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Applications of the Equations of Kinematics for Constant Acceleration

  1. Sep 24, 2009 #1

    jacksonpeeble

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    Gold Member

    1. The problem statement, all variables and given/known data
    A speedboat starts from rest and accelerates at +2.01 m/s2 for 6.55 s. At the end of this time, the boat continues for an additional 6.45 s with an acceleration of +0.518 m/s2. Following this, the boat accelerates at -1.49 m/s2 for 8.80 s.

    Find the total displacement of the boat.

    2. Relevant equations
    http://www.webassign.net/ebooks/cj6/pc/c02/read/main/c02x2_4.htm
    (Hopefully this is public access, if not, the equations can be determined from the work below, assuming that I am using the correct equations.)


    3. The attempt at a solution
    v0=0
    d1=0*6.55+.5*2.01*6.55^2=43.117
    v1=2.01*6.55+.518*6.45=16.5066
    d2=16.5066*6.45+.518*6.45^2=128.018
    v2=16.5066+-1.49*8.8=3.3946
    d3=3.3946*8.8+-1.49*8.8^2=-85.5131

    Any help is, as always, greatly appreciated! Thank you in advance!
     
  2. jcsd
  3. Sep 24, 2009 #2

    Delphi51

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    Homework Helper

    I agree with your first distance (43.117) after time 6.55 s.
    However, at this time I get
    velocity = Vi*t + .5*a*t^2
    = 0 + .5*2.01*6.55^2 = 13.1655 m/s
    This is the initial velocity for the second interval, not 16.5066.
     
  4. Sep 25, 2009 #3

    jacksonpeeble

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    Gold Member

    I see that you changed 6.45 to 6.55. Is this correct, since the problem states "...the boat continues for an additional 6.45 s..."?
     
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