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Homework Help: How is the equation given for v_b tangent to it?

  1. Feb 10, 2014 #1
    1. The problem statement, all variables and given/known data

    I'm trying to follow a solved example in the book. I understand everything except one "trivial" (for most of you) analysis of the tangent velocity vector v_b. Because v_b is unknown it is written as its magnitude times the direction it follows constrained in a circular path.

    However, my understanding of v_b written as in the picture followed is not tangent. That is the vector that describes the radius of the path, and not the perpendicular to the radius which will be the instantaneous velocity.

    2. Relevant equations
    Please see attached picture

    3. The attempt at a solution
    how is the equation given for v_b tangent to it? this is the vector describing the radius of the path?

    Thank you

    Attached Files:

    • v_b.jpg
      File size:
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    Last edited by a moderator: May 12, 2014
  2. jcsd
  3. Feb 11, 2014 #2


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    Staff: Mentor

    That right triangle with sides 1 and 1, on the radius of the circular path, indicates that at the current position B is constrained to moving as much to the right as upwards, per unit of time, meaning a velocity vector having equal horiz and vertical components, at the instant represented.
  4. Feb 11, 2014 #3
    Thank you, makes sense now. Wish I'd asked earlier.
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