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Another conservation of energy problem

  1. Feb 22, 2009 #1
    1. The problem statement, all variables and given/known data
    why is the gravitational potential energy of a ball equal to its kinetic energy


    2. Relevant equations
    KE=PE


    3. The attempt at a solution
    im really not sure, i think its because energy is conserved but i dont know why that is either
     
  2. jcsd
  3. Feb 22, 2009 #2
    Yes, it has to do with the conservation of energy. Think of it this way - If you hold a ball in your hand and drop it, the kinetic energy will equal the gravitational potential energy, because the ball cannot acquire energy from any other source. Gravity is the only thing pulling the ball down - no other force is going to help the ball fall.
     
  4. Feb 22, 2009 #3
    oh i understand now thanks
     
  5. Feb 22, 2009 #4

    LowlyPion

    User Avatar
    Homework Helper

    As stated it is not.

    The conservation of energy tells you however that the Δ in potential energy will manifest as a Δ in kinetic energy when a ball is released in a gravitational field.
     
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