# 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?

1
dari shi2kink1ishaven

## Jawapan

2016-03-17T11:10:40+08:00
Well, speed is always relative to some reference, and you haven't
specified the reference.  Also, you haven't specified the "tilt" of the
satellite's orbit relative to the Earth's equator.

So I'm going to pick the ones I like for both items:

-- For the satellite's average speed, I choose the reference
to be the center of the little satellite-TV dish on the corner of
my neighbor's garage roof.

-- For the satellite's orbital inclination, I choose zero.  That is,
the satellite's orbit is directly over Earth's equator.

If you'll allow me those two assumptions, then your bird is
a communications satellite, located at the magic latitude
and distance from Earth where its orbital revolution matches
the Earth's rotation.  Viewed from anywhere on Earth, the
satellite's average speed is zero, and it appears to hang
motionless in the sky.