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Homework Help: Relative vectors - how do you determine?

  1. Mar 25, 2010 #1
    1. The problem statement

    I find it sometimes difficult to come up with the equation relevant to the question. If any one has any tips, your help is appreciated.

    2. Relevant example

    For example:

    A passenger climbs aboard a northbound bus and walks toward the back at a rate of 1.8m/s. The bus starts off up the street at 9.2m/s. What velocity will the passenger appear to be walking relative to:

    A) a person who is walking 2.1 m/s south along the sidewalk
    B) a person who is walking 2.1 m/s north along the sidewalk

    3. The attempt at a solution

    Let p = passenger in the bus
    b = Bus
    g = guy who is walking

    My attempt: a) Vpg = Vpb + Vbg is this correct? why or why not? thanks.
  2. jcsd
  3. Mar 25, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Trooper100! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    Yes, that's correct, because you've put the letters in the right order … pg = pb + bg. :smile:

    (For example , if you wanted to know Vpb,

    you would write Vpb = Vpg + Vgb = Vpg - Vbg :wink:)
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