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Time and Velocity (Big Four?)

  1. Dec 9, 2011 #1
    A chipmunk drops an acorn from a branch 6.0 m above the ground.
    a) How long is it in the air?
    b)How fast is it going when it hits the ground?


    I decided my given was
    a=9.8m/s2
    d= 6.0 m
    vi= 0 m/s

    So I used the distance formula (d=vi+1/2*a*t2) and solved for time. I got about 1.1 s.
    For the next part I used vf=vi*t+a*t and solved.

    I got
    a)1.1 seconds
    b) 10.78 m/s

    Is this correct?
     
  2. jcsd
  3. Dec 9, 2011 #2

    PeterO

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    Homework Helper

    Method good, but the fact you rounded off the time before calculating velocity is not desirable. Without rounding the vel calculates to 10.84

    Given that orignal data was to 2 figures only, the velocity should be rounded to 2 figures, which will give 11 in both cases. You even get the same result if you stretch to 3 figures - 10.8, but if you quote 4 figures; 10.78 is incorrect.
     
  4. Dec 9, 2011 #3
    Thank you so much! Highly appreciated.:)
     
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