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Fundamental of Physics 10th Edition Problem 52

  1. Aug 31, 2014 #1
    1. The problem statement, all variables and given/known data

    A bolt is dropped from a bridge under construction, falling 83 m to the valley below the bridge. (a) How much time does it take to pass through the last 20 % of its fall? What is its speed (b) when it begins that last 20 % of its fall and (c) just before it reaches the ground?

    2. Relevant equations



    3. The attempt at a solution

    For part (a) I got the correct answer of .436 seconds by doing 83/4.9=16.94, sqrt16.94=4.12
    83 x .20 = 16.6
    83-16.6=66.4
    66.4/4.9=13.55
    sqrt13.55=3.68
    4.12-3.68=.436

    That answer was correct but I need parts (b) and (c)
     
  2. jcsd
  3. Aug 31, 2014 #2

    SteamKing

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    Knowing the time something is falling under gravity, how do you calculate the velocity? You've learned one equation of kinematics; there's a couple more equations you need to learn as well.
     
  4. Aug 31, 2014 #3
    I'm sorry but that really doesn't help my understanding of how to do it.
     
  5. Aug 31, 2014 #4

    SteamKing

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    It means there are some other equations that you need to learn:

    http://mathematicsi.com/deriving-suvat-equations-motion/ [Broken]
     
    Last edited by a moderator: May 6, 2017
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