Basic physics, interactions between multiple electrons

[tja2468]

I have always wondered about this particular problem, when three electrons are arranged in a triangle and the question was to calculate the force experienced by one of the electrons. My physics teacher taught us that we only care about the forces colored in red and blue, totally ignoring the black colored one. But then, wouldn't the black colored force affect the other two electrons and cause the magnitude and direction of the forces to deviate a little? I am aware that this is an extremely ideal model of electrons, and is unrealistic. Thanks in advance

 

[Doc Al]

When calculating the net force on charge 1, only forces on charge 1 count. The fact that charges 2 and 3 exert forces on each other has nothing to do with the forces they exert on charge 1.

 

[tja2468]

Thanks for your quick response, that was really helpful and cleared up my confusion :)

 

[maverick_starstrider]

the black line would be important if your charges were not fixed in place and free to move and you were interested in how the particles positions change in time. But you're probably not.