in the figure four particles form a square

In the figure, four particles form a square. The charges are q1 = q4 = Q and q2 = q3 = q. (a) What is Q/q if the net electrostatic force on particles 1 and 4 is zero? (b) Is there any value of q that makes the net electrostatic force on each of the four particles zero? Explain.

[s.islambiddut]

Why negative and positive q and Q was assumed? --Because the net force is zero, as negative can cancel out positive so one was considered to be positive and the other as negative. WHY DID WE WORK WITH THE X COMPONENTS ONLY ? --Because it says net charge 0. i.e if we find Fy and Fx separately and then find the resultant {root over (Fx)2+(Fy)2}=O. When the sum of the squares of the two terms are 0, individually they will give 0. So Fx=O and Fy=O So finding only Fx or Fy will do instead of making complex calculations by taking resultant of Fx and Fy

[tesleemahdosunmu]

Why are you finding the Q/q in question (a) using the x component and in question (b) using the y compoment to find Q/q

[hskcmaverick]

thank so so much sir. i swear to got this make my day :)

[austinsears]

Thank you so much for this! Great video

[star]

Why are we looking at the x component only?

[nakibafarhanaswarna]

why use cos for F41 & sin for F23 ? someone please help me

[mounirarab]

Can I know from where did u get this exercise?
(name of the book)

[nikurou]

@ 5:35 Cos(45) is supposed to be 1/rad2 but he ends up getting the same answer as the one in the solution manual anyways. Am I missing something?

Edit: So coincidentally it just so happens that for the x component, using rad2/2 as cos(45) will give you the same answer as using 1/rad2. The answer for the y-component however would change.