I need help calculating the impact speed of a positron and ?electron starting at 5 cm apart
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From: JohnF on 10 May 2010 04:23 In sci.physics Llanzlan Klazmon <bill.m.thomas(a)gmail.com> wrote: > On May 10, 4:38?pm, franklinhu <frankli...(a)yahoo.com> wrote: >> Let's say we have a positron and electron at rest with respect to each >> other. Since they are oppositely charged, they are immediately >> attracted to each other and begin to accelerate toward each other. At >> any point in the path, you can calculate the force between them using >> Columbs law, based on that, you could calculate the acceleration, but >> how do you calculate what would be the velocity of the positron and >> electron as they approach each other and then collide from some >> starting distance like 5cm? As distance approaches zero, the force >> approaches infinity. Does this mean that the velocity may approach >> infinity due to the infinite force acting on a mass or is there some >> limiting mechanism? Please help? >> >> -thanks >> fhuemc > > They will annihilate each other before they hit. Maybe so, but that doesn't really seem to be the intent of the question, i.e., the op seems to be assuming idealized charged point particles. If they were uncharged point masses under gravitational attraction, I'd suggest calculating their initial gravitational potential energy, and calculating final velocities assuming it's all converted to kinetic energy and the center of mass's velocity remains unchanged. But charged particles radiate as they accelerate (gravitational radiation usually being ignorable), so the calculation's more difficult than the op probably had in mind. -- John Forkosh ( mailto: j(a)f.com where j=john and f=forkosh ) |