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Homework Help: Find the angle of acceleration in circular motion

  1. Oct 21, 2011 #1
    1. The problem statement, all variables and given/known data
    Find the direction of acceleration relative to
    the direction of motion. Answer between −180°
    and 180°.

    The tangential acceleration is .98 m/s2. The centripital acceleration is 2.205m/s2

    Answer in units of °

    2. Relevant equations
    3. The attempt at a solution

    I tried tan( 2.205/.98) but this does not seem right at all. Could you also explain how you got the answer and why it works.

    Thanks in advance
  2. jcsd
  3. Oct 21, 2011 #2
    Don't you mean arctan rather than tan? Tan need degrees. 2.205/.98 is not degrees.
  4. Oct 21, 2011 #3
    So does that mean the answer is 66.03°
  5. Oct 22, 2011 #4
    That is the arctan of 2.205/.98 so you computed the correct angle. It's 66.04 degrees measured from the tangential acceleration vector. It is pointing in the general direction of tangential acceleration but moreso towards the inside of the arc because the magnitude of the centripital acceleration is the larger of the two accelerations. If you draw the vectors to scale and place them head to tail and close the right triangle, you'll see where the resultant it is pointing.
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