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Homework Help: Gravitational potential energy increase

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data

    A person weighing 6.0 × 102 newtons rides an
    elevator upward at an average speed of 3.0 meters
    per second for 5.0 seconds. How much does this
    person’s gravitational potential energy increase
    as a result of this ride?
    (1) 3.6 × 102 J (3) 3.0 × 103 J
    (2) 1.8 × 103 J (4) 9.0 × 103 J

    2. Relevant equations

    PE=mgh, KE=1/2mx^2
    3. The attempt at a solution
    I tried solving the question this way but it seems am wrong.... mgh=1/2mx^2 and I arrived at number '3'. Need help!!
  2. jcsd
  3. Jan 14, 2010 #2
    U = mgh ... that is about all you'll need (you know m and g, you just need to solve for the displacement).
  4. Jan 14, 2010 #3
    wat is U?
  5. Jan 14, 2010 #4
    wat is U?
  6. Jan 14, 2010 #5
    Potential Energy=mass*g*height

    Your approach can't be used in this type of problem. If you wanted to find the speed of a car at the bottom of a hill, you can set the two equations equal to each other (PE for the top, KE, for the bottom).

    Try finding the three parts of the equation Gear300 posted...you just need to solve for height (or displacement).
  7. Jan 14, 2010 #6
    thanx a bunch, just realized my blunder...
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