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Homework Help: Required force to stop a moving object.

  1. Jun 4, 2013 #1
    1. The problem statement, all variables and given/known data
    A solid object of 6kg was moving at a constant speed of 10m/s towards a man who try to stop it.
    If the man stopped the train in 30 seconds, find the force F that the man exerted on the object.

    3. The attempt at a solution
    The only force acting on the object is the man's force so : ma=-F, this means that : v(t)=v(0)-F t /m.
    We know that v(30)=0, wich means that : F= m*v(0)/30 = 2.

    Is my solution correct ? (I don't have anyone to ask him so I'm asking you).
  2. jcsd
  3. Jun 4, 2013 #2


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    Gold Member

    Seems fine, but put in units.
  4. Jun 4, 2013 #3
    An alternative (and easier) way of doing this is to use the impulse-momentum theorem.
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