Question

A satellite is orbiting Earth in an approximately circular path. It completes one revolution each day (86,400 seconds). Its orbital distance is 22,500 kilometers from the Earth's center. What is the satellite's average speed?
a. 5.5 kilometers/second
b. 19.4 kilometers/second
c. 1.64 kilometers/second
d. 384 meters/second

Answer 1

Circular path ... circumference = 2π · Radius

Radius = distance from the Earth's center = 22,500 km

Circumference = 2π · 22,500 km = 141,372 km

Speed = (distance to be covered) / (time to cover the distance)

Speed = (141,372 km) / (86,400 seconds)

Speed = (141,372/86,400) (km/sec)

Speed = 1.64 km/sec

Extra Info:

This problem is a nice exercise in Arithmetic, but you shouldn't take any of it to run with in the real world.

A satellite with a period of 1 day is NOT  22,500 km from the center of the Earth.  It's more like 22,500 MILES from the Earth's SURFACE.

The real number is 22,236 miles above sea level, and 26,199 miles (42,164 km) from the center of the Earth.

To do THAT orbit in 86,400 seconds, the satellite has to zip around at 3.07 km/sec.