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Homework Help: Deriving acceleration from a position function

  1. Aug 31, 2010 #1
    1. The problem statement, all variables and given/known data
    A particle moves along the y axis according to y(t)=(3.5 m/s2)t2 - (9.0 m/s)t + 5.0 m.
    (a) What is the particle's velocity as a function of time?
    (b) What is the particle's acceleration at t=2.0 s?

    3. The attempt at a solution

    I was wondering about b- I derived:
    dy/dt = (7 m/s2)t - 9.0 m/s for the velocity function
    and then
    dv/dt = 7 m/s2 for the acceleration function.

    So the acceleration is constant, right? I'm finding seemingly irrelevant questions make me paranoid.
  2. jcsd
  3. Aug 31, 2010 #2
    Yes, you just showed that the acceleration is constant. In fact you can check with a graphing calculator by applying the knowledge you learned in class.
    In fact when you graph the y(t) equation you get a upwards parabola. Then the v(t) graph will be a positive line. Thus the a(t) graph is constant.
    My calculator says you are right. :)
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