Subject: Re: HELP!! STUCK! (Phys HW) -calling all geniusses-
From: mjrust@erols.com (Mike Rust)
Date: Mon, 16 Dec 96 05:41:31 GMT
In article , MILWARD wrote:
>
>There are a couple of questions that I have been set as physics homework, and I
>just cannot work them out, and I would be really grateful if YOU know the
>answers to either of them:
Oh, fine. I'd rather do this than my government assignment.
>
>Q: Derive an expression for the kinetic energy of a particle of mass 'm' which
>has momentum 'p'.
O.K. Take the typically used expression for kinetic energy: KE=(1/2)mv^2
which I will conveniently re-write as: KE=(1/2)(mv)*v. I will now pluck the
multiplying both sides of an equation by the same quantity trick out of my
pocket so: m*KE=(1/2)(mv)*(mv)
But, as we all know, the linear momentum of a particle is defined as: p=mv
So, m*KE=(1/2)p^2, and KE=(p^2)/(2*m)...
>
>Q: Two tolleys, p & q, of masses 0.50kg and 0.30kg resp. are held together on a
>horizontal track against a spring which is in a state of compression. When the
>spring is released the trolleys separate freely and p moves to the left with an
>initial velocity of of 6ms-1. Calculate:
I'm going to assume this problem is talking about a spring between two
trolleys p and q (perhaps we should give these trolleys the names linear
momentum and electric charge respectively? Tee-hee.)
Ignore me.
>a) The init. velocity of q.
Linear momentum is conserved since friction is non-existent or can be
neglected during the expansion of the spring and all other external forces
balance. The initial linear momentum is zero since everything starts from
rest. The linear momentum after the spring expands must also by zero by our
clever little conservation law:
p(trolley-p) + p(trolley-q) = 0
m(trolley-p)v(trolley-p) + m(trolley-q)v(trolley-q) = 0
But we know the masses of both trolleys and the velocity of trolley p.
Choosing left as positive:
v(trolley-q) = -m(trolley-p)v(trolley-p)/m(trolley-q) = -10(m/s)
>b) the totsl kinetic energy of the system.
Well, the total kinetic energy of the system changes with time as the spring
expands since energy stored in the internal structure of the spring is
converted into kinetic energy of the trolleys. The total mechanical energy
(kinetic + interaction energy in spring) of the system does stay constant, and
also happens to be equal to the total kinetic energy of the system after the
spring has fully expanded. This is fairly easy to calculate:
E = KE(trolley-p) + KE(trolley-v) + U(spring)
E = (1/2)m(trolley-p)[v(trolley-p)]^2 + (1/2)m(trolley-p)[v(trolley-v)]^2 + 0
E = 24 J
>Calculate also the initial velocity of q if trolley p is held still when the
>spring, under the same compression as before, is released.
This case is identical to having the spring mounted to a wall rather than
to trolley p. If the spring is under the same compression then it must be
storing the same amount of mechanical energy found in part B (24 J). In this,
case however, all of the energy stored in the spring must be transferred into
trolley p. Conservation of energy can be used to solve the problem:
U(spring) = KE(trolley-q)
24 J = (1/2)m(trolley-q)[v(trolley-q)]^2
A touch of algebra shows that:
v(trolley-q) = sqrt((48 J)/m(trolley-q)) = 12.649 (m/s)
>
>
>-GO ON! PROVE YOUR GENIUS TO ALL!!-
Huh?
>
>
>
Love,
Mike Rust
mjrust@erols.com
mrust@tjhsst.edu
Subject: time and mass and heat correlation
From: "Alexander V. Frolov"
Date: 16 Dec 1996 08:59:52 +0300
Perhaps I have not well knowledge of English and my statements are sound
in some different from real russian sense of it. Pavel Ouspensky wrote
about heat and time correlation. Please, look Ch.10 New model of Universe,
page 402 in russian edition. Then, p.408 "physicists did not understood
that electron belong to other world"; page 418 "Sir Oliver Lodg consider the
density of ether in billion times higher than density of the water... and mater
is only empty space, bubbles in a mass of the ether"; after this place author
described theory of Einstein; then Ouspensky reproduce text of E.S.Edington
about sense of energy and curvature of space; then p.439 about 6-dimensional
space-time; p.451 about velocity as a property of space, velocity have a
sense of a angle; p.453 "molecules are 6-dimensional: 3 spatial and 3 temporal
dimensions; p.454 by Ouspensky dimensions are depend of the sizes of object.
In this point I must add that it is property of a space that have certain
curvature. If the same object is placed in space that have other curvature
the properties of the object are changed; p.459 about motion and matter;
p.462 "electrons are particles of time but not a particles of a space", electrons
have more time inside of themself than they have a space inside if themself.
On the base of above I made conclusions about time-motion-heat correlation.
Also I hope that you saw the book of japan physicist R.Utiama "The theory of
Relativity", p.92-93 in russian edition, F. 16.2' - F.16.5 he expalne that
mass of the body is increasing if there is heat input into the body. If you
can connect mass and time notions, you'll make conclusion about time and heat
correlation.
Also there are many russian papers on the same.
I am not a proffy. All researches are made by my own plan.
