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Homework Help: Elevator going down and you drop a book

  1. Oct 5, 2008 #1
    1. The problem statement, all variables and given/known data

    While riding on an elevator descending with a constant speed of 3.3 m/s, you accidentally drop a book from under your arm.
    (a) How long does it take for the book to reach the elevator floor, 1.1 m below your arm?
    s
    (b) What is the book's speed (relative to the earth) when it hits the elevator floor?


    3. The attempt at a solution

    4.9m/9.8m/s2=14.7
    squareroot 14.7=3.834=answer a

    1.1m+1/2(13.1)t
    t=7.65
    1.1m/7.65s=.1437=answer b

    both of these answers were wrong. what equations am ia supposed to use?
    how do i start?
     
  2. jcsd
  3. Oct 6, 2008 #2

    Kurdt

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    Staff Emeritus
    Science Advisor
    Gold Member

    For the first part it looks as though you're trying to use the correct equation but I have no idea where you got your numbers from?

    For part b it will just be the speed of the elevator added to the speed you work out from standard kinematic equations.
     
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