The Earth has a radius of about 6,000 km. How long would it take for an object traveling at the speed of light to circle the earth? (Recall that the speed of light is 300,000 km/s)
A)1/50 of a second (0.02s)
B)1/300,000 of a second (0.0000033 s)
C)1/ 6000 of a second (0.00015 s)
D)1/2 of a second (0.5 s)

Question

Quizplus · Accepted Answer

The circumference of the Earth is 2πr, where r is the radius (6,000 km). This gives approximately 37,700 km. At the speed of light (300,000 km/s), it would take 37,700 km / 300,000 km/s = 0.1257 seconds to circle the Earth, which is closest to 1/50 of a second (0.02s).

The Earth Has a Radius of About 6,000 Km