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Homework Help: Velocity and vector calculus

  1. Jun 14, 2010 #1
    1. The problem statement, all variables and given/known data

    An object moves according to this : r(t)= (1+t^2)i + (1-t)j + (t+t^3)k

    How fast does it moves far from O(0,0) for t=1?

    Is this velocity the same with the object's velocity?

    3. The attempt at a solution

    I cant understand the second part
  2. jcsd
  3. Jun 14, 2010 #2


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    I can't seem to understand the second part either.

    By the first one, do you mean, what its velocity is at t = 1, or what its position is? What is the relation between the two?
  4. Jun 14, 2010 #3
    i mean the velocity for t=1 which is r'(1)= 2i-j+4k
    The r(t) in my previous post is the position vector from the start (0,0)

    is the any reason for not the r'(t) or r'(1) to be the objects velocity?
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