Robin, don't beat yourself up too badly about having a short term mental block since it happens to all of us.
Energy can be conserved in an elastic collision such as you mentioned. Of course the momentum is modified in that case because the velocity changes direction. We started this discussion considering the operation of UFO type devices as an example. I have a difficult time accepting the fact that they might actually be controlled by something not human. That concept seems to be too fantastic to believe but I hope to realize the truth one day. The observation that these crafts appear to hover in the air silently and without emitting any form of exhaust leads some to consider reactionless drives as the source of the force that keeps them airborne. I do not feel that this is necessary since the earth could easily form the other side of the thrust equation. If the ship has some means of pushing against the earth, then it would be able to balance out the momentum and energy equations that have precipitated the recent discussion. We know for instance that a loop of wire carrying a large AC current can be repelled by any nearby metal surface. The amount of radiation exiting that wire can be quite small if the drive is at a low AC frequency. The near field effects induce a current within the metal surface that generates a force that holds up the loop. A power source on board the loop driven ship could be used to supply the current that allows the device to float above the metal surface. Now, back to the UFO and Earth situation. An observer on the Earth might not see the complete picture and could well assume that the ship emits no exhaust or mass of any kind. Of course we know that the Earth is being repelled away from the ship and supplies that mass. Momentum is conserved and all of the energy can likely be accounted for. I say likely since I have not taken the time required to prove it although I would be surprised to find out otherwise. I of course have serious doubts that a simple magnetic drive would actually generate the force required to keep one of those crafts afloat, but the concept of using the Earth as the other side of the thrust equation might work with another force. A method of manipulating gravity appears like the ideal solution. Dave -----Original Message----- From: mixent <[email protected]> To: vortex-l <[email protected]> Sent: Sat, Nov 29, 2014 7:10 pm Subject: Re: [Vo]:They call me a moron. A reply. In reply to David Roberson's message of Fri, 28 Nov 2014 23:24:51 -0500: Hi Dave, [snip] >OK, I have read several of those physics books and my position is sound. The formula for kinetic energy as seen by an observer is E=1/2*M*V*V. That V is not a difference, but the final relative velocity. If you want to find out how much the kinetic energy changes you must calculate the value of kinetic energy both before and then after the drive is applied. At that point you can find the delta in energy and you obtain the correct value according to physics. > >How about looking at the problem from a different perspective. Let the velocity change in two steps of 1 meter per second each. According to your procedure the kinetic energy is 2 times the amount gained in a single step since the same delta in velocity is determined for each one. You are correct. My mistake was in thinking that the change in kinetic energy had to be the same for all observers. This is not so. I do spout nonsense sometimes. Thanks for keeping me on the straight and narrow. :) > >In the other case the kinetic energy is the same both before and after the drive is enabled. The value is 1/2*1*1*M before the drive is enabled and 1/2*-1*-1*M after it completes its task. This is because the magnitude of the relative velocity is the same both before and then after the drive finishes. The sign changes, but that does not enter into the equation for kinetic energy since energy is a scalar. ... but if momentum can be exchanged, then changing direction need not cost any energy. (e.g. a marble bouncing on a hard surface approaches this condition.) Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
