1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Relativistic CM frame Kinetic energy

  1. Apr 23, 2010 #1
    Now then, this is a past paper question for only 3 marks but its annoying me.

    2 identical spheres undergoing an elastic relativistic collision. The spheres move with a speed such that their CM frame kinetic energy is equal to their rest energy. Calculate the speed the spheres in the CM frame.
    Not entirely sure about this, i took the obvious option and calculated (root3/2)c as my speed.

    Any ideas?
    Thanks
     
  2. jcsd
  3. Apr 23, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi Bigfoots mum! :smile:

    (have a square-root: √ :wink:)
    Yes, that's the right answer :tongue2: …

    but how did you get it? :confused:
     
  4. Apr 23, 2010 #3
    I used Kinetic Energy T = E - mc^2

    where E is the total particle energy and mc^2 is the rest energy. Therefore gamma is 2, and we're away with the mixer.
    I just wasnt sure if this method would apply in the CM frame, but then im not sure why it wouldnt!
    Thanks for the response
     
  5. Apr 23, 2010 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    All your favourite formulas apply in any inertial frame. :biggrin:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook