1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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.

    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


    User Avatar
    Homework Helper

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

  4. Feb 17, 2010 #3
    Awesome, thank you (:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook