Calculating Gravitational Force on Multiple Spheres - Physics Homework Problem

[saintv]

Homework Statement

Question: Four 8.0 kg spheres are located at the corners of a square of side 0.50m. Calculate the magnitude and direction of the gravitational force on one sphere due to the other three.

Answer from Back of Textbook: 3.3 x10^-8 N toward diagonally opposite sphere

Homework Equations

F = (Gm1m2)/r^2

m1 = mass1
m2 = mass2
G = constant 6.67 x 10^-11
r = radius

g = (Gm)/r^2

g = acceleration due to gravity.

I believe that these are the only two applicable to this question.

The Attempt at a Solution

Er, its kinda hard to attempt it if you don't have a clue what's going on. If someone could just push me in the right direction and give me a hint as to where to start, that would be awesome!

 

[srmeier]

have you were heard of the term "superposition?" And if so, what does it mean to you?

(just asking, not being sarcastic ^^)

 

[saintv]

have you were heard of the term "superposition?" And if so, what does it mean to you?

(just asking, not being sarcastic ^^)

No, I actually haven't.

 

[srmeier]

in essence, it means that we can calculate the gravitational force due to each of the three spheres on the fourth and sum them together to find the net force acting on the fourth sphere.

So in your problem sphere #1 experiences a pulling force from sphere #2, #3, & #4.

net force acting on sphere #1 = force caused by #2 + force caused by #3 + force caused by #4

Make sense?
(note: the formula above gives the magnitude of the net force not the direction.)