1. The problem statement, all variables and given/known data A negative charge placed at point A is a)in stable equilibrium along x-axis b)in unstable equilibrium along y-axis c)in stable equilibrium along y-axis d)in unstable equilibrium along x-axis (There can be more than one answers) 2. Relevant equations 3. The attempt at a solution The particle is in equilibrium since the net force is zero. But the question asks whether the equilibrium is stable or unstable? I don't get it what the question means by that. What are the criteria for checking whether the equilibrium is stable or unstable?