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Math Help - Distance of 1 Light-year (in miles)

  1. #1
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    Distance of 1 Light-year (in miles)

    One light-year is the distance light travels in a 365-day year. The speed of light is about 186,282.4 miles per second. How long is a 2 light-year period (in miles). Express your answer in scientific notation.

    MY WORK:

    1 mile = 5280 feet

    1 hour = 60 minutes = 3600 seconds

    1 day = 24 hours * 3600 seconds = 86,400 seconds

    Then 86,400 seconds * 365 days = 31,536,000 seconds

    I don't know how to use this information to answer the math question.
    Last edited by fdrhs1984; September 13th 2010 at 09:06 AM. Reason: Make Correction
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  2. #2
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    e^(i*pi)'s Avatar
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    You have miles per second and seconds.

    \dfrac{(miles)}{(second)} and (second)

    To get an answer in miles you need to eliminate the seconds unit. What do you know about fractions?
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  3. #3
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by fdrhs1984 View Post
    One light-year is the distance light travels in a 365-day year. The speed of light is about 186,282.4 miles per second. How long is 1 light-year (in miles). Express your answer in scientific notation.

    MY WORK:

    1 mile = 5280 feet

    1 hour = 60 minutes = 3600 seconds

    1 day = 24 hours * 3600 seconds = 86,400 seconds

    Then 86,400 seconds * 365 days = 31,536,000 seconds

    I don't know how to use this information to answer the math question.
    lol ....

    number of miles per second multiply with number of seconds

     186,282.4(speed \;  of light \;   in \;   miles  \; per \;   second  )  \cdot 31,536,000 (seconds  \;  in  \;   one  \; year ) = 5, 874, 601, 766, 400 (miles)

    or
     5.87 \cdot 10^{12}  (miles)
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  4. #4
    MHF Contributor undefined's Avatar
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    Quote Originally Posted by fdrhs1984 View Post
    One light-year is the distance light travels in a 365-day year.
    Might interest you to know that it should actually be 365.25 days.
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  5. #5
    Senior Member yeKciM's Avatar
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    you have number of second per year (365.25 or 365 depending of precision that you need)

    and you have speed of light in miles per second ....

    than for one ore two or ... any number of years ... ( you just need number of seconds ) and multiply it with that speed of light .... and you will get in miles distance that light goes for that time
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  6. #6
    Senior Member Educated's Avatar
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    velocity * time = distance
    m/s \times s = m

    You have the velocity and time, so just multiply them together to solve for the distance travelled.

    So in 2 years, light travels 1.17492 \times 10^{13}miles (assuming it is in a vacuum, and there are 365 days in a year)

    Or to be more accurate, assuming there are 365.25 days in a year, light travels 1.17573 \times 10^{13}miles
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