4. You are now mixing relativity with Newtonian mechanics (F=ma),
exactly like Juanshito did earlier in this thread. This is a "no-no".
You simply cannot have any "F=ma" in a relativistic page, if you want
to be taken seriously.
5. This is the first time that mass, "m" appears in your solution (it
should have appeared from the very beginning, in eq.1) but you were
too focused on avoiding it. If you had it early on, in the ODE
d(\gamma*m*v)/dt=q(E+vxB), you would have avoided this embarassing
error.
6. Now, as a result of the error at point 4, you have a completely
wrong formula for the "cyclotron frequency". Contrary to what you
derived, w is NOT equal to mv/qB = p/qB.
Nowhere close.
7. Now, you have spent quite a lot of effort writing a lot of formulas
but you are missing the most basic thing (aside from botching the
formula for w). The particle moves in a circle, so what is the value
for its radius? You come close to calculating the radius from eq.13
but not quite.
Pete,
You are not a bad guy but you have a bee under your bonnet when it
comes to relativistic mass. If you were doing the computations
honestly you would have arrived to the correct results. In order to do
that , you need to use rest mass, ok? I know that this pains you but
this is the truth.
Now, I will also transfer to Dave the solution for the case when you
Peter M. Brown
"Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
in message news:Ets8k.80331$312....@newsfe12.ams2...
That's a very silly response and totally irrelevant to my views on
relativistic mass.
Eric Gisse
SperM.hotmail.com> wrote:
> Eric Gisse <jowr...@gmail.com> wrote in message
>
> b3cccaf6-7e23-457a-bf95-c1ea25975...@a9g2000prl.googlegroups.com
>
>
> > [...]
>
> >> Now, I will also transfer to Dave the solution for the case when you
> >> have BOTH a non-null B AND a non-null E. Don't even dream of trying to
> >> solve this problem by using relativistic mass, you can't. On the other
> >> hand, if you start with d(\gamma*m*v)/dt=q(E+vxB) and you pay
> >> attention to the math, you might get the correct result. This is a
> >> tougher problem, so I suggest that you get cracking. Oh, and you will
> >> need to use the rest mass m, ok :-)
>
> > Could you summarize why pete cares so much about relativistic mass?
>
> He can't stand Tom Roberts.
> That's all there is to it.
>
> Dirk Vdm
That's a roundaboue way of going about things. Is the direct approach
not his style?
Dirk Van de moortel
yt-dnZXln-gciv7V...@comcast.com
You just killfilled me:
http://groups.google.com/group/sci.physics.relativity/msg/b17044da26f3fb94
Replying to someone whom you killfiled is a bit silly.
Dirk Vdm
Dirk Van de moortel
Talking of 'direct approach' :-)
He also killfiled Tom.
Dirk Vdm
Pmb
I had to reset my system which deleted my killfile. I have to start a new
one.
Thank you for reminding me that you were in it.
Pete
Androcles
[snip crap]
Got past my kill file again, cretin?
Oh well, any variation to add.
*plonk*
Dirk Van de moortel
M9Gdndd4oocN9_7V...@comcast.com
I don't believe that.
Dirk Vdm
Dono
>
> That's a very silly response and totally irrelevant to my views on
> relativistic mass.
Pete,
Look at your page:
http://www.geocities.com/physics_world/sr/cyclotron.htm
The errors are embarassing:
1. You mix SR with Newtonian mechanics (F=ma!)
2. You messed up the computations of BOTH the cyclotron frequency (w)
AND the particle radius (r)