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Collision question regarding mass loss

  1. Nov 22, 2006 #1
    This might be stupid but I was thinking, when two subatomic particles collide at very high speeds, they form a bigger particle whose mass is less than the sum of the smaller ones, and the mass lost transforms into energy as in Einstein´s equation E=mc2.
    What happens with non subatomic particles, say two balls colliding or whatever. Is there a mass loss that turns into energy. THIS SOUNDS VERY OFF LOL, because the amount of energy released with just a little bit of mass is huge. But then, what is wrong here? Why doesn't this happen, or if it does, why isn't it perceived?
     
  2. jcsd
  3. Nov 22, 2006 #2

    OlderDan

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    That depends on wether you are talking about the rest mass or the relativistic mass. The rest mass does not change unless the particles transform into other particles. The relativistic mass changes with speed. Not everyone likes the concept of relativistic mass, but it's been around a long time and will probably die a very slow death.

    http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html#c5
     
  4. Nov 23, 2006 #3
    OlderDan, is that your opinion or is it really dying? Why?

    I mean the part you said about relativistic mass having a slow death.
     
  5. Nov 24, 2006 #4

    OlderDan

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    It is not my area of expertise (come to think of it, I may not have one at all) but I have come across numerous references to the concept of relativistic mass as being unnecessary and not particlularly useful, including the quote from Einstein in the link I posted. It's easy enough to write gamma*m where gamma = 1/sqrt(1-v²/c²) and m is the rest mass when that particular combination appears in the equations instead of always putting the subscript on m_o when rest mass is indicated. But lots of people used m for relativistic mass for a long time, and you still see it in many references. It's just a matter of convention, not some difference in the physics. The energy expressed as E = sqrt[p²c² + (mc²)²] where m is the rest mass is generally more useful than E = mc² where m is the relativistic mass in analyzing relativistic systems.
     
    Last edited: Nov 24, 2006
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