Ballistic Theory, Progress report...Suitable for 5yo Kids
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From: Paul B. Andersen on 11 Nov 2005 08:36 Eric Gisse wrote: > Henri Wilson wrote: > >>On 8 Nov 2005 19:19:07 -0800, "Eric Gisse" <jowr.pi(a)gmail.com> wrote: >> >> >>>Jerry wrote: >>> >>>>Henri Wilson wrote: >>>> >>>>>On 8 Nov 2005 14:13:58 -0800, "Eric Gisse" <jowr.pi(a)gmail.com> wrote: >>>> >>>>>>So, E=mc^2 was not known before 1905. You cannot prove otherwise. >>>>> >>>>>It was obvious. >>>>>Just integrate mv.dv from 0 to c. What a stupid proposition. This integral gives the kinetic energy of a mass m going at the speed c, according to Newton. This has obviously nothing whatsoever to do with the energy content of a mass m at rest. >>>>Are you out to prove that well over two centuries in development >>>>of mathematics must be thrown out the window, the same as >>>>virtually all of physics? Shall we call your new system of >>>>mathematics wcalculus? >>> >>>int(mv,dv) = mv^2/2 >>> >>>Henri has shown many times he consideres being off by a factor of 1/2 >>>"close enough" to the real answer. >>> >>>I'm kinda getting tired of dealing with his idiocy, actually. >>>Mathematical subtilties like "being correct" are completely lost upon >>>him. >> >>can't you see where the other 1/2 comes from? > > > It is not my problem if you can't even work an integral. It is not my > job to invent explanations for *your* failures. The 1/2 is a bit beside the point anyway. The important point is that the E in E = mc^2 is not kinetic energy. Henry Wilson has no clue how to derive this equation. However, it may have been done before 1905, because it is possible to derive it using only Newtonian mechanics and Maxwell's equations. The following thought experiment was devised by Einstein, and is commonly referred to as "Einstein's box". I will describe it in my own words. Given a box with mass M and length L. From one side of the box, an EM radiation pulse with energy E is emitted. According to Maxwell, the momentum of the pulse is p = E/c. The time for the pulse to traverse the box is t = L/c. Conservation of momentum say that the box will move with the speed given by Mv = E/c, v = E/Mc while the pulse is on its way. When the pulse hits the other wall, the box is stopped. So the box has moved a distance d = vt = (E/c^2)L/M. But the mass-centre of the box must remain stationary. That means that a mass m must have moved along with the pulse so that m*L = M*d = (E/c^2)L Thus m = E/c^2 I think E = mc^2 follows from Maxwell's equations, EM-radiation has momentum. Paul
From: George Dishman on 11 Nov 2005 09:17 "Henri Wilson" <HW@..> wrote in message news:6ua7n15d9rn5rld9rco5lrfa752igqbdvs(a)4ax.com... > >>> On 9 Nov 2005 13:25:38 -0800, "George Dishman" >>> <george(a)briar.demon.co.uk> >>> wrote: >>>>> > >>>In Ritzian theory, the light is emitted at some speed greater >>>>> > >>>than c from the source. The speed can be found by taking the >>>>> > >>>magnitude of the vector sum of the mirror velocity and a >>>>> > >>>vector of magnitude c whose direction is such that the light >>>>> > >>>eventually reaches the detector. > > Consider this. > > You are driving along a road at v and your passenger wants to shoot a duck > that > is sitting on the ground 500 metres to your left. Where does he aim? > Where does he aim if the duck appears at 45 degree forward? > > Where does he aim if the duck flies off at v and exactly 90 degrees away > from > the road ? > > ____________v<-car > /gun > > > > > > | > | > | > \/ v > Duck You have it in a nutshell Henri. The only thing you missed is that the speed of the bullet is known relative to the gun but I'm sure you realise that. Now look at what I said. I'll change some terms to make it appropriate to your analogy: The speed [of the bullet across the ground] can be found by taking the magnitude of the vector sum of the [gun] velocity [over the ground] and a vector of magnitude [bullet speed relative to the gun] whose direction is such that the [bullet] eventually reaches the [duck]. I think that is pretty good agreement, don't you? George
