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Ek = Eg question

  1. May 5, 2009 #1
    1. The problem statement, all variables and given/known data
    you throw a ball directly upward, giving it an initial velocity of 10.0 m/s. neglecting friction, what would be the maximum height of the ball? (explain why you do not need to know the mass of the ball)



    2. Relevant equations
    now the problem itself i understand.

    we need Eg=mgh, Ek=1/2mv^2



    3. The attempt at a solution
    Ek=Eg
    1/2mv^2 = mgh
    1/2v^2 = gh
    1/2(10.0)^2 = 9.81h
    50/9.81 = h
    h = 5.1m

    i understand that we do not have mass and so it must cancel out, but i am confused as to why we do not need to know the mass?
     
  2. jcsd
  3. May 5, 2009 #2

    Cyosis

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    What falls faster a feather or a cannon ball? (this problem assumes 0 resistance)
     
  4. May 5, 2009 #3
    neglecting air friction, neither..
    meaning mass doesnt matter
     
  5. May 5, 2009 #4

    Cyosis

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    So you're saying that gravity accelerates all masses in an equal manner. This is correct. What is the one force acting upon the ball after you release it?
     
  6. May 5, 2009 #5
    only gravity (in this instance because it says to neglect friction)
     
  7. May 5, 2009 #6

    Cyosis

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    Yes, do you understand now why you don't need to know the mass of the ball?
     
  8. May 5, 2009 #7
    i understand.
    thank you
     
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