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Help with Homework Problem on Acceleration

  1. Sep 5, 2004 #1
    The land speed record of 13.9 m/s (31 mi/h) for birds is held by the Australian emu. An emu running due south in a straight line at this speed slows down to a speed of 10.5 m/s in 2.7 s.

    What is the direction of the bird's acceleration?

    Assuming that the acceleration remains the same, what is the bird's velocity after an additional 3.9 s has elapsed?
  2. jcsd
  3. Sep 5, 2004 #2
    direction of bird's acceleration: Well obviously it's not due south, otherwise it would be accelerating. Hmm i wonder....

    10.5 = 13.9 + a(2.7)

    a = - (3.4/2.7)m/s^2<------------ what do you think the negative sign signifies?

    for the second part. Just use vf = vi + at
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