An object at the surface of Earth (at a distance R from the center of Earth)weighs 90 N.Its weight at a distance 3R from the center of Earth is:
A)10 N
B)30 N
C)90 N
D)270 N
E)810 N

Question

Quizplus · Accepted Answer

The gravitational force (and thus weight) is inversely proportional to the square of the distance from the center of the Earth. If the distance triples (from R to 3R), the weight decreases by a factor of 3^2 = 9. Therefore, 90 N / 9 = 10 N.

An Object at the Surface of Earth (At a Distance