A spacecraft circling the moon at a distance of 384,000 km from the
earth communicates by radio with a person on earth. How much time
elapses between the sending and receiving of a signal?
To calculate the time it takes for a signal to travel from the spacecraft to Earth, we need to consider the speed of the signal. Radio signals travel through space at the speed of light, which is about 300,000 kilometers per second.
The spacecraft is located 384,000 km away from Earth. So, to determine the time it takes for the signal to travel, we divide the distance by the speed of light:
Time = Distance / Speed of light
Time = 384,000 km / 300,000 km/s
Simplifying this calculation, we find:
Time = 1.28 seconds
Therefore, it takes approximately 1.28 seconds for the signal to travel from the spacecraft to Earth.