試題詳解

複選題
1. Newton's law of gravitation states that there exists an attractive force between the planet and the sun of masses m and M, respectively. The magnitude of the force is written as F = GmM /r², where r is the distance of the planet from the sun, which is called the central force. The orbital motion of a particle under a central force is always
(A)unbounded
(B) bounded
(C) confined to a plane
(D) None of these.