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Homework Help: Work and conservation of energy

  1. Dec 11, 2004 #1
    okay i applied work and conservation of energy to this problem, but the solution doenst come out right! :mad:

    Suppose the roller coaster in the figure below passes point A with a speed of 1.76 m/s

    If the average force of friction is equal to one fifth of its weight, with what speed will it reach point B? The distance traveled is 45.8 m and h = 29.4 m.

    1/2mvi^2 + mgh - 1/5md = 1/2mvf^2

    the m's cancel out and u should be able to solve for Vf, but it doest come out right!
  2. jcsd
  3. Dec 11, 2004 #2


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    First your equation is wrong, because it says the force of friction is [itex] \frac{1}{5} [/itex] of its weight, so [itex] F_{f} = \frac{1}{5}mg [/itex] and the work done by friction [itex] W_{f} = - \frac{1}{5}mgd [/itex]
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