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Homework Help: Motion on Incline

  1. Feb 1, 2010 #1
    1. The problem statement, all variables and given/known data

    A ball is allowed to roll from rest down an inclined plane, and the distances are marked every 1.6 s. If the second mark is made 1.4 m from the starting point, where is the first mark?

    Where is the Fourth Mark?

    2. Relevant equations

    x=kt^2 .. k is the constant that I need to figure out to answer the questions.

    t = 4 x 1.6s for the 2nd part of the question

    3. The attempt at a solution

    I'm confused with what variables to plug in in order to answer the question.

    t is obviously 1.6s, but I don't know the X.
    1.4 = k1.6^2 = 1.4 = k2.56 ... 1.4 / 2.56 = k .. 0.55 = k .. Not correct. I need this K in order to find the solution to the 2nd problem
  2. jcsd
  3. Feb 1, 2010 #2


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    Homework Helper

    Welcome to PF!

    I think the ball will roll with constant acceleration so your x = ktĀ² should be right. Very clever of you to see that, or guess it.

    You are interested in two sets of data:
    1) d = ?, t = 1.6
    2) d = 1.4, t = 3.2
    In the second one, you know both d and t so you can plug them into the formula and find the k. Then apply the formula with the known value of k to the first set to find its d.
  4. Feb 8, 2010 #3
    Thanks for the help Delphi! :) (Sorry for my lateness, but wanted to show my gratitude)
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