An object weighs 432 N on the surface of the earth. The earth has radius R . If the object is raised to a height of 3 R above the earth's surface, what is its weight?
A) 108 N
B) 27.0 N
C) 48.0 N
D) 144 N
E) 305 N

Question

An object weighs  432 N on the surface of the earth. The earth has radius  R . If the object is raised to a height of  3 R  above the earth's surface, what is its weight?
A)  108 N
B)  27.0 N
C)  48.0 N
D)  144 N
E)  305 N

Quizplus · Accepted Answer

The gravitational force decreases with the square of the distance from the center of the Earth. At a height of 3R, the distance from the center is 4R. The weight is then (1/4^2) of the original weight, which is 432 N / 16 = 27 N.

An Object Weighs 432 N on the Surface of the Earth