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Easy momentum question

  1. Apr 16, 2009 #1
    1. The problem statement, all variables and given/known data
    A 30.00 kg mass falls from a height of 4.00m. The momentum of the mass just before it hits the ground is?


    2. Relevant equations

    obviously p=mv

    3. The attempt at a solution

    I just can't figure out how to get a velocity for this formula?
     
  2. jcsd
  3. Apr 16, 2009 #2

    LowlyPion

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    Homework Helper

    Consider one of these kinematic equations:
    https://www.physicsforums.com/showpost.php?p=905663&postcount=2
     
  4. Apr 16, 2009 #3

    Matterwave

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    Science Advisor
    Gold Member

    There are 2 ways to do this.

    1) Find the velocity using kinematic equations:
    [tex]x = \frac{1}{2}gt^2[/tex]
    you know x and g so you can solve for t. After solving for t you can get the velocity from [tex]v=gt[/tex].

    2) You can also use energy conservation
    [tex]KE=\frac{1}{2}mv^2=PE=mgh[/tex]
    and then applying the knowledge of what KE is and momentum is
    [tex]KE=\frac{p^2}{2m}[/tex]
    to find p directly.
     
  5. Apr 16, 2009 #4
    yes sir that helped me figure out what the book got, thanks a bunch!
     
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