Search   Memberlist   Usergroups
 Page 27 of 28 [416 Posts] View previous topic :: View next topic Goto page:  Previous  1, 2, 3, ..., 25, 26, 27, 28 Next
Author Message
guskz@hotmail.com
science forum Guru

Joined: 30 Dec 2005
Posts: 663

Posted: Sun Feb 12, 2006 2:19 pm    Post subject: Re: I need more Brain Juice here

guskz@hotmail.com wrote:
 Quote: guskz@hotmail.com wrote: Smitty Two wrote: In article <1139707828.129690.207500@g14g2000cwa.googlegroups.com>, "guskz@hotmail.com" wrote: A brick laying on a sloped book?? the only thing preventing it from sliding down the book would be friction? Therefore if the sloped book was more vertical than sloped then the brick would slide down unto the table? As for the brick pushing down on my finger, no if the friction is enough to keep the brick in place on the sloped book??? Yes, the only thing keeping the brick in place is friction, but that's not relevant to the analogy. And yes, the brick on the slope doesn't push down on your finger. Do you see the correlation with the water in the cone? Think of your finger as the water in the section of tubing below the cone, and the sloping book as a part of the sloped section of cone wall. The water on the sloping cone wall doesn't push down on the water in the tubing anymore than the brick pushes down on your finger, which is not at all. You just said that friction is holding the brick in place?? Add more than one brick (same as the water in the cone) and the brick will push down on the finger. They already gave me the answer which is the horizontal force of the adjacent water particles (linked to the opposite cone wall) cancels the downward force. Same as: On the opposite side of the brick on the slope there is more books stacked on top of each other.

Mistake: not books stacked on top of each other but bricks instead
(since the brick represent the water particles and the book represents
the cone's wall).

 Quote: These books

These bricks (water particles)

 Quote: would be pushed horizontally by the brick as it slides down, but they do not since they are laying this force on the opposite wall of the cone (another sloped book at their opposite end) and therefore the brick does not slide down or put pressure on the finger below it anymore. If that still doesn't make sense, then you may need more brain juice after all. Or perhaps someone who's a better teacher than I.
Billy H
science forum beginner

Joined: 30 Nov 2005
Posts: 42

 Posted: Sun Feb 19, 2006 7:22 pm    Post subject: Re: Elementary CHARGE (+ OR -), {e}. Could someon please tell me where this entire thread can be found? -- Billy H With a blob of grease here and a bit of weld under there. If you don't do it right it'll fall apart next year. When your foot goes through the floor, and the skin falls of the door, When your Weals fall off, it'll make you Mohr than cough. It's dead fright'ning.
Stuart A. Bronstein
science forum beginner

Joined: 02 Mar 2006
Posts: 4

Posted: Sat Mar 04, 2006 6:56 am    Post subject: Re: Bad shimmy upon heavy braking Toyota 4Runner (why?)

"Dick Boyd" <dickboyd@aol.com> wrote in
 Quote: AFAIK, there is a standard for almost everything EXCEPT brake friction materials and rotors.

Hi Dick,

Thank you for the wonderful explanation of the purpose and intent of
these federal motor vehicle safety standards. Your explanation gives
reason to why there isn't a standard for brake materials.

Basically, we can conclude two astounding things from this wonderful
discussion.

1. The lack of standards for friction materials should not harm OEM
braking performance because there are standards for OEM braking systems!

2. Because of that, we should be VERY CAREFUL about putting non OEM
parts on our automobiles & trucks as there are no standards for non OEM
applications!

This is truly an enlightening and non-obvious discussion!
Thanks for helping out!

Stu

"Dick Boyd" <dickboyd@aol.com> wrote in

Gregory L. Hansen
science forum Guru

Joined: 04 May 2005
Posts: 771

Posted: Sun Mar 05, 2006 3:53 pm    Post subject: Re: Couple moments = free vectors?

In article <iLudnaLM9erOSpTZRVn-jw@comcast.com>,
David Corliss <dcorliss@ieee.org> wrote:
 Quote: ......... So how does a vehicular wheel work? You need to generate a net translational force at the axle. You have a frictional force,say f, at the road surface contact point. Assume that at a given instant, a single spoke is a massless rod, say of length r, connecting the axle and the frictional road force. There would be a torque moment, T, at the wheel axle, being supplied via the drive train. Would the net translational force be (T-rf)/r? ... just summing moments on the spoke and dividing by r.

