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Homework Help: Force given by a vector

  1. Oct 14, 2008 #1
    The force acting on a object ( 10 kg ) as function of time is given by :

    F (t) = [ (-20t + 90)i - 60j + ( 10t + 40)k ] Newton

    At time t=0 seconds , the speed of the object is given by :

    V = [-14i + 26j + 32k ] m/s

    question a )

    use the impulse-momentum theorem for deciding the objects speed at t=4 ?

    question B )

    What is the average force acting on the object in the time interval t=0 -> t=4 ?

    I can probably solve this task , but when I must use the theorem , I kind of get stuck

    No examples of the use of this have I found online , not in textbook either
  2. jcsd
  3. Oct 14, 2008 #2


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    Welcome to PF!

    Hi kennien! Welcome to PF! :smile:

    The impulse-momentum theorem is the impulse version of Newton's second law, F = d(mv)/dt.

    Instead of force = rate of change of momentum (the ordinary version), the impulse version is impulse = total change of momentum (I = m∆v). :wink:
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