1. Not finding help here? Sign up for a free 30min 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!

Finding Distance -- Hockey Puck Velocity

  1. May 10, 2017 #1
    1. The problem statement, all variables and given/known data
    An ice hockey puck leaves a hockey stick with a velocity of 45 m/s, how far will it travel in 3.0 seconds?


    2. Relevant equations
    D = v/t or

    ## \Delta \vec d= \frac 1 2 \vec a \Delta t^2##

    with ## \vec a = v_2 / \Delta t##

    3. The attempt at a solution

    D = v/t
    = 45 m/s / 3 = 135 meters

    or ##0.5 (15 m/s^2) (3)^2## = 67.5 meters

    Which one is it, and more importantly... how do I tell the difference on when to use each formula?

    Thank you
     
  2. jcsd
  3. May 10, 2017 #2

    kuruman

    User Avatar
    Homework Helper
    Gold Member

  4. May 10, 2017 #3
    Since no friction is mentioned, I believe for this problem you should assume there is no friction, which means the velocity is constant. In other words, a = 0.
     
  5. May 10, 2017 #4
    Thank you both very much. Very helpful.
     
  6. May 10, 2017 #5
    Actually a follow up question to this adds friction. The puck is hit with a force of 15.3 N and the friction slowing it down is 0.75 N.
    Same time (3.0 s) same velocity (45 m/s)

    So a = f/m then plug that into the second formula mentioned above?
     
  7. May 10, 2017 #6

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Those equations are not quite right. It is ##\Delta d= v\Delta t+ \frac 1 2 a \Delta t^2## and ##a =\Delta v/\Delta t##.
    You are not told the puck stops in 3 seconds. If you assume it keeps going at v then Δv=0 and a =0, so you end up with the same equation as d=vt.
     
  8. May 10, 2017 #7
    Extremely helpful. Thank you
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Finding Distance -- Hockey Puck Velocity
Loading...