You can take the book we published as Proceedings of the conference. Cost
is USD 60. Way for payment is Western Union transfer on my name, in St.-Petersburg
or bank transfer in my account:
Incombank, Moscow, St.Petersburg Branch, Branch N 200089082,
SWIFT: INCORUMMSPB, Russia, account N 671070463,
Mr. Alexander V. Frolov
Best regards,
Alexander V. Frolov
---
Alexander V. Frolov, P.O.Box 37, St.-Petersburg, 193024 Russia
Tel:7-812-2747877
Subject: Re: Time and its existance
From: savainl@pacificnet.net (Louis Savain)
Date: Mon, 16 Dec 1996 07:22:24 GMT
In article <592e1o$1e6@usenet.rpi.edu>, nospaam@pascal.stu.rpi.edu
(Peter F. Curran) wrote:
>In article <32b5b39e.3988264@netnews.worldnet.att.net>,
> alien.spydr@worldnet.att.net (a. s.) writes:
>>On 14 Dec 1996 22:54:55 GMT, curran@remove_this.rpi.edu (Peter F.
>>Curran) wrote:
>>
>>->In article <58v7us$hht@trojan.neta.com>,
>>-> blair@trojan.neta.com (Blair P Houghton) writes:
>>->>Peter F. Curran wrote:
>>
>>
>>->>> Time exists independently of us, and our minds
>>->>>were never intended to be accurate chronological measuring
>>->>>devices.
>>
>> Someone give me their best explaination as to "how"
>> time exists... As I've suppositionally offered before,
>> my position for the sake of philosophical discussion is that
>> time does not exist in any form beyond that of an
>> intellectual concept. It has no pysical existance, therefore,
>> it can't be accessed for travel.
>[...]
>BTW, time travel IS possible, but only
>into the future, and only at tremendous
>expense. Go fast enough, and in the time
>you age a minute, the world will have aged
>100yrs. It is only travel into the past
>that upsets causality and denies free
>will.
Sorry Peter, time travel (future or past, it doesn't matter) is the
biggest deception being inflicted upon an unsuspecting public by a
number of physicists who either don't know what they're talking about
or read too much sci-fi. As physicists, they should know better. The
idea that something can move in time is illogical because it is
circular. In fact, as every physicist should know, nothing moves in
spacetime. Spacetime is the deadest thing since dinosaurs. Luckily
for the logically minded, a few physicists are aware of it. Here's a
quote from the brilliant physicist and philosopher Joe Rosen of the
University of Central Arkansas:
"[...] Thus there is an objective past-future differentiation. It is
not merely a matter of definition or of entropy considerations in
regard to information storage systems (physical memories). What has
been has indeed objectively been and is no more. What will be,
objectively is not and has not been (and, in fact, is not even fully
determined, according to quantum indeterminacy and even to classical
indeterminacy). All physical systems ride the universal wave of
becoming. Any awareness (ours or that of other intelligence) of past
and future reflects the objective wave of becoming. There is no
problem of "the arrow of time." There simply is no arrow of time, as
if time could go one way rather than another. That metaphor is an
unfortunate result of spatializing time. The picture of time as a
line along which one might travel in one direction or the other is a
conceptual disaster. Time is becoming. Becoming is change. The
undoing of a change is also a change, thus also becoming. There is no
"unbecoming.""
-Joe Rosen, 1993. "TIME, C, AND NONLOCALITY: A GLIMPSE BENEATH THE
SURFACE?
As hard as it may be, we'll all have to face the hard fact of reality:
There is no time dimension. The past is irretrievably lost (unless
someone records it, which BTW, as strange as it seems, maybe exactly
what is happening to our corner of the universe) and the future has
not yet arrived. Only the NOW exists.
Best regards,
Louis Savain
"O judgment! thou art fled to brutish beasts,
And men have lost their reason." W.S.
Subject: Re: A case against nuclear energy?
From: redin@lysator.liu.se (Magnus Redin)
Date: 16 Dec 1996 07:38:23 GMT
hatunen@netcom.com (DaveHatunen) writes:
>In article <592767$cka$1@newsy.ifm.liu.se>,
>Magnus Redin wrote:
>> I have no idea on how it is in USA and I dont care much except that
>> your CO2 releases affect the whole planet and your popular culture
>> is dominating the western culture so if "Hollywood" thinks there is
>> a (US) problem lots of Swedes also think there is a Swedish
>> problem. :-(
> Isn't a bit unfair to throw in our popular culture here? Definitely
> not germane to the discussion. And note, too, that there are no
> Americans forcing Swedish hands into Swedish pockets and forcing
> Swedish kroner into the eager hands of the purveyors of our popular
> culture, many of whom are undoubtedly eager Swedish middlemen. It is
> simply the marketplace in operation.
*shrug* It seems to simply work that way, I dont propose that anything
more should be done about it then some nuclear PR work and perhaps
even some of it needs to me aimed at USA? But I am not an expert that
can tell if that is a good idea or not. As you say, people are free to
choose and that is a good thing. And I dont realy care who earns the
money, I get irritated on irrelevancies, half truths and lies
regardless of the source.
> Um. Historically the Swedes have been quite good at heavy empire
> building. After all, "Russia" is a Swedish word.
Ok, that were some time ago. :-)
Regards,
--
--
Magnus Redin Lysator Academic Computer Society redin@lysator.liu.se
Mail: Magnus Redin, Björnkärrsgatan 11 B 20, 584 36 LINKöPING, SWEDEN
Phone: Sweden (0)13 260046 (answering machine) and (0)13 214600
Subject: Re: Acceleration?
From: kfischer@iglou.com (Ken Fischer)
Date: Mon, 16 Dec 1996 08:39:22 GMT
J. Matthew Nyman (timeflux@concentric.net) wrote:
: I have a quick question.
: Let's say I fall over a bannister and down to the first floor of a
: house. During my fall, technically, I am in free fall, right?
Certainly, except for air resistance.
: In other words, I don't approach the ground - the ground
: approaches me due to the motion of the Earth.
Have you been reading about the Divergent Matter GUT. :-)
Classical physicists would say you are ready for the guys
in the white jackets, while Relativists would say you have
discovered Einstein's Principle of Equivalence, but maybe
it would be better not to carry it too far, after all, a
guy in New Zealand says the same thing, and the Earth
can't be moving both ways at once.
But I think you have it right.
: So gravity really does not kill me, because when I
: am in the air, gravity isn't touching me.
No, gravity won't hurt you, hitting something
when you are moving too fast will.
: But the Earth is hurtling in my direction carrying the
: first floor with it, and that is what kills me.
No, the center of mass of the Earth does not move
just because you fall, your center of mass doesn't move
because you are in freefall.
It is the surface of the Earth that is accelerating
outward radially away from the Earth's center of mass.
***** !!!! W A R N I N G !!!! ******
If you are in school, when you take a test, use the
answer you find in the textbook, I am not responsible for
failing grades!
: But if I am in free fall, then that means I am not accelerating.
That is what General Relativity says, the inertial
coordinates are falling, and you are in inertial motion
(not accelerating), and the coordinate system is either
falling or the Earth's surface is accelerating upward,
but don't expect anyone with a college degree to say
that the Earth is getting bigger, it would hurt their
chance of earning a living (they don't really believe
it anyway). :-)
: So why is it that objects that fall, do accelerate at 16
: feet per second per second?
They don't, they fall at 32 feet per second/per second,
but at the end of the first second, they are moving at 32 feet
per second relative to the point that they fell from, but
they fall 16 feet the first second, becaust that is the
average speed for one second of fall at 32 feet per second/
per second acceleration.
Oddly, an object falls 1 foot in the first one-quarter
second, 3 feet in the second quarter second, 5 feet in the
third quarter second, and 7 feet in the fourth quarter second.
I should have said "about" before each number, because
it isn't exact, but I feel that either Newton or Galileo
established the length of the "foot" because of the distance
something falls in one-quarter second, and the only reason
the numbers are not correct is that they couldn't correct
for air resistance properly, and/or the standard for the
"foot" wasn't kept very well before modern times.
: I hope this makes sense. I think I'm missing something very
: simple, but fundamental here.
No, you have just re-invented Einstein's Principle
of Equivalence, gravity and acceleration are so identical
that they must be the same thing.
But it is not a good idea to let this knowledge
affect your life, and it will if you argue it too strongly,
and it could get anyone a failing grade.
Check my homepage an about a month or so, I hope
to have some math to explain why there is confusion about
what accelerates. The homepage now contains information
about the concept of Divergent Matter (expanding matter),
but it is just descriptive now.
Kenneth Edmund Fischer - Inventor of Stealth Shapes - U.S. Pat. 5,488,372
Divergent Matter GUT of Gravitation http://www.iglou.com/members/kfischer
Subject: Power output comparison
From: fc3a501@AMRISC04.math.uni-hamburg.de (Hauke Reddmann)
Date: 16 Dec 1996 11:41:00 GMT
A Saturn V rocket has a big power output, but a
big mass too. When you compare a human, a horse,
a car, a plane, ..., is P/m roughly constant?
Or maybe a power :-) law P^a/m^b=c should apply?
Anyone with some actual data?
--
Hauke Reddmann <:-EX8
fc3a501@math.uni-hamburg.de PRIVATE EMAIL
fc3a501@rzaixsrv1.rrz.uni-hamburg.de BACKUP
reddmann@chemie.uni-hamburg.de SCIENCE ONLY
Subject: Re: A Question about Piezoelectricity
From: kgloum@news.HiWAAY.net (Kelly G. Loum)
Date: 16 Dec 1996 11:34:36 GMT
Laurent LE GUILLOU (llg@lola.univ-lemans.fr) wrote:
: Is there a physicist who can help me ?
: I want to show the phenomenon of piezoelectricity : the
: direct piezo effect and the reverse effect.
: - For the direct effect, how can i do ?
: what sort of device can i use to show this effect ?
: i don't know how to apply a big and controlled stress
: on a piezo crystal, and how to measure the polarisation of
: crystal...
: - For the reverse effect, how can i measure the deformations
: of crystal when i apply an electric field ? this deformation
: seems to be very little (about ten micrometers, i think). i've
: thought to use optical ways (interferometry) to measure it. but
: it demands big devices...
: If anyone can help me to prepare my experiments... Thanks
: Laurent LE GUILLOU
: Etudiant en Licence de Physique
: Universite du Maine, France
: llg@lola.univ-lemans.fr
There are hand-held cigarette lighters that you can get at most drug and
department stores that use an inch-long piezoelectric crystal to produce
an arc to light the flame. The one I saw was designed to be used to light
your gas water heater, etc. The crystal itself is about about an inch
long. There is a weight on one end of the crystal and a hammer taps the
other. They produce a very low current (thin blue arc) of, I'd guess,
about 15000 volts.
They are only a couple dollars each.
I'll bet you could buy two of them and use the pulse from one to distort
the other. You could put a diaghram on the end of the other and I'll bet
you'd hear a click.
Kelly Loum
Subject: Re: Time and its existance
From: B Jones
Date: 16 Dec 1996 12:07:35 GMT
nospaam@pascal.stu.rpi.edu (Peter F. Curran) writes:
> In article <32b5b39e.3988264@netnews.worldnet.att.net>,
> alien.spydr@worldnet.att.net (a. s.) writes:
> >On 14 Dec 1996 22:54:55 GMT, curran@remove_this.rpi.edu (Peter F.
> >Curran) wrote:
> >
> >->In article <58v7us$hht@trojan.neta.com>,
> >-> blair@trojan.neta.com (Blair P Houghton) writes:
> >->>Peter F. Curran wrote:
> >
> >
> >->>> Time exists independently of us, and our minds
> >->>>were never intended to be accurate chronological measuring
> >->>>devices.
> >
> > Someone give me their best explaination as to "how"
> > time exists... As I've suppositionally offered before,
> > my position for the sake of philosophical discussion is that
> > time does not exist in any form beyond that of an
> > intellectual concept. It has no pysical existance, therefore,
> > it can't be accessed for travel.
> >
> > a. s.
> >______________________________________________
> > an itsy bitsy spydr
> > from somewhere in deep space.
> >an itsy bitsy spydr from
> > somewhere in deep space.
>
>
> Interesting notion that it does not
> exist at all... I agree that it is
> not like any other physical object or
> effect, however this doesn't necessarily
> mean that it is not real. It does lend
> itself to testing as in relativity, and
> the universe would certainly be a
> different place without it. Perhaps it
> can be defined as "that which separates
> matter in one state from another". I
> don't really have a good definition at
> the moment! :)
>
> BTW, time travel IS possible, but only
> into the future, and only at tremendous
> expense. Go fast enough, and in the time
> you age a minute, the world will have aged
> 100yrs. It is only travel into the past
> that upsets causality and denies free
> will.
>
> - Pete
>
> --
> donut male: nospaam@pascal.stu.rpi.edu
> Use address in Organization line, finger
> for PGP key. Antispaam test in progress.
>
Subject: Re: Time and its existance
From: nospaam@pascal.stu.rpi.edu (Peter F. Curran)
Date: 16 Dec 1996 08:42:11 GMT
In article <32b6f53a.11135050@pubnews.demon.co.uk>,
savainl@pacificnet.net (Louis Savain) writes:
>In article <592e1o$1e6@usenet.rpi.edu>, nospaam@pascal.stu.rpi.edu
>(Peter F. Curran) wrote:
>
>>In article <32b5b39e.3988264@netnews.worldnet.att.net>,
>> alien.spydr@worldnet.att.net (a. s.) writes:
>>>On 14 Dec 1996 22:54:55 GMT, curran@remove_this.rpi.edu (Peter F.
>>>Curran) wrote:
>>>
>>>->In article <58v7us$hht@trojan.neta.com>,
>>>-> blair@trojan.neta.com (Blair P Houghton) writes:
>>>->>Peter F. Curran wrote:
>>>
>>>
>>>->>> Time exists independently of us, and our minds
>>>->>>were never intended to be accurate chronological measuring
>>>->>>devices.
>>>
>>> Someone give me their best explaination as to "how"
>>> time exists... As I've suppositionally offered before,
>>> my position for the sake of philosophical discussion is that
>>> time does not exist in any form beyond that of an
>>> intellectual concept. It has no pysical existance, therefore,
>>> it can't be accessed for travel.
>>[...]
>>BTW, time travel IS possible, but only
>>into the future, and only at tremendous
>>expense. Go fast enough, and in the time
>>you age a minute, the world will have aged
>>100yrs. It is only travel into the past
>>that upsets causality and denies free
>>will.
>
> Sorry Peter, time travel (future or past, it doesn't matter) is the
>biggest deception being inflicted upon an unsuspecting public by a
>number of physicists who either don't know what they're talking about
>or read too much sci-fi. As physicists, they should know better. The
>idea that something can move in time is illogical because it is
>circular. In fact, as every physicist should know, nothing moves in
Whoa! I think your conclusion that time is circular is far
from proven and is probably in conflict with the majority
of cosmologists. Experiments have been conducted which
demonstrate the time dialation predicted by special and
general relativity. As things go faster, time goes slower
for them.
