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Find the angle using components

  1. Sep 13, 2009 #1

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

    A particle moves in the xy plane with constant acceleration. At time t = 0 s, the position vector for the particle is d=68m(x-hat)+96m(y-hat). The acceleration is given by the vector a=65m/s^2(x-hat)+50m/s^2(y-hat). The velocity vector at time t = 0 s is v=77m/s(x-hat)−58m/s(y-hat).

    Find the magnitude of the velocity vector at time t= 5.1 s. (This part I have solved)

    Vf= 45.4 m/s (with x-component 40.85m/s (x-hat) and y-component 19.7m/s (y-hat).

    What is the angle between the velocity vector and the positive x-axis at time t = 5.1 s? (This is my question)

    2. Relevant equations

    arctan(Vy/Vx) = Theta

    3. The attempt at a solution

    Arctan(19.7/40.85)= 25.75 degrees = Theta

    I have tried the angle I found as theta, theta+180 degrees, 180 degrees - theta.

    I thought this problem was really simple, but for some reason I just can't seem to get it right no matter how many times I look at similar problems.
    Last edited: Sep 13, 2009
  2. jcsd
  3. Sep 15, 2009 #2


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    I hate it when that happens.

    Welcome to PF! :smile:
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