9-76. Most telecommunications satellites are in geosynchronous orbits above the earth, that is, they have periods of 24 h. As a result, since the earth turns on its axis once in 24 h and each satellite goes around the earth once in 24 h, any individual satellite stays positioned above a particular point on the earth. (a) How far above the earth's surface must a geosynchronous satellite be? The earth's mass and average radius are 5.98X10²⁴ kg and 6368 km. (b) What is the satellite's speed?

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The satellite remains in orbit because:
(A)   It is in a weightless environment.
(B)   There is a centripetal force provided by gravity.
(C)   There is a foreward force from the launch propelling it around in the orbit.