Finding net force on an object in a free body diagram

[BlueLine]

Homework Statement

This was an example question done by my teacher but i don't understand how he got the fnet of an object like the yellow part. thanks first time using the forums sorry if i didnt tag this correctly

Homework Equations

The Attempt at a Solution

 

[haruspex]

Can you be more specific about what it is that you do not understand?
For the net force on B, do you understand the preceding line, giving -1.25 x10^-7N? If your question is why that changed into -1x10^-7N, I don't know. Looks like a mistake.
There's no working shown for obtaining the other two net forces. How would you calculate those?

 

[BlueLine]

yeah like how would you solve the question after the gravitational force you get for Fa and Fc. i got lost after the example like i have no idea how he got the fnet of each object. idk how to calculate the fnet... isn't it fnet=ma but what would that do.

 

[haruspex]

yeah like how would you solve the question after the gravitational force you get for Fa and Fc. i got lost after the example like i have no idea how he got the fnet of each object

Each object experiences a pull from each of the other two, as per the inverse square law formula used.
The net force on B will be the difference between the forces exerted by A and C, since those are pulling in opposite directions.
Your teacher has omitted the calculation for the attractive force between A and C. You will need this to find the net forces on A and C.

Can you calculate the attractive force between A and C?
How would you combine this with forces already calculated to find the net force on A?

 

[BlueLine]

how exactly do you calculate the fnet for like the object a and c. the mass is 2.. and is the fa suppose to give me the acceleration?

 

[haruspex]

how exactly do you calculate the fnet for like the object a and c. the mass is 2.. and is the fa suppose to give me the acceleration?

One step at a time. Answer my question about the attractive force between A and C. For this purpose, ignore B.

After that, list the forces acting on A and which way they act. Do they work together or oppose each other?