A satellite of mass $m$ in a circular orbit of radius $r$ around a planet of mass $M$ has total mechanical energy:
A$+GMm/(2r)$, positive since the satellite is moving
B$+GMm/r$, equal to the kinetic energy alone here
C$-GMm/r$, equal to the gravitational PE only
D$-GMm/(2r)$, half the PE, negative because bound
Answer & Solution
Correct answer: D. $-GMm/(2r)$, half the PE, negative because bound
$K = GMm/(2r)$, $U = -GMm/r$, $E = K+U = -GMm/(2r)$.
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