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Vector Question (Velocity & Acceleration)

  1. Sep 20, 2008 #1

    Just need a bit of help with this one. I have done the calcs and gotten the end answer as per the answers at the back of the book, but I am not quite understanding it.

    A particle initially located at the origin has an acceleration of a=3.00j m/s^2 and an initial velocity of Vi=5.00i m/s. Find (a) the vector position and velocity at any time t and (b) the coordinates and speed of the particle at t=2.00sec.

    Okay well i have worked it out and gotten this for the velocity, v = (5.00i + 6.00j)m/s. This is not the end answer. I then had to use Pythagoras and solve the above to get v= 7.81m.s. That is where I'm confused, why did I have to do that, and how is it related?
    Any help appreciated
  2. jcsd
  3. Sep 20, 2008 #2


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    Speed is the magnitude of the velocity. Simple as that really.
  4. Sep 20, 2008 #3
    Angle from i = atan(6.00/5.00)=50.2deg
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