Hi Matt, At 12:56 a.m. 26/07/02 -0700, Matt Broze wrote: >No Way! The fuel in the rocket is a huge store of potential energy that when >released will propel the rocket far beyond it keeping the same center of >mass for it and its exhaust particles. This potential energy constitutes an >outside force. The laws of motion you are talking about concern collisions >between moving objects when no force beyond their existing masses and >momentums is present or introduced. Sorry to disagree with you. Fortunately enough my disagreement is more in the academic part of basic physics than in the part related to the paddle efficiency. The rocket principle and why it moves when in vacuum is a classical problem of first college gear in the mechanics class. I agree that there is a lot of potential energy inside the rocket. I agree that explosion liberates a lot of energy. But you can not refuse the universal law that in close systems unperturbed by external (by external I mean external) forces must maintain their state of momentum. In outer space vacuum there is no mass (almost), no friction and no drag. But the paradox is that rockets change their state of speed. How can that happen without violating the universal law of momentum conservation? It is only because m1v1 of particles or gasses (mass) going out in one direction equal m2v2 of rocket in the other. To be more precise, the change in momentum in one direction equals the change in momentum in the opposite direction, so that resultant momentum stays the same. Once it moves, the next particle expulsion occurs with a different state of momentum because the rocket has already some speed, and then some more speed is gained and so on. If you want I can make a deeper or more detailed comment off line. On the other hand the system kayak-paddler-paddle move with respect to the media (called water) by interacting with it. Therefore that is an external force. The system must get in touch with the external environment to gain any speed. Everything else in my discussion follows from these statements. Best Regards, Rafael Mier-Maza el cayuco chief *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Fri Jul 26 2002 - 09:35:42 PDT
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