How does one charge know the other is there?

E2 left a hole and did not mention it. Two objects, nothing between them, and a force. Nobody asked how.

You will need nothing.

No balloons, no bench, no dry day. You need a pencil and your own judgment. That is not a gap in the lesson. It is what the lesson is about. Some questions in physics are not settled by measuring harder.

This one works best after E2 · What decides how hard two charges push?, which is where the ideas it leans on come from. You can carry on without it.

Your predictions lock once committed.