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Homework Help: Comparing Velocities through Kinetic Energy

  1. Nov 7, 2015 #1
    1. The problem statement, all variables and given/known data
    An oxygen atom is 3.00 times as massive as a helium atom. In an experiment, a helium atom and an oxygen atom have the same kinetic energy. What is the ratio VHe/VO?

    2. Relevant equations
    KE = 1/2 mv^2

    3. The attempt at a solution
    I know KE for helium is = 1/2 mv^2
    and KE for Oxygen is = 1/2 3mv^2

    and KE are the same so

    1/2 mv^2 = 1/2 3mv^2

    Now im having trouble isolating and solving for v, they seem to just cancel out
  2. jcsd
  3. Nov 7, 2015 #2

    Ray Vickson

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    You have two different atoms, so need two different v's.
  4. Nov 7, 2015 #3
    1/2 mv^2 = 1/2 3mu^2

    Ok denoting them differently u = sqrt(1/3 mv^2) how do i get a ratio of v/u?
  5. Nov 7, 2015 #4


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    Have you studied algebra?
  6. Nov 7, 2015 #5
    Sorry hadn't realized i made the mistake

    v = sqrt3 * u
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