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Homework Help: Question on considering final velocity

  1. Jan 18, 2013 #1
    1. The problem statement, all variables and given/known data

    bolt comes loose underneath an elevator that is moving upward at a speed of 6.0 m/s and reaches the bottom in 3.0s . find how high above the bottom of the shaft it came loose and the speed of the bolt when it hits the bottom.

    i figured out the problem but my question is why dont you consider the final velocity as 0 because when the bolt is on the bottom of the shaft there is no velocity? this is what i first tried to do when attempting to find the initial velocity but that is wrong....so i just wanted to know why i cant put v final as 0.

    2. Relevant equations


    3. The attempt at a solution
  2. jcsd
  3. Jan 18, 2013 #2

    Doc Al

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    Staff: Mentor

    You are considering the motion of the bolt under the influence of gravity alone. So the 'final' velocity in your kinematic analysis should be the speed of the bolt just before it hits the floor of the elevator.

    After it hits the floor of the elevator, other forces come into play.
  4. Jan 18, 2013 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Because the velocity of the bolt does not go to zero until after it has struck the bottom of the shaft.
  5. Jan 21, 2013 #4
    thank you!
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