I'm not entirely sure what you're asking.

Torque is r cross f. Or, for a wheel on the road, we can dispense with
the cross products and say T=rf. The drive train gives us some T, the
wheel has an r, so the force on the road is f=T/r.

If you mean a case where the car (and the wheel) is accelerating, the
moments of inertia of the wheels won't mean much compared with the mass of
the car. But torques add (mind the signs).

T = I a

where T is the net torque, I the moment of inertia, and a the angular
acceleration instead of using the customary Greek letter alpha. Or, for
an accelerating wheel,

T_d + T_r = I a

where T_d is the torque from the drivetrain, T_r is the torque from the

T_d - rf = I a

And solve for f or a or whatever you had in mind.

 Quote: "Gregory L. Hansen" wrote in message news:ducahd$73j$3@rainier.uits.indiana.edu... In article <1141436806.217276.154090@z34g2000cwc.googlegroups.com>, kenneth.bull@gmail.com> wrote: Hello, I am learning (engineering) mechanics. It took me a while to somewhat understand the idea of moments (torques). If a force is applied to a point on a body, then the moment about different points are based on the moment arm distance from those points to the force. Thus, the moment about different points on the body are, in general, not equal. Then now I've enountered COUPLE MOMENTS. Moments caused by couples (2 forces equal in magnitude, opposite in sense, and parallel to each other). These moments are "free vectors" that can be moved around on the body, and affect each point on the body equally (is this right?). So I'm wondering if "EACH MOLECULE" in the body feels the same moment (tendency to rotate) caused by a resultant couple moments. Is this what is meant by "free vector"? After encountering couple moments, it has destroyed my confidence in normal moments too. Can someone cofirm that what I've explained about is right? DO I have it wrong? Anyone know a good explanation of couple moments they can give me? Thank you very much Coupled moments are just two torques. Suppose you have two masses, m, connected by a massless rod of length L. (I don't know about you engineers, but we physicists always keep a drawer full of frictionless pulleys, massless rods, and other apparatus of the sort.) Apply a force F at a distance r from mass 1, and the torque about mass 1 will be T=F*r*sin(angle). The torque about mass 2 will be T=-F*(L-r)*sin(angle). If r=L/2 the system will not rotate because there will be equal and opposite torques. It will simply translate. Throw in two forces separated by a distance 2a with their center of separation at a distance r from mass 1. Then the torque about mass 1 would be T = F*(r-a)*sin(angle) - F*(r+a)*sin(angle) = -2 F a sin(angle) r disappeared. You can maybe understand that better as a->0, because then you'll have two forces that exactly cancel each other out. Or you could think of it as one force acting as the fulcrum for another force. The angular acceleration is not independent of r. But then the angular acceleration is proportional to the moment of inertia, which goes as r^2. If you change our dumbbell to a lollipop with a massless handle, the moment of inertia is simply I=mr^2. Angular acceleration goes as T=Ia, so we'd have a = T/mr^2 The longer the handle is, the slower the acceleration, as you'd expect, while the torque is constant. -- "He who only sees business in business is a fool."

--
"The polhode rolls without slipping on the herpolhode lying in the
invariable plane." -- Goldstein, Classical Mechanics 2nd. ed., p207.
Billy H
science forum beginner

Joined: 30 Nov 2005
Posts: 42

Posted: Sun Mar 05, 2006 6:41 pm    Post subject: Re: Hi Fi tools

"Tony Jeffree" <tony@jeffree.co.uk> wrote in message
 Quote: On Sun, 5 Feb 2006 22:49:53 -0000, "Billy H" nospam.nanteshoward@nanteshoward.f9.co.uk.nospam> wrote: I think it is the Stilsons, closely followed by the Spanner. Anyone? What about the brain. Is that a high fidelity tool? Only when it has been carefully adjusted by the skilled application of a Stilson... ;-)

It just struck me that'd hurt.

 Quote: Regards, Tony
brian a m stuckless
science forum Guru

Joined: 31 Aug 2005
Posts: 2024

Posted: Fri Mar 17, 2006 11:06 am    Post subject: Re: Solution to Einstein's Field Equations where T^uv not= 0?.

