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Verification needed - Rollar Coaster

  1. Oct 24, 2006 #1
    Bare with me guys as I enlist your help through this worksheet. I really want to get a good grade on this upcoming test and this worksheet is our study guide.

    I think I have the hang off it but I want to make sure I am grasping the questions here.

    A rollar coaster is traveling on a horizontal track at 20 m/s. What is its speed after climbing the second hill.

    I understand this to be an Ei=Ef problem.

    Here is my work:

    1/2MVi^2 = 1/2MVf^2 + GH ( all the mass variables cancel out )
    1/2(20)^2 = 1/2(Vf)^2 + (9.8)(15)
    200 = 1/2(Vf)^2 + 147
    53 = 1/2(Vf)^2
    53*2 = Vf^2
    106 = Vf^2
    Sq rt 106 is 10 m/s = Vf

    am I close? Please let me know.. I want the right answer but I also want to comperhend whats going with these. Just wanted you to know I am not looking for someone to do my work.. just nudge me along ;)

    (got one for you too after this, also.... a coeffencient of friction.. that one I will need someone to walk me through)
  2. jcsd
  3. Oct 24, 2006 #2
    Please provide the complete question when seeking help. Without having any info about "the second hill," we can't do much. One can only assume that it's peak is at a height of 15m above the horizontal track from your work. If that is so, your work is right. You may want to be a little more accurate with the final answer, though (to one or two decimal places).
  4. Oct 24, 2006 #3
    LOL.. I thought the same thing about this question.. as with most..LOL

    That was the entire question. You can see my fret over this problem..

    With the decimals places I would say 10.0 instead of 10 ??

    Looks good though??
  5. Oct 24, 2006 #4
    So where did you get that 15 from?

    I actually meant something like 10.2 or 10.29, which is a better approximation to sqrt(106) than 10 is.
  6. Oct 25, 2006 #5
    ohh.. I see.. the second hill is 15m high.. i apolize for that.

    Does my work look right?
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