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Homework Help: Hockey Puck

  1. Sep 14, 2007 #1
    A hockey puck slides along a horizontal, smooth icy surface at a constant velocity as shown.

    Draw a free-body diagram for the puck. Which of the following forces are acting on the puck?

    1. weight
    2. friction
    3. force of velocity
    4. force of push
    5. normal force
    6. air drag
    7. acceleration

    Combinations of answers that were wrong


    I've been at this for awhile and can't picture what's going on. Any help or suggestions are appreciated. Thanks for your time.
  2. jcsd
  3. Sep 14, 2007 #2


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    Which do you think are acting on the hockey puck? Never mind the answers that were rejected... what's your feeling as to the right answer?
  4. Sep 14, 2007 #3
    sorry for posting in wrong section

    Well...what i thought was

    -a puck obviously has weight (1)
    -since it's on ice, i think i'm supposed to assume there's no friction (2)
    -it has some kind of velocity, so i believe there is a force of velocity (3)
    -not sure about force of push...i think we're supposed to assume it's just moving on it's own (4)
    -well since there's a weight, which probably means there's a down acceleration due to gravity, there's probably a normal force (5)
    -air drag is probably negligible (6)
    -not sure what kind of acceleration...since it's moving at a constant rate, i know there's no acceleration in that direction, but what about gravity? (7)
  5. Sep 14, 2007 #4


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    yup, 1) is definitely right.

    I agree.

    But velocity isn't a force... there isn't anything I'm aware of such as a force of velocity...

    yup... plus I don't think "force of push" is a real force of any kind... a force is a push or a pull... but a "force of push" sounds strange...

    Yes, there's definitely a normal force.

    I'd say air drag is a force acting on the puck... might be negligible... but they haven't explicitly stated anything about it... so I'd say it is there...

    Yes, there's no acceleration... the normal forces balances gravity... but more importantly acceleration isn't a force....
  6. Sep 15, 2007 #5
    Even if the puck is on ice, I wouldn't automatically assume no friction. Otherwise hockey pucks could be tapped slightly and potentially go across entire arenas. I'd say include at least a small friction force opposing motion.
  7. Sep 28, 2007 #6

    There will be only Weight and Net Force acting on the puck. AE would be your answer.
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