Speed of waves and time delay question

1. Oct 20, 2014

kirsten_2009

1. The problem statement, all variables and given/known data

What is the time delay for a television signal that is sent via satellite? Communications satellites orbit above the equator in circles of radius 36,000 km (6 times larger than Earth’s radius!).

Not sure if my answer is correct...

2. Relevant equations

time=distance/speed

3. The attempt at a solution

Not sure how satellite signals work but I assume that they operate on the surface of the Earth and that the signal travels to the Earth’s surface and back to the satellite…so the actual distance would be 36,000 km – 6,000 km (the distance from the center of the Earth to the surface) = 30,000 km x 2 (round trip) = 60,000 km.

time = distance / speed = 60,000 km / 3x10⁵ km/sec = 0.2 sec

2. Oct 20, 2014

marcusl

Your method is sound, but I'd double-check the orbit. 36,000 km is usually quoted as the orbit altitude, making 42,000 km radius from the Earth's center.