Question

What is the vector sum of all the gravitational forces acting on the system of four masses shown in the figure below? (Take x = 18.44 m.) see figure at: http://www.webassign.net/colfunphys1/6-p-040-alt.gif

Answer 1

Not sure what does "vector sum" means..

Answer 2

That is what I did not understand, I thought since there is not external force all the internal forces should add to zero.

Answer 3

But gravitational force changes with height.

Answer 4

If I apply law of gravitation and calculate net gravitational force acting on each mass, would it work?

Answer 5

im not sure what happens over here..
like particle A goes to B then to C and so on?
idk

Answer 6

To which body are we referring to? The vector sum of the forces is different for each one.

Answer 7

I just asked my cousin to put it in 0 for the answer and it worked!

Answer 8

Yeah. If we are considering all four masses as the system then there is no external particle (no particle E) pulling on them so no force.

Answer 9

That is my understanding of what the question is asking. But that seems way too trite. They probably want you to calculate the gravitational force on each particle A,B,C,D separately and then sum these force vectors.

Answer 10

I guess he doesn't care since the answer "worked". lol

Answer 11

I care. As I said my initial guess was zero since there are no external forces.

Answer 12

Thanks for your help guys.

Answer 13

That just seems too simple but maybe that is what they are going for.

Answer 14

np :)