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Homework Help: Significant Figures rule help

  1. Jan 28, 2007 #1
    1. The problem statement, all variables and given/known data
    This is probably a ridiculous question for many of you, but I want to make sure I have understood the significant figures rule. I am putting this in the physics section because it's from my physics book.

    3. The attempt at a solution

    a) Seconds in 1.00 year:
    1 year x 365 x 24 x 60 x 60 = 31,536,000 seconds in a year = 3.15 x10^7 sec/y.

    b) Nanoseconds in 1.00 year:
    (Seconds in a year) x (nanoseconds in a second)= 31,536,000x1x10^-9 = 0.031536 = 3.15 x 10^-2 nanoseconds in a year.

    c) Years in 1.00 seconds:
    1.00seconds x (1 minute/60 seconds) x (1 hour / 60 minutes) x (1 day/ 24 hours) x (1 year/365 days) = 3.17x 10^-8 year in 1.00 seconds.

    Would this be correct?

    Thank you so much.
  2. jcsd
  3. Jan 28, 2007 #2
    a) and c) looks good.
    b) How many nano seconds is there in 1 second?
    Is there really 3.15 x 10^(-2) nanosseconds i a year :rolleyes:?
  4. Jan 28, 2007 #3
    Would it be 31536000 x 1second/(1x10^-9)=3.15 x 10^16 ?

    Thanks for pointing this out and for your help!
  5. Jan 28, 2007 #4
    Yea, that's correct.
  6. Jan 28, 2007 #5
    If you want to be strict with sig figs, your answer should only have 2 because youre multiplying by 24 and 60 in your work. However, conversion factors like that can conveniently be extended to 24.0 hours/1.00 day and 60.0 minutes/1.00 hour. Its no big deal for conversions, but if a measurement has 2 sig figs, your answer is only accurate to 2 sig figs
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