>spacetime. Spacetime is the deadest thing since dinosaurs. Luckily
>for the logically minded, a few physicists are aware of it. Here's a
O.K, so your view is supported by a few physicists, while mine
is supported by the majority.
>quote from the brilliant physicist and philosopher Joe Rosen of the
>University of Central Arkansas:
>
>"[...] Thus there is an objective past-future differentiation. It is
>not merely a matter of definition or of entropy considerations in
>regard to information storage systems (physical memories). What has
>been has indeed objectively been and is no more. What will be,
>objectively is not and has not been (and, in fact, is not even fully
>determined, according to quantum indeterminacy and even to classical
>indeterminacy). All physical systems ride the universal wave of
>becoming. Any awareness (ours or that of other intelligence) of past
>and future reflects the objective wave of becoming. There is no
>problem of "the arrow of time." There simply is no arrow of time, as
>if time could go one way rather than another. That metaphor is an
>unfortunate result of spatializing time. The picture of time as a
>line along which one might travel in one direction or the other is a
>conceptual disaster. Time is becoming. Becoming is change. The
>undoing of a change is also a change, thus also becoming. There is no
>"unbecoming.""
>
>-Joe Rosen, 1993. "TIME, C, AND NONLOCALITY: A GLIMPSE BENEATH THE
>SURFACE?
>
>As hard as it may be, we'll all have to face the hard fact of reality:
>There is no time dimension. The past is irretrievably lost (unless
>someone records it, which BTW, as strange as it seems, maybe exactly
>what is happening to our corner of the universe) and the future has
>not yet arrived. Only the NOW exists.
>
As I said, I agree travel into the past is impossible, however
travel into the future, (depending on your definition of
traveling), most assuredly is. The relativistic time dialation
effect doesn't conflict with the statements above since in the
at rest time frame, events proceed normally. However, for the
traveler in the high velocity spaceship, events are happening
too, but just at a lower rate, (which he sees as normal). When
the traveler returns to our inertial reference frame he hasn't
upset anything. This has been demonstrated to actually occur
with high accuracy clocks.
Likewise, freezing someone and then unthawing them 1000 years
later may eventually prove to be technologically feasible and
could be called time travel.
- Pete
--
dough knot male: nospaam@pascal.stu.rpi.edu
Use address in Organization line, finger
for PGP key. Antispaam test in progress.
Subject: Monopole non-conservation should simplify vacuum physics.
From: mburns@goodnet.com (Michael J. Burns)
Date: 16 Dec 1996 13:15:18 GMT
Magnetic monopoles cannot conserve angular momentum or energy. "Proofs"
to the contrary only cover special cases - which, in the absence of a
defined potential, cannot show the general case. With a proof not
available, a search for examples of non-conservation should have been
ethically impelled. Such a search easily yields the suspected counter-
examples to conservation.
In view of the non-conservation of a postulated monopole, it is easy to
imagine the all-but-instantaneous repair of the defect emerging from the
vacuum - it would be free. Each monopole pair would be transformed to a
dipole field. So, cannot a treatment of vacuum physics based on potential
fields afford to ignore monopoles, which are inconsistent with potentials
from the first?
--
Michael J. Burns http://www.indirect.com/www/mburns/
"We are such stuff "Oh brave new world,
As dreams are made on, and our little life That has such people in't!"
Is rounded with a sleep."
Subject: Re: determinism vs non-determinism, was: Really random? (now back on original topic)
From:
Date: Mon, 16 Dec 1996 08:17:48 EST
Not to hopelessly confuse things, but is anyone familiar with Greg Chaitin's
recent work? The gist of it is that, given a finite set of axioms, one can
only prove a finite number of theories. If you bring Goedel into the picture,
the result is that maybe we shouldn't be wielding Occam's razor quite so
religiously. The razor is a great tool, no question about that, but it begins
to look as though we aren't going to be able to extend scientific theory
forever, without eventually just accepting some unprovable truths as new
postulates. For now though, there seem to be plenty of provable truths left. :)
i'm only posting this into this thread because there seemed to be some
discussion of the magic observer principle. it was suggested that any
theory about an observer that cannot affect the universe wasn't scientific.
i would argue that such theories may be unprovable with our current set of
axioms, but this doesn't necessarily make them unscientific; just relatively
uninteresting or un-useful. However, in the event that a theory of the
unobserved observer produced some testable predictions that could be borne
out by experiment, such theory would suddenly be quite the opposite. Some
recent work published in Sci.American described how it may be possible to
measure certain bits of the quantum state of a particle without actually
interacting with said particle, a notion which formerly was thought to be
impossible. Ie- the future may or may not be deterministic, but it will
certainly be interesting.
-j.allen
Emergent Systems Group
Dept. of Computer Science
University of Maine
http://www.umcs.maine.edu/~obelix
Subject: Re: Ultraviolet Light Source wanted
From: ch1grh@sunc.sheffield.ac.uk (G Harris)
Date: 16 Dec 1996 14:15:49 GMT
Roger Miller (rmiller@landau.ucdavis.edu) wrote:
: Ja det er MEG! (renato.bugge@fysel.unit.no) wrote:
: : In article <583hkp$n7l@harbinger.cc.monash.edu.au>, pavan1@student.monash.edu.au (Paul van den Bergen) wrote:
: : >Howdy folks,
: : >Umongst other things I am a mineral collector, and I have been
: : >investigating setting up a UV fluoresence display.
