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Homework Help: Velocity x components

  1. Nov 13, 2007 #1
    1. The problem statement, all variables and given/known data

    In a crash test a car with a mass of 1273kg collides with a wall. The x components of the initial and final speeds of the car are 22 m/s and 2.2 m/s. If the crash lasts for .16s what is the magnitude of impulse?

    2. Relevant equations

    impulse= change in momentum
    change in momentum = m(Vf-Vi)

    3. The attempt at a solution

    So the first thing I think I need is change in momentum which equals = m(Vf-Vi) however, I don't understand how you get the final and initial velocity when they only gave you the x components. Does it have something to do with using the Pythagorean theorem?
  2. jcsd
  3. Nov 13, 2007 #2
    You're right, change in momentum would be the first order of business. The crash test car is only going forwards (or possibly backwards, but that doesn't happen in this case)...the car is moving in a straight line. Therefore, you're only going to have X components. There is not any change in elevation, so X component is your only one.
  4. Nov 13, 2007 #3
    so it would be 1273(2.2-22) =-25205
  5. Nov 13, 2007 #4
    Well I believe you'll need to times that figure by .16 seconds (that's your delta time)
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