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Homework Help: Conservation of Energy rollercoaster

  1. Jul 9, 2006 #1
    I have a quetion that I worked out and would love to know if I worked it out alright. Here it goes...

    A roller coaster of mass 80kg is moving with a speed of 20.0 m/s at position A with a height of 200m. There is no friction and g=10m/s^2.

    So basically theres a diagram of a rollercoaster with different points and different heights.

    What is the total energy of the rollercoaster at point A?

    So, this is at the top of the rollercoaster, so I basically calculated the potential energy. (mass)*(g)*(height).

    Next, what is the total energy of the roller coaster at point B, which has no height.

    I calculated the kinetic energy 1/2(mass)(v)^2 and got 1600J

    Did I do this correct?
  2. jcsd
  3. Jul 9, 2006 #2


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    Aren't you forgetting the initial kinetic energy? HINT: Is energy conserved?
  4. Jul 9, 2006 #3


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    Hello jhrnndz1,

    you've missed that the roller coaster has kinetic energy at point A as well.


  5. Jul 10, 2006 #4
    Energy conservation states that total potential + total kinetic = total energy, PE + KE = TE. For your question, TE at point A is 0.5(80)(20)^2 + 80(10)(200) = 176 KJ. At point B, when the roller coaster comes down, its TE is still the same as its PE is converted to KE, thus the roller coaster will have a greater KE, meaning more speed.
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