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Magnitude of Impulse

  1. Oct 7, 2013 #1
    1. The problem statement, all variables and given/known data
    What is the magnitude of the Impulse exerted on a 920-kg car as it slows from 24.3 m/s to 12.9 m/s while traveling in a straight line?

    3. The attempt at a solution
    I was thinking 920(24.3 m/s) and 920(12.9 m/s) and subtract the two.

    Not totally sure tho.
  2. jcsd
  3. Oct 7, 2013 #2
    The Impulse in classical mechanics can be understood as the average force multiplied by the time it is exerted.

    J = Faverage (t2 - t1 )

    J = ∫ F dt , evaluated from t1 to t2

    since F is related to the change in momentum with respect to time,

    J = ∫ (dp/dt) dt , evaluated from t1 to t2

    here, the dt's cancel, and you get,

    J = ∫ dp , evaluated from P1 to P2

    so, finally you get to J = p2 - p1 = ΔP

    You suggested subtracting the two. Make sure to subtract them in the correct order to obtain the correct sign.
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