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Homework Help: Mechanics Problem

  1. Jan 18, 2015 #1
    1. The problem statement, all variables and given/known data
    ax=0.500 m/s^2
    Incline plane=9 m
    second incline plane=15m
    v1=0m/s(object starts at rest
    Problem also is uploaded
    2. Relevant equations

    3. The attempt at a solution
    For part A.

    1. Since ax=0.5m/s^2,
    2. .5(m/s^2)/9m=.055555551/s^2
    3. Invert: (.055555551/s^2)^-1=18s^2
    4. sqrt: 18s^2=4.24 s
    5. Plug in: Get 2.1 m/s

    The answer is supposed to be 3.00 m/s. Is there suppose to be a different way of setting it up.

    Attached Files:

  2. jcsd
  3. Jan 18, 2015 #2


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    Homework Helper

    Although you made the dimensions correct, this is not a valid way of finding the final speed.
    What is your interpretation of the acceleration divided by the distance? (It seems rather meaningless to me)

    This is how I would do it:
    Call the unknown final speed "V"
    In terms of V, (and the given acceleration) how long will it take to reach the bottom?
    In terms of V, what is the average velocity of the ball?
    If you multiply the average velocity and the time it took, what should the answer come out to be?
  4. Jan 19, 2015 #3


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    Gold Member

    Actually it is valid, and arises from a standard SUVAT equation. However, there's a constant factor missing. G. Coder, what equation did you base that on? It's not the one you quoted.
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