Electric Charge and Force free body diagrams

[Cglez1280]

Homework Statement

A positive charge Q1 = 7.4 μC is located at a point X1 = -2 m, a negative charge Q2 = -9.7 μC is located at a point X2 = 3 m and a positive charge Q3 = 2.1 μC is located at a point X3 = 9 m.

1. Draw free body diagrams for the electric force acting on Q1, Q2 and Q3.
2. Find the magnitude of the force between Q1 and Q2.
3. Find the magnitude of the force between Q1 and Q3.
4. Find the magnitude of the force between Q2 and Q3.
5. Find the magnitude and direction of the net electric force on charge Q1.
6. Find the magnitude and direction of the net electric force on charge Q2.
7. Find the magnitude and direction of the net electric force on charge Q3.
   I've done number 1-4 but still don't understand how to do 5-7. Physics is not my strong point at all.

Q1=7.4*10^-6
Q2=9.8*10^-6
Q3=2.1*10^-6

Homework Equations

Felect=(k*Q1*Q2)/d^2

The Attempt at a Solution

Ok so far I've tried doing things I'll upload a picture but help would be very appreciated. I'm not sure how to calculate the net force

 

[berkeman]

Homework Statement

A positive charge Q1 = 7.4 μC is located at a point X1 = -2 m, a negative charge Q2 = -9.7 μC is located at a point X2 = 3 m and a positive charge Q3 = 2.1 μC is located at a point X3 = 9 m.

1. Draw free body diagrams for the electric force acting on Q1, Q2 and Q3.
2. Find the magnitude of the force between Q1 and Q2.
3. Find the magnitude of the force between Q1 and Q3.
4. Find the magnitude of the force between Q2 and Q3.
5. Find the magnitude and direction of the net electric force on charge Q1.
6. Find the magnitude and direction of the net electric force on charge Q2.
7. Find the magnitude and direction of the net electric force on charge Q3.
   I've done number 1-4 but still don't understand how to do 5-7. Physics is not my strong point at all.

Q1=7.4*10^-6
Q2=9.8*10^-6
Q3=2.1*10^-6

Homework Equations

Felect=(k*Q1*Q2)/d^2

The Attempt at a Solution

Ok so far I've tried doing things I'll upload a picture but help would be very appreciated. I'm not sure how to calculate the net force

It's difficult for me to read the picture of your work, but to find the net force, you add the forces vectorially (magnitude and direction). This is just a 1-d problem, so the forces will either be attractive or repulsive, all along the x-axis.

So to find the net force on Q1 due to the other 2 charges, just add the forces on Q1 from each of the other charges, being careful to get the signs of the magnitudes of the forces right. Take a positive force to be in the positive x direction...