Problema Solution
An object is 7.7 x 107 miles from Earth. How long (in seconds) does it take for light from this object to reach the earth if it travels at 3x108 m/s?
Answer provided by our tutors
Let
d = 7.7 * 10^7 mi the distance
c = 3*10^8 m/s = 3*0.000621371*10^8 mi/s (since 1 m = 0.000621371 mi)
t = the time in seconds
since speed = distance/time follows time = distance/speed that is:
t = d/c
t = 7.7 * 10^7/(3*0.000621371*10^8)
........
........
t = 413.07 s
It takes 413 seconds for the light to reach the Earth.