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Calculating final velocity after a puck is hit

  1. Oct 15, 2016 #1
    1. The problem statement, all variables and given/known data
    Bob passes a 0.220kg puck with an initial velocity of 12m/s [South] to Dave. Dave one-times the puck with a force of 368N [N30E] if Daves stick is in contact with the puck for 0.250s what is the final velocity?

    2. Relevant equations
    i honestly don't know where to start with this one, if you can tell me what i first need to solve for i should be able to go from there

    3. The attempt at a solution
     
    Last edited: Oct 15, 2016
  2. jcsd
  3. Oct 15, 2016 #2

    billy_joule

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    Look in your course notes and/or text book for "Impulse".

    As the question is, it can't be solved, we don't know the initial direction of the puck.
     
  4. Oct 15, 2016 #3
    sorry the initial directon is south
     
  5. Oct 15, 2016 #4

    SammyS

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    Hello kinghunter. Welcome to PF !

    What quantities are you given? What do you need to find ?

    Consider using the Impulse - Momentum Theorem.

    You will need to show an attempt before we can give you any more help.
     
  6. Oct 15, 2016 #5
    i believe the initial velocity when dave hits the puck is 12m/s (carried over from the initial pass), he hits it with a force of 368N [N30E], its in contact with his stick for 0.25s (acceleration period) and the mass of the puck is 0.22kg so what i did is F=ma and a=v/t F=m(vf-vi/t)
    vf=F(t)+vi / m
    =368N(0.25s)+12m/s / 0.22kg
    but then i get an unrealistic number = 472.7m/s
     
  7. Oct 15, 2016 #6

    SammyS

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    For one thing your units are don't work out in several places, partly because you ignore placing parentheses adequately.

    Beyond that: Force, velocity and acceleration are all vector quantities. A force in the east - west direction will only cause acceleration in the east - west direction so only changes the component of velocity in the east - west direction. The component of velocity in the north - south direction will remain unchanged at 12 m/s [south] .
     
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