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Dimensional Analysis of a lens

  1. Sep 5, 2008 #1
    Hello everybody, I am taking a basic undergrad General Chemistry I course and am just having a little trouble brushing myself up on dimensional analysis (or factor label). This is the problem.

    The area of a telescope lens is 7903 mm2. (a) What is the area in square feet? (b) If it takes a technician 45 sec to polish 135 mm2, how long does it take her to polish the entire lens?

    I am just not so sure how to get from millimeters squared to square feet. If anyone can help me out I'd really appreciate it. Thank you.
     
  2. jcsd
  3. Sep 5, 2008 #2

    symbolipoint

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    Part (a) --- Note carefully, you have millimeters*millimeters, and you want to convert to feet*feet.
    1000 millimeters = 1 meter
    1 meter = 100 centimeters
    2.54 inches = 1 centimeter
    12 inches = 1 foot.
     
  4. Sep 5, 2008 #3
    Oh I see, so do I simply treat it as 1000 millimeters * 1000 millimeters and so on with the conversions?
     
  5. Sep 6, 2008 #4

    symbolipoint

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    Each units equivalence relation is used as a ratio in your conversion calculation. You do not start with 1000 mm * 1000 mm [excuse the abbreviations], but you are starting with 7903 mm*mm [or in lengthy expressiveness, 7903 * millimeters*millimeters]. Use the unit equivalency relationships from there.
     
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