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Homework Help: Motion Q.

  1. Sep 10, 2007 #1
    1. The problem statement, all variables and given/known data

    A toy train is pushed forward and released at x_0 = 2.0 m with
    a speed of 2.0 m/s. It rolls at a steady speed for 2.0 s, then one
    wheel begins to stick. The train comes to a stop 6.0 m from the
    point at which it was released. What is the magnitude of the
    train’s acceleration after its wheel begins to stick?

    2. Relevant equations

    x_f = x_i +v*t +(1/2)*a*t^2

    3. The attempt at a solution

    O, well, I guess my attempt is this:

    at x_0 = 2 m
    v_0 = 2m/s
    a_0 = 0 m/s^2

    at x_1 = 6 m
    v_1 = 2 m/s
    a_0 = 0 m/s^2

    and finally, through the relevant equation above,

    8 = 6 + (2)(t) + (1/2)(a*t^2)

    I have no idea how to complete this from here. Help?
  2. jcsd
  3. Sep 10, 2007 #2


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    Homework Helper

    Use a different kinematics equation.
  4. Sep 10, 2007 #3
    Well, okay, how about

    v_f^2 = v_i^2 + 2*a*x

    0 = (4) +2*a*(2)

    -4 = 4*a

    a = -1 m/s^2

    so the magnitude of the acceleration is 1 m/s^2. But it can't be this simple now can it?
  5. Sep 10, 2007 #4


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    Homework Helper

    That looks right to me.
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