Given an equilateral triangle with different charges namely charge on A is negative 4nC; B is positive 2nC and C is 1nC. The sides are all equal with 20cm. How can you calculate the resultant field on A; the mutual potential energy of the system?

Answer 1

Field on A? it comes from charges at B, C.

You have to add the E=kq/.2^2 equation from charges at B and C as VECTORS.

I don't know what "mutual" potential energy is. Potential energy is at a specified point.