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Difference between velocity and speed.

  1. Feb 16, 2010 #1
    A tennis ball of mass 10.0 g bounces vertically on a concrete floor. The ball strikes the floor at 20.0 m s–1 and rebounds at 15.00 m s–1.

    5.
    A. What is the change in speed of the ball as it bounces?

    Δv = v1-v2
    = 20ms-1 - 15ms-1
    Δv = 5ms-1

    B. What is the change in velocity of the ball as it bounces?

    Δv = v1 - v2
    = 20ms-1 – (-15ms-1)
    Δv = 35ms-1


    Does that depict the difference between speed and velocity as speed is a scalar quantity it doesnt have direction therefore when calculating (in this case) is a positive value, but when calculating the change in velocity because it is a vector quanitiy it has a direction ( negative because it's going in the opposite direction as the initial drop) so it has a negative value? Im not sure if this is correct. thank you.
     
  2. jcsd
  3. Feb 17, 2010 #2

    ehild

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    Homework Helper
    Gold Member

    You know it well, velocity is a vector quantity and speed is its magnitude, so a non-negative scalar. Well done!

    ehild
     
  4. Feb 17, 2010 #3
    Awesome, thank you (:
     
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