Two comets are found at the same distance from the Sun. However, one comet is three times as massive as the other. According to Newton's Universal Law of Gravitation the force of gravity exerted by the Sun on the more massive comet is
A) one-ninth the size of the force exerted on the less massive comet
B) one-third the size of the force exerted on the less massive comet
C) the same size as the force exerted on the less massive comet
D) three times as large as the force exerted on the less massive comet

Question

Quizplus · Accepted Answer

According to Newton's Universal Law of Gravitation, the force of gravity between two objects is directly proportional to their masses and inversely proportional to the square of their distance. Since the two comets are at the same distance from the Sun, the force of gravity between each comet and the Sun is directly proportional to the mass of each comet. Therefore, the more massive comet exerts a force on the Sun that is three times greater than the force exerted by the less massive comet. However, the force of gravity exerted by the Sun on each comet is the same, since it depends only on the mass of the Sun and the distance between each comet and the Sun. Therefore, the answer is D, three times as large as the force exerted on the less massive comet.

Two Comets Are Found at the Same Distance from the Sun