Question

Light from the sun reaches the earth in 8.3 minutes. the speed of light is 3.0  108 m/s. in kilometers, how far is the earth from the sun?

Answer 1

To determine the distance of the light that has traveled given the time it takes to travel that distance, we need a relation that would relate time with distance. In any case, it would be the speed of the motion or specifically the speed of light that is travelling which is given as 3x10^8 meters per second. So, we simply multiply the time to the speed. Before doing so, we need to remember that the units should be homogeneous. We do as follows:

distance = 3x10^8 m/s ( 8.3 min ) ( 60 s / 1 min ) = 1.494x10^11 m

Since we are asked for the distance to be in kilometers, we convert

distance = 1.494x10^11 m ( 1 km / 1000 m) = 149400000 km