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Homework Help: Calculate initial speed and acceleration given position (on x-axis) and time

  1. Sep 10, 2010 #1
    1. The problem statement, all variables and given/known data

    Help! I have no idea where to begin for this!!!

    You are driving along a straight section of roadway (x-axis). You spot a police officer and apply the brakes, slowing down at a constant rate. Your positions (in meters) at successive time intervals of 0.465 s are tabulated below as function of time. (1) Calculate the initial speed (i.e., the speed at t=0, the time at which the brakes are first applied.). (2) Calculate your acceleration along the x-axis, ax.
    x (m) 5.00 21.94 38.25 53.93
    t (s) 0.000 0.465 0.930 1.395

    2. Relevant equations

    x = x0 + v0t + (1/2)at^2
    v = v0 + at
    v^2 = v0^2 + 2a(x-x0)

    3. The attempt at a solution
  2. jcsd
  3. Sep 10, 2010 #2


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    Homework Helper

    Hi towng34, welcome to PF.

    If t is the successive interval of time, then

    x1 = xo + vo(t) +1/2*a*t^2..........(1)

    x2 = xo + vo*(2t) +1/2* a*(2t)^2 ........(2)

    Find x2 - 2*x1 and solve for a. From that you can find vo.
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