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An object falls a distance s given as s=16t^2. find instanteneous rat

  1. Dec 13, 2013 #1
    An object falls a distance s given as s=16t^2.

    WHAT is the change of in distance, pr distance travelled, from t=3 and t=5?
    What is the average rate of change of distance compared to time inthat time interval?
    What is the average speed in that time interval?

    Please help. I did values between t=4 and t=4.1 and instantaneous speed was approaching 128.
    That was the example in the book.

    Yet when i tried to do values between 3 and 3.1. my answer is way off. WHat is the problem asking me for?

    ie when t=3; s=16x9=144
    when t=3.1; s=16x9.61=153.76 then, 153.76-144=9.76/.1= 97.6

    what am I doing wrong?
  2. jcsd
  3. Dec 13, 2013 #2


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    Hi TitoSmooth! :smile:
    You're only doing the speed at 3.

    The question doesn't ask for that, it asks for the average for the whole time between 3 and 5. :wink:
  4. Dec 13, 2013 #3


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    How far had it fallen between t=0 and t= 3? How far had it fallen between t= 0 and t= 5?
    So how far did it fall between t= 3 and

    Average rate of change is distance traveled divided by time

    "Speed" is "rate of change of distance"!

    This problem does not ask for instantaneous speed. It asks for average speed.

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