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Conservation of momentum of a colliding car

  1. May 24, 2009 #1
    1. The problem statement, all variables and given/known data
    A 1200 kg car moving eastward at 8 m/s approaches an intersection where it unfortunately collides with an 1800 kg car going southward at 6 m/s. If they stick together, how fast do they move after the collision? The answer is 4.82 m/s


    2. Relevant equations
    a^2+b^2=c^2, p=mv, p before + p before = p after + p after


    3. The attempt at a solution
    V=mv+mv/m+m
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 24, 2009 #2

    LowlyPion

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    I think you will want to resolve the momentum into x,y momentum equations and determine the x,y velocity components, before using the Pythagorean.
     
  4. May 25, 2009 #3
    how do i determine the velocity components?? i can get the momentum components easily by multiplying the velocity and mass...right?
     
  5. May 25, 2009 #4

    LowlyPion

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    The car going East is can be be expressed as

    M1V1 = M1*|V1| x + 0 y = 1200*8 x = 9600 x

    And the one going south ...

    M2V2 = 0 x + M2*|V2| y = 1800*(-6) y = - 10800 y

    Now you have an inelastic collision, so in the X direction

    9600 = V'*(1200 + 1800) x = 9600/3000 x

    and so on until you have the 2 components of the final V'.
     
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