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Homework Help: Speed of Rollercoaster

  1. Jul 27, 2011 #1
    1. The problem statement, all variables and given/known data
    The roller-coaster car shown in Fig. 6-41 (h1 = 50 m, h2 = 13 m, h3 = 25 m), is dragged up to point 1 where it is released from rest. Assuming no friction, calculate the speed at points 2, 3, and 4.
    6-41alt.gif


    2. Relevant equations
    v2= Square Root of 2*Gravity*Height


    3. The attempt at a solution
    I used the formula to figure out the speed at point 2( which was 31.304 m/s) but it doesn't seem like the same formula works for points 3 and 4 so I'm guessing I need another formula to figure out the other 2 points, although I have no clue what that might be.
     
  2. jcsd
  3. Jul 27, 2011 #2

    rock.freak667

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    Homework Helper

    From 1 to 2, the cart is released from rest at maximum height h1.

    So the total energy is the PE at point 1.

    If you want the energy conversion between 1 and 3 then you need to see that the PE at point 3 would include the change in PE from 1 to 3 and the KE at 3.

    Use conservation of energy to get this speed.
     
  4. Jul 28, 2011 #3

    PeterO

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    mis-leading equation here. the reference to height should say "change of height"

    For Point 2, the change of height is h₁

    For point 3, the change of height is (h₁ - h₃)

    For Point 4, the change of height is (h₁ - h₂)


    Peter
     
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