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Homework Help: Rock Problem Part 2

  1. Jan 25, 2006 #1
    This is the second hardest question on my test, how long does it take to push a rock 10m.

    50Kg rock
    10 m is the distance
    0.16m/s2 is the acceleration

    Does anyone know which kinematics equation I should use for this problem.
  2. jcsd
  3. Jan 25, 2006 #2
    The four kinematic equations are:

    d = vi*t + 1/2*a*t2

    vf = vi + a*t

    vf2 = vi2 + 2*a*d

    d = vi + vf/2 *t

    You want to pick the equation that has a "t" in it, and the one that has the most of your information already provided.

    P.S. your initial velocity is 0 m/s, remember! :wink:
  4. Jan 26, 2006 #3
    I know its the first equation since i have all the information except for t, but i'm not good at rearranging question so can you help me just a bit more. Really appreciate it.
  5. Jan 26, 2006 #4
    ok, so lets substitute the values for what we "know"

    d = vi*t + 1/2*a*t2, which would equal:

    10 = (0)*t + 1/2*(.16)*t2

    we want to try and solve for t, in the first part of the equation, (0)*t, we know that equals 0, so we can get rid of that part, now our equation is:

    10 = 1/2*(.16)*t2

    can you take it from there?
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