Jay R. Yablon wrote: >
 Quote: Many of the widely-studied solutions to Einstein's field equations are taken in vacuo, that is, at events where the energy momentum tensor T^uv=0. This includes Schwarzchild and Kerr geometries, for example. Have there been many exact solutions found where T^uv not= 0? $$No. I am speaking of analytical solutions where the differential equations are solved exactly, *not* numerical approximations.$$ YABsolutely no.

 Quote: Maxwell's energy tensor of electrodynamics T^u_v = (1/4pi) [F^ut F_vt - (1/4) lambda^u_v F^st F_st]. -=- ..interested in solutions where F^uv_u=0 (free space) -=- ..and where F^uv_u=J^v (space with current sources). Conditions of interest include static spherical symmetry in the nature of Schwarzchild, and rotation with spherical symmetry about the z-axis in the nature of Kerr. --Jay R Yablon. To be clear, I am *not* looking for solutions where the metric is assumed to be a Minkowski metric. Lots of analyses assume a flat-space background for electrodynamics. Rather, I am looking for *exact* solutions, to the extent that such solutions are known, which derive a curved spacetime metric from the electromagnetic field strength tensor, that is, which derive g_uv = g_uv(F^uv) via the Maxwell tensor T^u_v, whereby T^u_v(g_uv, F_uv) simply becomes T^u_v(F_uv) once the g_uv(F^uv) are found.

$$Maxwell used REAL "flat" plates in air to derive his equations.$$ This is why GR is only "approximately" flat, at-great-distance.
$$Even a dot has extreme "curvature", so you can imagine a point.$$ GR is a "point-SURFACE manifold" at the end of it's WORLD-line.
$$This is why GR is NOT a "local" theory (where it's all Newton).$$ This is why GR is a "far-field" theory (where it's all Newton).
$$[ The "SURFACE" of a GR-"POiNT" is "FLAT-at-a-GREAT-distance ].$$
$$Tom R ought derive a set from lab work ..using "CURVED" plates.$$ [Just let the PLATEs be M1 and m1 and the air as the "AEther"].
 Hope this helps, `Brian A M Stuckless, Ph.T (Tivity).
GR CUT OFF it's own WORLD-line, having DECLARED no PRiOR geometry.
p.s. A GR-"geodesic" is *NOT* Uncle Al's "OTHER LONGER way round".

 Quote: Thanks.> > Jay R. Yablon > > Email: jyablon@nycap.rr.com Re: Solution to Einstein's Field Equations where T^uv not= 0?.
Timo de Beer
science forum beginner

Joined: 16 May 2005
Posts: 14

Posted: Tue Apr 04, 2006 9:24 pm    Post subject: Re: Sea Salt Produces Reflective Clouds

As a sideline, these salt crystals appear to form an important fraction of
the small dust particles that happen to be the environmental topic of the
day here in Holland (after a few building concessions being withheld for
fear of exceeding the allowable dust concentrations in residential areas).

Timo

"Bret Cahill" <BretCahill@aol.com> wrote in message
 Quote: That's why vehicles rust out just being parked anywhere near salt water. Just walk down the beach wearing glasses during an offshore wind. The sea salt idea might be adapted to bleed energy away from hurricanes. Bret Cahill
Ian Taylor
science forum beginner

Joined: 13 Jun 2005
Posts: 10

Posted: Mon May 01, 2006 10:53 am    Post subject: Re: TIRED OF HIGH GAS PRICES ?

Move to Europe.

Maybe you will then realise how cheap your gas really is !!!
N:dlzc D:aol T:com (dlzc)
science forum Guru

Joined: 25 Mar 2005
Posts: 2835

Posted: Mon May 01, 2006 1:05 pm    Post subject: Re: TIRED OF HIGH GAS PRICES ?

Dear Ian Taylor:

"Ian Taylor" <robert.ian.taylor@gmail.com> wrote in message
 Quote: Move to Europe. Maybe you will then realise how cheap your gas really is !!!

Gas in Russia was really cheap...

David A. Smith
brian a m stuckless
science forum Guru

Joined: 31 Aug 2005
Posts: 2024

Posted: Tue May 23, 2006 7:47 am    Post subject: Re: What is the logic behind "negative binding" energy??

$$Tom [He between his error-bars] Roberts [..@GR.Buffy.com] wrote:  Quote: In order for a system consisting of multiple constituents to be bound as a single system, it must not fly apart on its own. That is, in order to disassemble the system you must somehow reach into it and _pull_ one or more constituents out of the system (of course this requires you to somehow hold on to some of the other constituents). In pulling it apart you of course do work, which is putting energy into the constituents of the system. The total amount of work you must do to completely disassemble the system is minus the binding energy of the system. That _is_ the way it was originally defined, and since you must do positive work to disassemble it, binding energy is inherently negative. Equivalently, when assembling the system an amount of energy must be released, which is also minus the binding energy. For example, in Newtonian gravitation, the gravitational potential \phi for a point mass M is -kM/r (k is Newton's gravitational constant). The minus sign is essential, because the force _must_ be -grad phi. The minus sign in this last equation is essential, because the force _must_ be directed away from regions of higher potential energy. Remember that gravitation is attractive and energy is conserved -- these two properties completely determine those minus signs. So a system that is gravitationally bound has negative potential energy, and it is quite appropriate to equate this to the binding energy of the system (disassembling it means separating the masses to infinity, where the gravitational potential energy is zero, as is the binding energy). In relativity, applying E=mc^2 in the rest frame of the system, and always disassembling it into components at rest far away in that frame, the mass of the system is simply the sum of: a) the masses of its constituents, b) their kinetic energies (while part of the system), and c) the binding energy. Note if binding energy were positive there would be a funny minus sign in there. Tom [He between his error-bars] Roberts [..@GR.Buffy.com].$$ You lack a distinction between "Total ENERGY" & "Total ENTHALPY".
$$[LaGrangian L; intrinsic REST energy eM; Volt*Amp*sec energy eV].$$
$$GUESS iSS STANDARD TOTAL ENTHALPY E = m*c^2 + pL*c + pA*fA$$ = eM + L + eV
$$= eM + L + nA*hbar*fA$$ = eM + Kinetic energy eK
$$..Note, *total-OTHERwise-ENERGY*... = eM + L - (m*v^2 / 2).$$
$$Where kinetic energy eK is the photoelectric "iONization energy".$$ [This energy is NOT ONLY particular to the photoelectric effect].
 STANDARD Total ENTHALPY ..NO "funny minus sign in there", Dimwit.
Don Lancaster
science forum beginner

Joined: 26 Nov 2005
Posts: 32

Posted: Wed May 24, 2006 3:39 pm    Post subject: Re: Properties of HHO (aka Aquygen, Brown's Gas, Klein's gas, etc)

PV wrote:
 Quote: Don Lancaster writes: I haven't seen this last one - is it a single large LED, or a composite like the ones they put in traffic lights? 1400 watts must be a freaking huge LED. * Links on http://www.tinaja.com/whtnu06.asp yeah, I found the manufacturer after a little googling. Apparently they aren't actually making the 28,000 lumen light engine yet (it is a composite). Still, the way thing are going incandescents are going to be completely gone inside of 5 years. While searching, I found several places selling bulb replacements. For 30 bucks you get a bulb that lasts for 10 years continuous use, and uses like 5 watts for the equivalent of a 75 watt bulb. Great stuff. *

What is neat is the potential 2X or so efficiency improvement over
fluorescents. Present LED limits are engineering and learning curve, not
physics.

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552

Please visit my GURU's LAIR web site at http://www.tinaja.com
Uncle Al
science forum Guru

Joined: 24 Mar 2005
Posts: 1226

Posted: Thu May 25, 2006 1:45 am    Post subject: Re: Mahmoud Ahmadinejad PhD (Eng.) President of Iran

Larry Hammick wrote:
 Quote: Uncle Al wrote: Iranian academia, if one can call it that, is important to Ahmadinejad. It's interesting to watch how he manipulates and uses the Iranian student mob, of which he is a former member. In particular, he has chosen to deliver some of his more bloodthirsty addresses to student crowds. landnotloans@hotmail.com wrote: A short acedemic bio Source?

No, Uncle Al did not write that. LIAR.

Uncle Al suggested that a fruitful target for Iranian terrorism would
be 1111 Constitution Avenue, NW, Washington, DC 20224. That is the
IRS building. Internal Revenue has been terrorizing Americans for 70
years. Turnabout is fair play. Let's redistribute some income back.

Tell Uncle Al if you would be personally put out by a small fission
device ablating the Internal Revenue Service. Think of it as a social
audit. Uncle Al would break out a sealed bottle of Lagavulin, polish
the Waterford, and invite neighbors in for a celebratory tipple.

