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Homework Help: A body thrown upwards with some external force

  1. Feb 5, 2016 #1
    1. The problem statement, all variables and given/known data
    A ball of mass of 1Kg is held in hand. The moment it is released from hand, without any delay it is hit by an external force of 100N in upwards direction. How high will the body go ?

    2. Relevant equations

    3. The attempt at a solution
    I know how to solve if instead of Force we consider initial velocity, then it becomes a standard problem.
  2. jcsd
  3. Feb 5, 2016 #2


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    Science Advisor

    Did this problem come from a textbook? Or is it a problem you came up with on your own?

    As it stands, there is not enough information to answer the question.
  4. Feb 5, 2016 #3


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    Homework Helper

    This sounds like an impulse problem:
    From (https://en.wikipedia.org/wiki/Newton's_laws_of_motion#Newton.27s_second_law)

    An impulse J occurs when a force F acts over an interval of time Δt, and it is given by:
    Since force is the time derivative of momentum, it follows that
    This relation between impulse and momentum is closer to Newton's wording of the second law.
    Impulse is a concept frequently used in the analysis of collisions and impacts."

    This should tell you what the instantaneous change in velocity should be from in impulse of 100N.
  5. Feb 5, 2016 #4
    I created it on my own.
  6. Feb 5, 2016 #5


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    Knowing the upward force is not enough to know how fast an object will move. It can tell you how fast the object will accelerate. In order to know how fast it will move, you must also know for how long the force is applied.
  7. Feb 5, 2016 #6


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    Except that impulse is not measured in newtons. It is measured in newton-seconds.
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