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Homework Help: Simple Constant Acceleration/Directional problemWhat Am I doing wrong!

  1. Mar 30, 2008 #1
    1. The problem statement, all variables and given/known data
    A fish swimming in a horizontal plane has a velocity Vi=(4i +1j) m/s at a point in the ocean where the position relative to a certain rock is ri = (10i -4j)m. After the fish swims with constant acceleration for 20.0s, its velocity is v=(20i -5j) m/s.
    a.) What are the components of the acceleration?
    B.) What is the direction of the acceleration with respect to unit vector i? C.) If the fish maintains constant acceleration, where is it at t= 25s, and in what direction is it moving?

    2. Relevant equations
    The fact of the matter is we have constant acceleration, which means that the average acceleration is equal to the instantaneous acceleration. Also we know the equation for Aavg= Ainst= Delta V/Delta T = Vf-Vi/Tf-Ti OR we can use the kinematics equation: Vf=Vi+at, therefore Vf-Vi/T = a. So I did that , got the right answer I hope.

    The part that bugs me is B, what do they mean by the direcion of the acceleration with respect to unit vector i. Unit vector i is just the x component, so it'll always be either east or west. The answer is some angle measurement? Do I find the resultant? I tried for the last hour with every variation, trying to find resultant vectors, to just adding/subtracting the individual x component vectors. Can someone outline what I'm supposed to do here?
    Last edited: Mar 30, 2008
  2. jcsd
  3. Mar 30, 2008 #2


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    Homework Helper

    Hi HelpMeWIN123! :smile:

    The clue is in the word "direction".

    All they want is a direction.

    And they want you to specify it by its angle from a particular direction … in this case, i. :smile:
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