1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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


    User Avatar
    Homework Helper

    That looks right to me.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook