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2D - Momentum Question, Grade 12 Canadian Physics

  1. Nov 5, 2011 #1
    1. The problem statement, all variables and given/known data
    2 cars collide at an intersection.
    one car which has a mass of 1,400kg has a velocity of 45 km/h;
    the other car has a mass of 1,300kg and has a velocity of 39 km/h[E]
    The cars has an inelastic collision. What are their velocity after the collision


    2. Relevant equations

    Conservation of momentum: P total = P total prime


    3. The attempt at a solution

    I have tried on numerous occasions but have not achieved the correct answer.

    The correct answer should be: "30 km/h [ 51 South of East.]

    I got the correct magnitude of the velocity which is 30 km/h. Easy enough, but i didn't get the degrees required. Additional vector diagram is appreciated.
     
  2. jcsd
  3. Nov 5, 2011 #2
    Try to draw the vector diagram for the initial total momentum of the system.
     
  4. Nov 5, 2011 #3
    @grzz I figured out what i did wrong. When i calculated for the theta of the vector triangle. I simply used the velocities. Instead i tried it with m(v) and it worked for me. Thanks.
     
  5. Nov 5, 2011 #4
    You just confirmed that it is the total momentum that is conserved and not the total velocity!
     
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