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*To*: KellySt@aol.com, hous0042@maroon.tc.umn.edu, stevev@efn.org, rddesign@wolfenet.com, RUSSESS@cellpro.cellpro.com, jim@bogie2.bio.purdue.edu, zkulpa@zmit1.ippt.gov.pl*Subject*: Engineering Newsletter*From*: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)*Date*: Wed, 22 Nov 1995 18:18:59 +0100

ReplyTo : Steve and Kevin ReplyFrom: Timothy >I say that "relativistic mass increase" is a misnomer and that >you are better off treating mass as invariant. Both methods are valid to use. The difference is more a physical matter than a mathematical. I was used to working with the "wrong" formulas and Steve was used working with the "right" formulas. The so called "wrong" formulas look a bit more like the classic formulas so they may be easier to understand. Both methods are being taught at universities and both are valid. I've always looked at is as follows: When you move faster and faster, part of the energy is transformed into mass, the other part is used to get the extra momentum. Now I only wonder, does such a fast moving particle excert greater gravitation on a non-moving observer? Steve if the answer is yes, how do you explain that not using "relativistic mass increase"? >Timothy uses a different convention for the angle than I did. >His math is correct using his convention. I was measuring a >relative to normal of the mirror plane rather than relative to >the surface. Yeps, it seems I'm a bit odd, doing that. >A reflected photon transfers momentum to a reflector normal to >the reflecting surface. An absorbed photon transfers momentum in >the direction and magnitude of the the photon's original >momentum. This is the only consistent way to preserve >conservation of momentum in both cases. Yes, this is what I tried to explain from the start, but due to misunderstandings I was not able to get to the point earlier. >Fundamental principle of relativistic mechanics: The momenergy >(vector quantity of energy and momentum of a system) is conserved >within the system through all interactions of the system >components. Or as I wrote earlier: Once more, whatever ingenious construction you can think of, to receive a certain amount of photons and use their energy, you ALWAYS get ALL their momentum in the same direction as they went to. ReplyTo : Kevin ReplyFrom: Timothy Here are some answers to the remaining part of your letter: >> Ah, do I get it right if I think you mean that the sail absorbs the photons? >> And that you think that if the photons are absorbed at an angle the forward >> momentum is less than if the photons are absorbed perpendicular? > >Yes, That seems right. Let me try again. So I finally understand... (Now I wonder how you turn a perfectly reflecting sail in an perfect absorber) >> I only have a fague idea of how this works. A Skottky diode is just a fast > ^^^^^ >I'm not trying to flame you Tim, I think you meant "vague" >and since you're not sure either, Let's wait to hear from someone who is. I don't mind people telling me how to write better English. Since it is not my native language I'm almost certain to be doomed to make mistakes. To: Ric Hedman Writing long mails is OK, but to write 4 lines and quote the other 250 lines seems a bit too much. Timothy

**Follow-Ups**:**Engineering Newsletter***From:*Steve VanDevender <stevev@efn.org>

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