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2-d collision problem

  1. Nov 2, 2013 #1
    1. The problem statement, all variables and given/known data
    A neutron of mass 1.7 X 10^-27 kg travelling at 2.2 km/s, hits a stationary helium nucleus of mass 6.6 X 10^-27 kg. After the collision, the velocity of the helium nucleus is 0.53 km/s at 52° to the original direction of motion of the neutron. Determine the final velocity of the neutron.


    2. Relevant equations

    pi1x+pi2x=pf1x+pf2x
    pi1y+pi2y=pf1y+pf2y

    3. The attempt at a solution

    I changed all the km/s to m/s since the answer is in m/s

    (1.7X10^-27(2200)-6.6X10^-27(530cos52))/1.7X10^-27=vficos∅
    933.18m/s=vficos∅

    Well, it does not matter what i get for the y component since the answer 1.9 m/s and 933 is just too high.
    So, is the answer wrong or did i do something wrong.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 2, 2013 #2

    TSny

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    I think the answer you were given should have been 1.9 km/s rather than 1.9 m/s.
     
  4. Nov 2, 2013 #3
    Well, I did solve it for km/s I got 1.05 km/s.
    vf2y=0.53sin52
    vf2y=0.418km/s
    vf2x=0.933 km/s

    If you use the Pythagorean theorem you get 1.05km/s
     
  5. Nov 3, 2013 #4

    TSny

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    You did not account for the masses of the particles in this calculation.
     
  6. Nov 3, 2013 #5
    You are right. How silly of me. Well, I got 1.9 km /m for my answer. Thanks for your help.
     
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