A new solar system with two planets of equal mass - Planet X and Planet Y - is discovered. Planet X is closest to the sun.

What is the sun's gravitational pull on Planet Y as compared with Planet X?

Question

A new solar system with two planets of equal mass - Planet X and Planet Y - is discovered. Planet X is closest to the sun. 

 

What is the sun's gravitational pull on Planet Y as compared with Planet X?

anonymous · Answer

A.
	The sun's gravitational pull on Planet Y is equal to its gravitational pull on Planet X because distance does not affect the sun's gravity.
	
 
B.
	Because Planet Y is farther from the sun, the sun's gravitational pull on Planet Y is more than the sun's gravitational pull on Planet X.
	
 
C.
	Because Planet Y is farther from the sun, the sun's gravitational pull on Planet Y is less than the sun's gravitational pull on Planet X.
	
 
D.
	The sun's gravity repels Planet Y with more force than it repels Planet X, which is why Planet Y is farther away.

anonymous · Answer

The force of gravity is given by:$$F=G \frac{ m _{1} m _{2}}{ r ^{2} }$$where F is the force of gravity; G is the gravitational constant; m1 is mass 1; m2 is mass 2; and r is the distance between those two masses.  Looking at that equation, what happens to F as r increases?

anonymous · Answer

um thats a little confusing I never learned that formula

anonymous · Answer

For this problem, G, m1, and m2 don't change.  So you can rewrite the formula, in this case, as:$$F=\frac{ K }{ r ^{2} }$$where K is a constant.  Now if r is 1 we get: $$F=\frac{ K }{ 1^{2} }$$If r=2 we get:$$F=\frac{ K }{ 2^{2} }$$And if r=3, we get:$$F=\frac{ K }{ 3^{2} }.$$So, is F getting bigger or smaller as r gets larger?