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Math Help - Unknown time to work out speed

  1. #1
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    Unknown time to work out speed

    Particle A has velocity (8i - 3j)ms^-1 and particle B has velocity (15i - 8j)ms^-1.

    A) Find the speed of B
    B)Find the velocity of B relative to A
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  2. #2
    Super Member Aryth's Avatar
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    A) Speed is just the magnitude of the velocity vector:

    So, if particle B has velocity (15i - 8j) ms^{-1}, the speed is:

    v = \sqrt{15^2 - 8^2}

    v = \sqrt{225 - 64}

    v = \sqrt{161}

    v = 12.7 ms^{-1}

    B) Relative velocity is just the difference of the velocities, so the velocity of B relative to A is:

    (15i - 8j) - (8i - 3j) = (7i - 5j) ms^{-1}
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    thanks
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