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Particle problem, velocity and acceleration

  1. Sep 7, 2009 #1
    1. The problem statement, all variables and given/known data

    The position of a particle moving along the x axis depends on the time according to the equation x = ct4 - bt8, where x is in meters and t in seconds. Let c and b have numerical values 2.4 m/s4 and 1.9 m/s8, respectively. From t = 0.0 s to t = 1.3 s, (a) what is the displacement of the particle? Find its velocity at times (b) 1.0 s, (c) 2.0 s, (d) 3.0 s, and (e) 4.0 s. Find its acceleration at (f) 1.0 s, (g) 2.0 s, (h) 3.0 s, and (i) 4.0 s.

    2. Relevant equations

    x = ct4 - bt8

    v= disp/time

    v=vo + at

    3. The attempt at a solution

    i got part a correct, i know the displacement is -8.64 meters
    what i'm really having trouble with.. is the idea that the problem clearly states that the time interval is 0 to 1.3 seconds.. and then it asks you to find velocity and acceleration for up to 4 seconds. how is this done? i know that you can't just do v= disp/time using -8.64 meters/1 second for part b, because it said the answer was wrong. please help?
  2. jcsd
  3. Sep 7, 2009 #2


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    This problem requires using calculus to take the derivative of x.
  4. Sep 7, 2009 #3
    is there any possible way that you could explain further?
  5. Sep 7, 2009 #4
    is it just.. that i take the first derivative of the function to find the velocities, and the 2nd derivative to find the acceleration?
  6. Sep 7, 2009 #5


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    Yes, exactly. Has that been covered in your class yet?
  7. Sep 7, 2009 #6
    honestly.. no. we've had 3 classes and i've learned absolutely nothing, other than the fact that my teacher knows how to throw a beanie baby up in the air...
  8. Sep 7, 2009 #7
    thank you very much for your help- i finally got the whole problem!
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