Question

The gravitational force of a star on an orbiting planet 1 is f1. planet 2, which is four times as massive as planet 1 and orbits at three times larger distance from the star, experiences gravitational force f2

Answer 1

Answer: F=GMm/r^2 where G is the newtonian grav cst, M the mass of the star, m the mass of the planet, and r the planet-star distance F1=GMm1/r1^2 F2=GMm2/r^2 F2/F1 = [GMm2/r2^2]/[GMm1/r1^2] F2/F1=(m2/m1)(r1/r2)^2 = (2)(1/2)^2 = 1/2 because m2/m1=2 and r2/r1=2