From: Henri Wilson on 11 Nov 2005 17:30 On Fri, 11 Nov 2005 14:36:18 +0100, "Paul B. Andersen" <paul.b.andersen(a)hiadeletethis.no> wrote: >Eric Gisse wrote: >> Henri Wilson wrote: >> >>>On 8 Nov 2005 19:19:07 -0800, "Eric Gisse" <jowr.pi(a)gmail.com> wrote: >>> >>> >>>>Jerry wrote: >>>> >>>>>Henri Wilson wrote: >>>>> >>>>>>On 8 Nov 2005 14:13:58 -0800, "Eric Gisse" <jowr.pi(a)gmail.com> wrote: >>>>> >>>>>>>So, E=mc^2 was not known before 1905. You cannot prove otherwise. >>>>>> >>>>>>It was obvious. >>>>>>Just integrate mv.dv from 0 to c. > >What a stupid proposition. >This integral gives the kinetic energy of a mass >m going at the speed c, according to Newton. > >This has obviously nothing whatsoever to do >with the energy content of a mass m at rest. It might have. ....correct form. > >>>>>Are you out to prove that well over two centuries in development >>>>>of mathematics must be thrown out the window, the same as >>>>>virtually all of physics? Shall we call your new system of >>>>>mathematics wcalculus? >>>> >>>>int(mv,dv) = mv^2/2 >>>> >>>>Henri has shown many times he consideres being off by a factor of 1/2 >>>>"close enough" to the real answer. >>>> >>>>I'm kinda getting tired of dealing with his idiocy, actually. >>>>Mathematical subtilties like "being correct" are completely lost upon >>>>him. >>> >>>can't you see where the other 1/2 comes from? >> >> >> It is not my problem if you can't even work an integral. It is not my >> job to invent explanations for *your* failures. > >The 1/2 is a bit beside the point anyway. >The important point is that the E in E = mc^2 is not kinetic energy. > >Henry Wilson has no clue how to derive this equation. > >However, it may have been done before 1905, because >it is possible to derive it using only Newtonian mechanics >and Maxwell's equations. > >The following thought experiment was devised by Einstein, >and is commonly referred to as "Einstein's box". > >I will describe it in my own words. > >Given a box with mass M and length L. > From one side of the box, an EM radiation pulse >with energy E is emitted. According to Maxwell, >the momentum of the pulse is p = E/c. >The time for the pulse to traverse the box is t = L/c. >Conservation of momentum say that the box will move >with the speed given by Mv = E/c, v = E/Mc while the pulse >is on its way. When the pulse hits the other wall, the box >is stopped. >So the box has moved a distance d = vt = (E/c^2)L/M. >But the mass-centre of the box must remain stationary. >That means that a mass m must have moved along with the pulse >so that m*L = M*d = (E/c^2)L >Thus m = E/c^2 > >I think E = mc^2 follows from Maxwell's equations, >EM-radiation has momentum. > >Paul Geese will still want to argue. HW. www.users.bigpond.com/hewn/index.htm see: www.users.bigpond.com/hewn/variablestars.exe "Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong".
From: Henri Wilson on 11 Nov 2005 17:40 On Fri, 11 Nov 2005 10:49:02 +0100, "Paul B. Andersen" <paul.b.andersen(a)deletethishia.no> wrote: >Henri Wilson wrote: >> On Wed, 09 Nov 2005 23:50:03 +0100, "Paul B. Andersen" >> <paul.b.andersen(a)deletethishia.no> wrote: >> >>>It is a long time since fighters were stable. >>>They cannot be flown without a computer. >>>Not even close. >>>With traditional control, a man would simply not be fast enough >>>to keep control of the plane. >> >> >> Yes that is pretty obvious. > >Is it? >I am not convinced you have grasped the point. I do. One might compare this with the way a rocket is kept vertical during lift-off. >A traditional aircraft - say like a small Cessna - is stable. >That means that if the pilot leaves the aircraft to itself, >it will keep going straight ahead (provided that trim tabs etc. >are set properly). That means that if the plane by some reason >veers a little around one of its axes, it will automatically >correct itself. A non R/C model aircraft flies itself. >It can do that because it is inherently stable. Real aircrafts >are traditionally built after the same principles. >But modern fighters are inherently unstable. That means that >if it veers a little around one of its axes, forces will be >induced which make it veer more in the same direction, >unless it is corrected - fast! > >It could be compared to driving with a trailer. >While driving forward the trailer will automatically >follow the car. It is a stable system. But backing is another >story. If the trailer has a small angle to the car, >this angle will increase unless the driver corrects it. >It is impossible to back along a given curve without >continuous corrections on the steering wheel. It is >an unstable system. Paul I understand perfectly what you are saying. I still find it hard to believe, particularly when the plane is decelerating. >A modern fighter is like that. It can't go straight ahead >without continuous corrections. The article claims certain advantages in this...presumably less drag...OK... >A man is fast enough to back with a trailer - if he >drives slowly. But try to back at 100 km/h (60 mph)! >It can't be done. But a computer could. Yes Paul. I understand that. I still find it hard to believe that the plane is unstable in all situations. Perhaps it only becomes unstable above a certain speed. That I can accept. >>>And it probably isn't possible even if he were. >>>The control panels don't move as you would expect them to. >>>For example, the right and left elevator may move in opposite >>>direction. And the ailerons may move in the same direction. >>>And then there are those two extra control panels underneath >>>the plane. >>> >>> >>>>I think such a servo control system would only apply during fast maveuvering. >>> >>>It's much more than a servo control. >>>The pilot tells the plane what he want it to do, and the computer >>>figure out how to do it. For example, if you pull the stick hard, >>>it means up as fast as possible. The plane will then pull up as >>>fast as it can without structural damage. (The pilot may pass out, >>>but the plane will stay in one piece.) >> >> >> The pilot still has to think fast enough to make the plane do what he wants. > >Obviously. :-) > >> The electronics just carries out his instructions. > >No, it does much more than that. Even with no input from >the pilot, it must continuously correct for the plane's >tendency to veer off course. It is so bad that if it didn't, >the plane would after a short time go into spin. Yes, just as a vertical rocket will veer off course and crash if the nozzles aren't adjusted quickly enough. .. >>>>...but any remote electronic system must work on the principle of sensing and >>>>reducing an error. One of the big problems is to find a decent compromise >>>>between reaction time, senstivity and damping. One must prevent the thing from >>>>building up an oscillation. >>> >>>It's very different from traditional servo loops. >> >> >> Well its a bit like electronic power steering of a car(which hasn't been >> introduced yet) but the basic problems remain. > >"A bit like" maybe, but just a very small bit. :-) >It is a multi variable control system. >That means that a number of inputs (rotations around >and accelerations along the different axes) affects >a number of outputs (the angle of the different control >panels). It can not be divided into a number of >one input - one output control loops. >It's a beast of a control system. > >Which (- to a Norwegian's malicious pleasure -) was >demonstrated by the Swedish JAS fighter. It crashed >twice because the control system didn't work properly. > >http://www.nearlygood.com/video/crashlanding.html >The pilot survived - and crashed a second time >at an air show! He ejected, and survived again. >He is probably getting used to it! :-) As I said, I hope I never have to fly in one. > >Paul HW. www.users.bigpond.com/hewn/index.htm see: www.users.bigpond.com/hewn/variablestars.exe "Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong".
From: Henri Wilson on 11 Nov 2005 17:46
On Fri, 11 Nov 2005 14:17:16 -0000, "George Dishman" <george(a)briar.demon.co.uk> wrote: > >"Henri Wilson" <HW@..> wrote in message >news:6ua7n15d9rn5rld9rco5lrfa752igqbdvs(a)4ax.com... >> >>>> On 9 Nov 2005 13:25:38 -0800, "George Dishman" >>>> <george(a)briar.demon.co.uk> >>>> wrote: >>>>>> > >>>In Ritzian theory, the light is emitted at some speed greater >>>>>> > >>>than c from the source. The speed can be found by taking the >>>>>> > >>>magnitude of the vector sum of the mirror velocity and a >>>>>> > >>>vector of magnitude c whose direction is such that the light >>>>>> > >>>eventually reaches the detector. >> >> Consider this. >> >> You are driving along a road at v and your passenger wants to shoot a duck >> that >> is sitting on the ground 500 metres to your left. Where does he aim? >> Where does he aim if the duck appears at 45 degree forward? >> >> Where does he aim if the duck flies off at v and exactly 90 degrees away >> from >> the road ? >> >> ____________v<-car >> /gun >> >> >> >> >> >> | >> | >> | >> \/ v >> Duck > >You have it in a nutshell Henri. The only thing you missed >is that the speed of the bullet is known relative to the gun >but I'm sure you realise that. Now look at what I said. I'll >change some terms to make it appropriate to your analogy: > > The speed [of the bullet across the ground] can be found > by taking the magnitude of the vector sum of the [gun] > velocity [over the ground] and a vector of magnitude > [bullet speed relative to the gun] whose direction is > such that the [bullet] eventually reaches the [duck]. > >I think that is pretty good agreement, don't you? That is right.... and according to the BaTh, the time taken for a photon to reach the mirror is constant even though the path length changes. But sagnac does not refute the Bath for this reason. Under Bath, wavelength does not change with source speed. One can imagine the wavecrests being connected by tiny rods. Since the path lengths are different in both directions of sagnac, (the duck example shows that) the number of wavelengths between the source and the mirror is not the same in each beam... The number varies with table rotation speed. That'll make you think... > >George > HW. www.users.bigpond.com/hewn/index.htm see: www.users.bigpond.com/hewn/variablestars.exe "Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong". |