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Quick simple vector question

  1. Oct 13, 2014 #1
    Very simple question but I am confused... I am asked to find Particle A's speed with respect to Particle B. What does this mean?

    I am given:
    Particle A: (15i - 10j) or 18.03 m/s
    Particle B: (5i + 15j) or 15.81 m/s

    I just don't understand what I'm being asked to find and how to go about solving for it...
  2. jcsd
  3. Oct 13, 2014 #2


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    Staff: Mentor

    Welcome to the PF.

    To get the speed of one "with respect to the other", just do a vector subtraction of their two vector velocities. :-)
  4. Oct 13, 2014 #3
    So if I'm trying to find Particle A in terms of B would I do A - B or B - A?
  5. Oct 13, 2014 #4


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    Science Advisor

    It doesn't matter. Speed is absolute value.
  6. Oct 13, 2014 #5
    Oh that's true, silly me. Thankyou!
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