Question #e9b89

1 Answer
Sep 11, 2016

#"0.134 s"#


The idea here is that you can use the speed of light as a conversion factor to help you calculate the time needed for light to travel a distance equal to the circumference of the Earth.

So, the speed of light is given to you in meters per second, #"m/s"#, so the first thing to do here is to convert the distance that light must travel from miles to meters.

#24900 color(red)(cancel(color(black)("mi"))) * overbrace((1.609344color(red)(cancel(color(black)("km"))))/(1color(red)(cancel(color(black)("mi")))))^(color(blue)("miles to kilometers")) * overbrace((10^3"m")/(1color(red)(cancel(color(black)("km")))))^(color(darkgreen)("kilometers to meters")) = 4.0073 * 10^7"m"#

Now set up the speed of light as a conversion factor to find

#4.0073 * 10^7 color(red)(cancel(color(black)("m"))) * "1 s"/(2.998 * 10^8color(red)(cancel(color(black)("m")))) = color(green)(bar(ul(|color(white)(a/a)color(black)("0.134 s")color(white)(a/a)|)))#

The answer must be rounded to three sig figs, the number of sig figs you have for the circumference of the Earth.