: : >As such I am looking for suitable UV lights, esp. short wave UV.
: : >
: : >I have read a bit about the subject, and I know I need a low pressure
: : >mercury tube with a glass capable of transmitting below 240 nm (the
: : >strong Mercury UV line is around 255nm)
: : >I have a lamp with a soda-lime glass (comp.???), that gets down to 280
: : >nm, and I would really like to get the really short 180nm lines too
: : >For this I really need a fused silica bulb or tube, or an alumina tube
: : >(if they make them)
: : You probably need a deuterium lamp which emits UV mostly
: : from 180nm and up (with the main peak at 225nm). Try
: : Instruments S.A.Inc.,
: : JOBIN YVON/SPEX Division (France and US)
: : They also have a phone number in Germany: 89-4603001.
The leading producer of deuterium lamps is actually based in
the UK (Cathodeon Ltd, Nuffield Rd, Cambridge CB4 1TW,
tel +44 (0)1223 424100).
These D2 lamps are relatively cheap, and quite compact.
Many different sorts of glass envelope can be supplied.
They emit a beam of continuum UV in the 180-370nm range,
and are generally used in scientific instruments (spectro-
photometers and the like), and I'm not sure the above application
is practicable. They also have some power supply requirements.
A short-pulse strike voltage of 400-700V is necessary to strike
the discharge, while an operating voltage of 70V at 0.3A is
typical. A separate low voltage current source to heat the
cathode prior to striking must be also supplied.
-------------------------------------------
Glen Harris, Chemistry, Sheffield Univ, GB.
tel.: 44-114-2824518, fax: 44-114-2738673
email: g.r.harris@sheffield.ac.uk
www: http://www.shef.ac.uk/~ch1grh/
-------------------------------------------
Subject: Books forsale
From: wong@leconte.seas.ucla.edu (Ling S. Wong)
Date: Mon, 16 Dec 1996 14:54:07 GMT
Hi everyone,
I can't find the *.forsale group corresponding to this newsgroup.
So hopefully nobody is offended by my posting the forsale list here. If
someone is interested in several volumes then we could negotiate the
price. Thanks very much for your kind attention.
Lance Wong
301-613-0829
or reply to wong@enh.nist.gov
All books are in excellent to pristine conditions. Prices excludes postage.
TeX in Practice by von Bechtolsheim (4 volumes) $125
LaTeX (for 2e) by L. Lamport $ 16
NeXTSTEP Programming by Garfinkel & Mahoney $ 20
The TeXbook by D. Knuth (Hardcover) $30
Commands A-L, M-Z for SVR4.2; Unix Press $50
The Macintosh Bible 5/e by DiNucci, et al. $15
Principles & Applications of Organotransition Metal Chemistry by Collman, et
al. $25
Main Group Chemistry by Massey $25
Reacton mechanisms of inortganic and organometallic systems by Jordan $25
An introduction to ultrathin organic films (from L-B to Self-assembly) by
Ulman $35
Stereochemistry for Organic Compands by Eliel, et al. $35
Principles of Polymer Chemistry by Flory $45
Physical Chemistry by Adamson (5/e) $30
NMR of proteins & nucleic acids by Wuthrich $30
Electrode kinetics for chemists, chemical engineers, and material scientists
by Gileadi $35
Electrochemistry by Brett & Brett $20
Modern Electrochemistry 1 & 2 by Bockris & Reddy $30
Atomic & Molecular Spectroscopy by Svanberg $30
Writing the Lab. Notebook by Kanare (ACS) $8.
Subject: Charge on a capacitor
From: dlc@bhars90.bnr.co.uk (D L Chalmers)
Date: 16 Dec 1996 13:54:10 +0000
A simple problem which I came across in practically the first chapter of
an electromagnetic theory book (Reitz, Milford and Christy) - given two
infinite parallel conducting plates, one having charge +q, the other
having charge -q, how do you prove that the charges reside on the inside
of the plates ?
| |
| |
| |
| |
| |
|+q |
| |
| -q|
| |
| |
| |
| |
| |
My argument was as follows (given electric field inside each plate is
zero, and additive properties of electric field vector):
1. Introduce charge +q onto left hand plate - charge will distribute
evenly with +q/2 on one side and +q/2 on the other. Use Gauss's law to
show that right hand plate has charge -q/2 induced on its left side, and
+q/2 on its right side.
2. Introduce charge -q onto right hand plate - charge will distribute
evenly with -q/2 on one side and -q/2 on the other. Use Gauss's law to
show that left hand plate has charge +q/2 induced on its right side, and
-q/2 on its left side.
3. Add up charges to show that all charges cancel outside the capacitor,
with +q and -q remaining on the inside of the two plates.
Is there a simpler way ?
Also, this electrostatics stuff all seems a bit simplistic to me -
presumably in a real conductor (as opposed to one in a text book :-)),
the excess charges which have been added will slot into some part of the
conduction bands of the material. Presumably under certain conditions
(e.g. high temperature, filled bands - any others ?), the excess charges
will just fly off elsewhere and not be confined to the conductor. Is
this a fair comment ?
