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!

Double the speed

  1. Oct 22, 2012 #1
    1. The problem statement, all variables and given/known data
    A proton is accelerated from rest through a potential difference of 500MV. Classical mechanics indicates that quadrupling the potential difference would double the speed. Were a classical analysis valid, what speed would result from a 2000MV potential difference?


    2. Relevant equations

    4V->2v

    3. The attempt at a solution
    We were first asked to find the original speed of the proton going through 500MV which is 0.76c Since 2000MV = 4*500MV and 4V means v is doubled, why can't I just double 0.76c to get the new speed for the proton accelerated through the 2000MV?
     
  2. jcsd
  3. Oct 22, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    I believe that you are asked to do precisely that.
     
  4. Oct 22, 2012 #3
    Yet the answer is 2.07c :/
     
  5. Oct 22, 2012 #4
    the book solves it by 4*(the original KE, 8*10^-11 J) = .5 * m * v^2 then solving for v.......but I really just don't see why I can't logically just straight-up double the velocity...
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook