Pluto has a perihelion of about 50 AU and an aphelion of 30 AU.What is the ratio of the gravitational force at aphelion to the gravitational force at perihelion?
A) 1
B) 5/3
C) 25/9
D) 25/3

Question

Quizplus · Accepted Answer

The gravitational force is proportional to the inverse square of the distance, so the ratio of the gravitational force at aphelion to the gravitational force at perihelion is equal to the square of the ratio of the distances: (30/50)^2 = 9/25. To get the ratio of the gravitational forces, we have to invert this ratio, giving 25/9.

Pluto Has a Perihelion of About 50 AU and an Aphelion