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Homework Help: PLease check my Speed answer

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

    A man standing on the sidewalk throws a set of keys vertically upward to his
    wife in the window of their apartment 4.0 m above. The wife catches the keys
    1.5 s later. (a) With what initial speed were the keys thrown? (b) What is the
    velocity of the keys just before they were caught? (c) Draw a diagram showing
    the trajectory of the keys.

    3. The attempt at a solution

    d= 4.0 m
    Δt= 1.5 s
    g= -9.8 m/s^2

    Δd= ViΔt+1/2aΔt

    -ViΔt= 1/2 at2-Δd

    -Vi= 1/2 at2- Δd /Δt

    -Vi= -10.016 m/s

    ANSWER FOR A ->>Vi= 10.016 m/s

    b) Vf= Vi+at

    Vf= (110.016 m/s)-(9.8)(1.5)= (-4.684m/s)

    ANSWER FOR B >> -4.684 m/s
  2. jcsd
  3. Dec 5, 2008 #2


    User Avatar
    Homework Helper

    Hi cbrowne,

    Your answers look right to me.
  4. Dec 5, 2008 #3


    User Avatar
    Homework Helper

    Your answers are correct.
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