The orbital speed of a satellite in a circular orbit of radius r around a planet of mass M is:
Av = √(G M / r)
Bv = √(2 G M / r)
Cv = √(G M r)
Dv = √(G M / r³)
Answer & Solution
Correct answer: A. v = √(G M / r)
1. For a circular orbit, gravity provides the centripetal force: G M m / r² = m v² / r.
2. Cancel m and rearrange: v² = G M / r.
3. v = √(G M / r).
4. Distractor √(2 G M / r) is the escape speed from that radius — a common confusion.
_Source: NCERT Class 11 Physics Ch 7 "Gravitation", §7.9 Earth Satellites, p. 137_
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