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How fast is the shell moving when it hits the rocks?

  1. Jan 24, 2005 #1
    Seagulls are often observed dropping clams and other shellfish from a height to the rocks below, as a means of opening the shells. If a seagull drops a shell from rest at a height of 14m, how fast is the shell moving when it hits the rocks?

    X= 1/2 gt^t

    i got 1.68945 secs do I round off to 1.7 or 1.69?
     
  2. jcsd
  3. Jan 24, 2005 #2

    quasar987

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    That really irrelevant physically. What you have to do is ask your teacher how many decimals he wants you to round up to. In my days, it was 2 decimals. So 1.69 would have been the answer that wouldt have avoided me to lose .25 points in an exam.
     
    Last edited: Jan 25, 2005
  4. Jan 25, 2005 #3
    Are significant digits not concerned here rather than decimal places? My answer on an exam would be 1.7, because the original datum has two significant digits.
     
  5. Jan 25, 2005 #4

    quasar987

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    Like I said, it's his teacher's choice. We didn't care about significant digits, it was 2 decimals, that's all.
     
  6. Jan 25, 2005 #5

    HallsofIvy

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    Then your teacher was being sloppy. There is no point in pretending that your answer is more accurate than the data you were given.

    I will agree that it is a good idea to check with your teacher to see how precise he/she wants you to be. It is your teacher that is giving you your grade, not quasar986 or myself!
     
  7. Jan 25, 2005 #6
    absolutely!

    i think the point to be discussed with the teacher is exactly that: does the teacher have a "preferred" number of digits for rounding, accuracy, etc., or do they really want you to get the idea that your answer is only as accurate as the accuracy of the least accurate number in your calculations or measurements!

    i believe that is the best lesson to take away from this question......
    +af
    :smile:
     
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