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Force acting on object of given coordinates

  1. Sep 23, 2009 #1
    1. The problem statement, all variables and given/known data

    3.0 kg object is moving in plane with x and y coordinates given by x=5t^2-1 and y=3t^2-2 where x and y are meters and t is seconds. Find magnitued of net force acting on object at t=2 seconds.

    2. Relevant equations

    (vectors above the letters where they normally go)
    a = ax + ay

    3. The attempt at a solution

    Taking the 2 equations, and differentiating to get the velocities functions, then again to get the acceleration functions I get (the i and j are "hats"):

    Vx = 10t i and ax = 10 i
    Vy = 6t i and ay = 6 j

    a = ax + ay and magnitude a = sqrt (ax^2 + ay^2) = sqrt (10^2 + 6^2) = sqrt (136) = 11.66 m/s^2

    Then inserting into F=ma:

    F = (3.0 kg)(11.66 m/s^2)
    F = 34.98 N

    And I can just ignore the "2 seconds" because the same constant force is acting? Or do I need to multiply that force by 2?

    Thank you for any guidance.
  2. jcsd
  3. Sep 23, 2009 #2


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    Homework Helper

    what you have looks to be correct.
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