Does anyone have any idea of the numbers here - for example, I remember
at school rubbing plastic rods with wool and then transferring charges
with a little metal disc on the end of an insulating glass rod. What
would the typical amount of charge involved here be ? How much of that
would we be able to place on an isolated, room-temperature conductor and
how much would disappear into free space ?
Just curious ...
--
Regards,
Dave Chalmers
######################################################################
Broadband Development D.L.Chalmers@bnr.co.uk
Advanced Technology Centre +44 (0)1279 402150
Nortel, Harlow UK ESN 6 742 2150
######################################################################
Subject: Re: Physics GRE
From: candy@mildred.ph.utexas.edu (Jeff Candy)
Date: 16 Dec 1996 15:14:49 GMT
john baez:
|> Don't worry; at the rate the scores are declining we'll all be
|> able to get in by 2021.
My impression, after reading the last few posts to this thread, is
that the GRE has taken a step in the right direction. I wrote the
exam on a very cold, dreary december morning exactly seven years ago.
I've expressed the sentiment already that the exam was, in my opinion,
largely pointless -- about the worst way to judge incoming students.
Now I understand that these exams of six to seven years ago required
much less computation. At that time, the American students who passed
the exam by regurgitating trivia from Millikan's oil drop experiment,
and computing with blinding speed the de Broglie wavelength of an
electron, entered grad school without the ability to diagonalize
a matrix or find a Green function for some simple differential
operator.
-------------------------------------------------------------------
Jeff Candy The University of Texas at Austin
Institute for Fusion Studies Austin, Texas
-------------------------------------------------------------------
Subject: Re: Room Temperature Superconducting Powder
From: Jeff Norrell
Date: Mon, 16 Dec 1996 09:15:05 -0600
> This materal is believed to be a lithium beryllium hydride. I believe
> someone from Physics Dept of Purdue University has also been working on
> this. They may have more info.
To add a little more information, if no one has come across
this yet... Check out:
http://www.sciencenow.org/html/961212b.htm
What this story says is this:
Magnetic interactions have been observed but, as of
yet, conductivity hasn't been tested. Apparently, a grad
student got a bit overzealous during his doctoral defense,
implying that the material they had developed might be
a room temp. superconductor. A local reporter present put
the story out over Reuters, and it took off from there.
My question is this: After making this claim, how did
the rest of the student's defense go? :)
Jeff Norrell
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Jeff Norrell To err is human... To
University of Texas at Austin-Mad Lab really screw up requires
mail: norrell@utmems.me.utexas.edu the root password.
web: http://shimano.me.utexas.edu/~norrell
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Subject: Re: A case against nuclear energy?
From: TL ADAMS
Date: Mon, 16 Dec 1996 10:18:24 -0500
TL ADAMS wrote:
>
> DaveHatunen wrote:
> >
> > In article <32B34E46.2DC5@west.darkside.com>,
> > TL ADAMS wrote:
> > >DaveHatunen wrote:
>
> Killer of children, do not occuse an old blood of not telling
> truth. We do not take grave insults easily.
Oops, extremely poor judgement on my part Dave, for which I do
heartily apol. Sometimes my inherent distrust of white eyes comes to
the surface. Plus, it Monday Morning and I haven't had my four
cups of coffee yet.
Once again, I should have not met insult with insult, and I greviously
overstepped good taste. Sorry.
Subject: Re: Power output comparison
From: Anthony Potts
Date: Mon, 16 Dec 1996 15:14:31 GMT
On 16 Dec 1996, Hauke Reddmann wrote:
> A Saturn V rocket has a big power output, but a
> big mass too. When you compare a human, a horse,
> a car, a plane, ..., is P/m roughly constant?
> Or maybe a power :-) law P^a/m^b=c should apply?
> Anyone with some actual data?
> --
I don't know about per unit mass, but per unit volume, humans put out more
power than the sun does.
Anthony Potts
CERN, Geneva
Subject: Re: A case against nuclear energy?
From: jac@ibms46.scri.fsu.edu (Jim Carr)
Date: 16 Dec 1996 00:05:34 GMT
TL ADAMS writes:
>
>Me, I say put the stuff into the salt domes, alot safer than the
>crap that is leaking now. Fifty years into the program, and
>still no perm solution.
If every person concerned about nuclear waste felt as TL does,
the political obstacles to an interim solution would not have
delayed that project long enough for technical objections to
crop up. There are some real concerns about the use of salt
now, but the biggest problem is getting the stuff there.
My own favorite is the "put it back where it came from" solution.
The original U ore was radioactive and buried until we mined it.
So put equivalently radioactive materials, perhaps glassified,
back in those same holes. The current plans have in mind a system
where one can go back in and remove and reprocess if there is a
problem during the initial phases, which is why the concentrations
are higher and the risk of leakage greater.
Simply "burning" the stuff is even better, but the political
opposition to that is even greater than the arguments that are
keeping it all in the tanks next to the river.
--
James A. Carr | "The half of knowledge is knowing
http://www.scri.fsu.edu/~jac/ | where to find knowledge" - Anon.
