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Homework Help: Vector and acceleration problem

  1. Sep 23, 2007 #1
    1. The problem statement, all variables and given/known data
    A bird takes 8.5s to fly from position A{ V = 4.4 m/s [31° S of E]} to position B{ v = 7.8 m/s [25° N of E]}. Determine the average acceleration.


    2. Relevant equations
    [tex]a_{ave} = \Delta V / \Delta t[/tex]
    [tex]\Delta Vx = Vbx + (-Vax)[/tex]
    [tex]\Delta Vy = Vby + (-Vay)[/tex]

    3. The attempt at a solution
    [tex]\Delta Vx = Vbx + (-Vax)[/tex]
    = [tex]Vb \sin \Theta + (-Va \cos \beta)[/tex]
    = [tex]7.8 m/s (\sin31) - 4.4 m/s(\cos25)[/tex]
    = 0.0295 m/s

    [tex]\Delta Vy = Vby + (-Vax)[/tex]
    = [tex] Vb \cos \Theta + (-Va \sin \beta)[/tex]
    = [tex] 7.8 m/s (\cos31) + 4.4 m/s (\sin25)[/tex]
    = 8.545 m/s

    [tex]\mid \Delta V\mid^2 = \mid \Delta Vx \mid^2 + \mid \Delta Vy \mid^2[/tex]
    = [tex](0.0295)^2 + (8.545)^2[/tex]
    = 8.545 m/s

    [tex]a_{ave} = \Delta V / \Delta t[/tex]
    = (8.545m/s) / (8.5s)
    = 1.005

    This is how far i've got and I checked the answer with my textbook it says that the answer should be 0.76 m/s ^2.

    Can someone help please?
     
    Last edited: Sep 23, 2007
  2. jcsd
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