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Homework Help: Urgent (PlEaSe) Kinetic Energy

  1. Nov 8, 2007 #1
    1. The problem statement, all variables and given/known data

    A sled and rider with a combined mass of 55 kg are at the top of a hill a height of 20 m above the level ground below. The sled is given a push providing an initial kinetic energy at the top of the hill of 1950 J.

    (c) If friction can be ignored, what will be the kinetic energy of the sled and rider be at the bottom of the hill?

    2. Relevant equations

    k = 1/2 m v (squared)

    3. The attempt at a solution

    1/5 x 55 x 20 (squared) = 11,000

    But its wrong!
  2. jcsd
  3. Nov 8, 2007 #2


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    Science Advisor
    Homework Helper

    V is the velocity not the height.
    At the top of the hill the sledge has potential energy given by "m g h" this is converted into kinetic energy as it goes down the hill, and is added to the intial KE
    You don't need to know the speed - athough you can work it out at the top and bottom if you like!
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