Supercomputer Computations Res. Inst. | Motto over the entrance to Dodd
Florida State, Tallahassee FL 32306 | Hall, former library at FSCW.
Subject: Re: A few dark matter questions
From: pcp2g@karma.astro.Virginia.EDU (Twisted STISter)
Date: Mon, 16 Dec 1996 15:29:21 GMT
In article <58tctc$5fb@agate.berkeley.edu>,
Mark Rajesh Das wrote:
>
> Lemme begin by saying I'm not expert and so bear with me if I got
>some things wrong.
>
> The way I understand it, dark matter (dm) was concocted to 'correct'
>the problem with the rotation of our galaxy vs. the mass
>concentration with respect to the distance from our galaxy's center.
There are two basic reasons to assume there is lots of dark matter.
One is that the rotation curve of many galaxies (the plot of stellar
orbital velocity versus distance from the galactic center) indicates that
there is lots of mass outside the galaxy that cannot be seen. If the
mass were not there, then you expect the orbital velocities to drop
with distance, like planets in the solar system (Pluto orbits the
Sun more slowly than Mercury does). However, the curve flattens out
with distance, which you expect if there is a massive halo outside the
visible galaxy. Also, many spirlas (including our own) have a warp, or
bend in the disk. This warp is a natural outcome of a massive halo.
The Andromeda galaxy has a pronounced warp. Find a picture of it
(there are a million on the net) and draw a line through the galaxy along
its axis. You'll see the edges tip way up from that line.
The other reason to suspect dark matter exists involves clusters of
galaxies. We can measure the average speed of all the galaxies in
the cluster, and then also estimate a mass given the amount of light
emitted by the cluster. We find that the amount of mass is only
about 10% what is needed to account for the velocities of the
individual galaxies. Therefore there must be a LOT of mass we cannot
see in the cluster.
>First question. We're near the edge of our galaxy, why don't we notice
>any dark matter around us? Given that it makes ~9/10 the total mass
>and probably more locally, since we're in an area of greater concentration,
>there should be loads of dark matter.
If it is composed of planet-like objects in the halo we cannot see them
They can be detected through gravitational lensing (do a net search
on that term to find a description of how it works), but not directly.
Hell, we still cant detect planets around nearby stars, but that will
change over the next few years.
>2) one of the going theories is that WIMPS (neutrinos?) from stars
>makes up for some or all of the dark matter. If that's the case,
>why would there be a halo? Shouldn't most dark matter be near the
>center as that's where the greatest concentration of stars is?
It depends on the actual formation mechanism of the galaxy. Note that
99% of the mass of the solar system is in the center (the Sun), but that
most of the objects by number (comets) are way the hell out from the
center.
>2a) there's alot of debate on whether neutrinos, a possible candidate
>for (dm) are massless or not. Whether they is or ain't, someone
>pointed out to me that they still attract objects gravitationally. So
>what's the big deal if they ain't?
There was some debate on that here a few months ago, wasn't there?
I am not that familiar with gravity from massless particles.
>3) if dm is a halo and is massive, shouldn't the matter we can see
>be distorted so that our galaxy would have a bright ring where
>the stars are being pulled in by the dm halo? (when I say "matter ...
>distorted" I mean shouldn't the concentration of matter be distorted.
>Apologies for the wording)
See what I said about warps in the disk above!
>There was talk about gravity not working the way we think it does
>that either at large distances it falls off differently then we
>theorize presently. Anything to this?
Every now and then someone talks about this, but there is little evidence for
it.
--
* Phil Plait, Pee Aytch Dee pcp2g@virginia.edu
* My home page-- http://www.astro.virginia.edu/~pcp2g/home.html
* --> Humor, supernovae, Bad Astronomy, Mad Science
* and my daughter Zoe.
Subject: Re: Mind-time (Re: faster than light travel)
From: blair@trojan.neta.com (Blair P Houghton)
Date: 16 Dec 1996 09:31:01 -0700
Jonathan Silverlight wrote:
>Blair P Houghton (blair@trojan.neta.com) writes:
>>Our minds in certain circumstances are uncannily
>>accurate at temporal tasks. We don't have an innate
>>sense of enumerated time, but those of us who are
>>well-coordinated are capable of impressive feats.
>>
>>Juggling, quarterbacking, comedy, and music are obvious
>>examples of ways our minds can apply time with precision.
>
>I'm probably missing something obvious, but can you tell me why any
>of these require knowledge of "objective" or clock time ? I don't
>see that a comedian knows that his routine runs for (say) 1.00
>minute, and music is often played at different speeds.
You're missing something obvous. "We don't have an innate
sense of enumerated time". And our sense of time gets less
accurate for anything longer than a few seconds.
We do understand objective time, though (i.e., timespans
which appear the same to two observers). A quarterback
needs to be able to perform timed patterns to his
receivers. Comedians time setup and punchline to cause the
maximum effect in the audience. And I've seen a juggler
keep a machete, a running chainsaw, and a flaming torch in
the air all at once. I'm sure his limbs appreciate his
rhythm.
--Blair
"Time is on my side."
-the Stones
