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Magnitude of average acceleration?

  1. Oct 11, 2011 #1
    I haven't done anything Physics related in 2 years (highschool) and am trying to get back into being familiar with Physics, Science, and mathematical terms for an upcoming class.

    1. The problem statement, all variables and given/known data

    A gazelle starts from rest and runs in a straight line 29° north of west. After 36s of running in this direction, the gazelle has a speed of 12 m/s. (a) What is the magnitude of the gazelle's average acceleration? Assuming that north and east are the positive directions, find the component of the horse's acceleration that points alone (b) the north - south line and (c) the east-west line.


    2. Relevant equations

    I know you have to do an initial equation by subtracting the animal's moving speed from the resting speed but from there I have no idea what to do. If someone could give me the correct formula, I can work the rest out myself.
     
  2. jcsd
  3. Oct 11, 2011 #2

    SammyS

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    What is the definition for average acceleration?
     
  4. Oct 11, 2011 #3
    From my notes I have a = Δv / Δt (Velocity change over elapsed time). So I got 12m/s / 36s but what would I do with the 29°? Is the magnitude some kind of cos/sin function? Sorry for sounding dumb, just really lost with the degrees.
     
  5. Oct 11, 2011 #4

    SammyS

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    Acceleration is a vector. You have found the magnitude of the average acceleration. Now find the vector components.
     
  6. Oct 11, 2011 #5
    Yes, you won't be lost when you get the picture:

    Draw a right triangle, with your 29* as the bottom-left acute angle. Your magnitude, or hypotenuse of the triangle, is 12 m/s.

    Using trig, you can find the other legs of the triangle, and those are your components of velocity!

    Once you know both components of velocity, apply your average acceleration formula to each.
     
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