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Homework Help: Momentum, collision problem

  1. Mar 28, 2009 #1
    1. The problem statement, all variables and given/known data
    A car with a mass of 1680 kg is traveling directly northeast (45° between north and east) at a speed of 14 m/s (31 mph), and collides with a smaller car with a mass of 1300 kg that is traveling directly south at a speed of 13 m/s (29 mph). The two cars stick together during the collision. With what speed and direction does the tangled mess of metal move right after the collision?
    Magnitude __________ m/s
    Direction _________ degrees South of east

    2. Relevant equations
    m1v1i+m2v2i = v1(m1+m2)

    3. The attempt at a solution
    i tried plugging my values into this equation to figure out the answer but it doesnt seem to give me the right answer. im thinking maybe im doing it wrong becuase there is an angle involved but im not sure.
  2. jcsd
  3. Mar 28, 2009 #2


    User Avatar

    You're on the right track using conservation of momentum, but you seem to have forgotten that momentum is a vector quantity and therefore you will have an equation for the x-components and an equation fro the y-components. So, yes you need to make use of the angle.
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