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B Relative velocity of 2 vehicles

  1. Jul 24, 2016 #1
    Two vehicles leave simultaneously from a fork in a road. Vehicle A travels at a velocity of 85 km/h north-east. Vehicle B travels at 104 km/h directly east. Calculate the velocity of vehicle A relative to the velocity of vehicle B.

    Answer (from memorandum): http://imgur.com/a/L0prH

    I do not understand why is Vehicle B traveling west, an explanation on how why this was done would be appreciated!

    aVb = Va - Vb (Velocity of A relative to velocity of B) when do you use this equation?
  2. jcsd
  3. Jul 24, 2016 #2


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    If you are in a car and get overtaken by another car, then relative to the faster car you are going backwards. Not so?
  4. Jul 24, 2016 #3
    Damn it, they took the opposite direction of Vb from the equation aVb = Va - Vb. I should have known better
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