An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be
A)zero.
B)40 N.
C)120 N.
D)360 N.
E)1080 N.

Question

Quizplus · Accepted Answer

The force exerted by the asteroid on the spacecraft depends on the mass and distance between them. As the spacecraft moves to a position three times as far from the center of the asteroid, the distance between them increases by 3 times. According to the inverse square law of gravitation, the force of gravity decreases by a factor of 3^2 = 9. Therefore, the force will be (360 N)/9 = 40 N. So, the best choice is B.

An Asteroid Exerts a 360-N Gravitational Force on a Nearby