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2-D motion help

  1. Feb 10, 2007 #1
    A particle's trajectory is defined as x = (1/2t^3 - 2t^2) m and y = (1/2t^2 - 2t)m where t is in s.

    What is the particle's direction of motion, measured from the x axis, at t=0 and t= 3.5, measured in degrees counterclockwise from the x axis.

    I started out by plugging in t = 0 and t = 3.5 to the equations given. I then attemped to take arctan(y/x) in both cases to find the direction of motion. my answers for these, 0 degrees and 15.9 degrees respectively, both came back as wrong.

    Any clues as to what I am doing wrong/how to do it right?
  2. jcsd
  3. Feb 10, 2007 #2


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    If you used the given equations, then you have found the LOCATION of the particle. What can you do to get information about the velocity of the particle?
  4. Feb 10, 2007 #3
    Try differentiaing wrt t (for both x and y separately) to find the general equations for velocity.
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