Four charged particles at the corners of a square

[mustang]

problem 12.
Four charged particles are placed so that each particle is at the corner of a square. The sides of the square are 13 cm. The charge at the upper left corner 3.6 uC, the charge at upper right corner -6.5 uC, the charge at lower left corner, and the charge at the lower right corner is -9.1 uC.
What is the magnitude of the net electric force on the 3.6 uC charge? Answer in N.
Note: What formula(s) should I use?

 

[Doc Al]

Use Coulomb's law to find the force exerted by each of the three charges on the 3.6 uC charge. Then add these forces, remembering that they are vectors.

(Why did you start a new thread?)

 

[mustang]

Answer

Is the answer 16.6607574, by adding 4.213065089 with 12.44769231?

 

[Doc Al]

I have no idea where you got those numbers. (Show your work.) Start by finding the three forces: magnitude and direction. Find the x & y components of each force, then add them up and get the magnitude of the resultant force.

 

[mustang]

I use Coloumb's law and each of the other charges given to be multiplied by 3.6*10^-6. So I got -12.44769231 with q_2=-6.5*10^-6,
-4.213065089 with q_2=-2.2*10^-6, and -17.42676923 with q_2=-9.1*10^-6. I added all three and I got -34.08752663, is this correct?

 

[Doc Al]

No. You just can't add them, since they point in different directions. Find the x & y coordinates of each. Add them like vectors.

 

[mustang]

How do you find the x and y coordinates? If I start first by multiply 3.6*10^-6 by each of the other charges and comes were three different numbers what do I do with them?

 

[mustang]

Answer

Is the answer 21.305 Newtons?