Fundamental of Physics 10th Edition Problem 52

  • #1

Homework Statement



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?

Homework Equations





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)
 

Answers and Replies

  • #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.
 
  • #3
I'm sorry but that really doesn't help my understanding of how to do it.
 
  • #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]
 
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