Question

A cube of edge a meter carries a point charge q coulamb at each corner.calculate the resultant force on any of the charge

Answer 1

Let the charge you want to find the force on be Q1
Each of the 7 remaining charges applies a force on this charge.

Using Coulomb's law, the force on this charge is,
F = K x Q1 x Q2/ (distance between the charges)^2
Here, Q2 is the other charge (any one of the 7 charges)
And the value of K is 9 x 10^9

Mathematically, all you have to do is find the distance between the 2 charges.
After this, plug the distance into the formula and you'll get 7 different equations of forces of different charges acting on charge Q1.

Now, add all of the different forces and pat yourself on the back because you'll have solved for the net force on a single charge.