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Homework Help: Please help with Mechanical Energy Question

  1. Feb 4, 2010 #1
    Please help.... with Mechanical Energy Question

    1. The problem statement, all variables and given/known data

    A 0.50 kg rubber ball is thrown into the air. At a height of 20 m above the ground, it is traveling at 15 m/s.
    a. what is the balls kinetic energy
    b. What is its gravitational potential energy relative to the ground?
    c. how much work was done by someone at ground level throwing the ball into the air?
    d. What was the speed of the ball when it left the ground?


    3. The attempt at a solution

    a. Ek = 1/2 mv2
    Ek = 1/2 (0.50kg)(15m/s)
    Ek = 1/2 (0.50 kg)(225 m2/s2)
    Ek = 1/2 (112.5 J)
    Ek = 56 J

    b. Eg = mgh
    Eg = (0.50kg)(9.80 N/kg)(20m)
    Eg = 98 J

    c. W = fd
    HELP ME PLEASE
     
  2. jcsd
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