An asymmetric warfare act of stateless terrorism with an improvised
nuclear device directed against Internal Revenue would justify a new
national holiday. BTW, Lady Godiva rode naked through the streets of
Coventry to protest her husband's heinous taxation policies in 1040
AD. Give it to the IRS good and hard and listen to America cheer.

Government cannot award people what it first has not stolen from
them. What one man receives without effort is confiscated from
another who labors. The money I make belongs to me and my family, not
to a government stooge who takes a cut and dumps the rest on slum
bunnies for squirting out babies.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
larryhammick@telus.net
science forum Guru Wannabe

Joined: 14 Feb 2006
Posts: 217

 Posted: Thu May 25, 2006 2:26 am    Post subject: Re: Mahmoud Ahmadinejad PhD (Eng.) President of Iran On second thought, if you look at the carats > or whatever you're seeing, you'll see that the notorious troll Uncle Al has not been quoted at all. So you're reputation is safe, a*****le. And shove your tax beefs up your arse, fool.
Don Lancaster
science forum beginner

Joined: 26 Nov 2005
Posts: 32

Posted: Sat May 27, 2006 1:17 am    Post subject: Re: Properties of HHO (aka Aquygen, Brown's Gas, Klein's gas, etc)

 Quote: On Thu, 25 May 2006 21:20:00 +0100, Pooh Bear wrote: David Bostwick wrote: In article , Jan Panteltje wrote: Shut up moron. Oooh, he got you good, Nomad. So totally ! ;-) LEDs are becoming more and more common. True, you can't buy them as easily as incandescent or fluorescent, and they're pricier. I'll bet kerosene lanterns and candles were a lot more common than light bulbs for quite a while, too. Hey ! My house originally had gas lighting. Graham that new flangled electric lighting will never catch on.

Actually, there is every reason to believe that incandescent lighting
will shortly be legislated out of existence.

Anything under 80 Lumens per watt will eventually be a no-no.

http://www.tinaja.com/glib/energfun.pdf

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552

Please visit my GURU's LAIR web site at http://www.tinaja.com
Bret Cahill
science forum Guru

Joined: 05 May 2005
Posts: 480

 Posted: Fri Jun 23, 2006 7:23 am    Post subject: Re: New German 4 seater gets 157 MPG < The obstacles are safety-related. Only in a demolition derby do you need a heavy vehicle to be safe. In real life there are more intelligent ways to be much safer. Supposedly Ford and Microsoft are working on collision avoidance systems. I like the idea of a gyro unicycle that would automatically pogo stick over offending vehicles, execute a whimsical flip in mid air and then land in the emergency lane. Cops would never be able to give you a ticket because they would be laughing too hard. Bret Cahill

 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
 Page 27 of 28 [416 Posts] Goto page:  Previous  1, 2, 3, ..., 25, 26, 27, 28 Next View previous topic :: View next topic
 The time now is Fri Mar 22, 2019 3:49 am | All times are GMT
 Jump to: Select a forum-------------------Forum index|___Science and Technology    |___Math    |   |___Research    |   |___num-analysis    |   |___Symbolic    |   |___Combinatorics    |   |___Probability    |   |   |___Prediction    |   |       |   |___Undergraduate    |   |___Recreational    |       |___Physics    |   |___Research    |   |___New Theories    |   |___Acoustics    |   |___Electromagnetics    |   |___Strings    |   |___Particle    |   |___Fusion    |   |___Relativity    |       |___Chem    |   |___Analytical    |   |___Electrochem    |   |   |___Battery    |   |       |   |___Coatings    |       |___Engineering        |___Control        |___Mechanics        |___Chemical

 Topic Author Forum Replies Last Post Similar Topics 10 Cent/Watt Solar Steam Engine; 70% Carnot From World's ... Bret Cahill Mechanics 0 Mon May 01, 2006 10:53 pm orion 4star meter waterpollutionlaboratory@ Analytical 0 Fri Apr 07, 2006 1:41 pm So does anyone else see the meter definition as silly Spaceman Mechanics 41 Tue Feb 14, 2006 12:29 am static-grounding of meter movements? dances_with_barkadas@yaho Control 23 Fri Feb 10, 2006 9:01 pm pH meter site Borek Chem 4 Thu Dec 15, 2005 11:48 pm