Units Dimensions and Conversions

One light-year is the distance that light travels in exactly one year.
If the speed of light is 6.7 x 10⁸ mph, convert light-years to:
a. miles
b. meters

(a) 5.9x10¹² mi   (b) 9.4x10¹⁵ m

Solution Steps:

We need to change 6.7x10⁸ miles in one hour to ?? miles in one year and then to ?? meters in one year. We'll need some conversion equations:

1 mi = 1.61x10³m

1 day = 24 hr

1 yr = 365 days

Notice that the last two equations can be combined to give:

1 yr = 8760 hr

Here are the two calculations:

We'll state the answers to two sig figs, since the speed of light was given that way.

Another problem like this one.

Developed by

Shodor
in cooperation with the Department of Chemistry,
The University of North Carolina at Chapel Hill