What does it mean for a physical system to be in static equilibrium

The free body diagram shows a box being pulled to the left up a 25-degree incline. the magnitude of the normal force is

The charge on a charged sphere is: a)concentrated at its centerb)distributed uniformly throughout its volumec)clustered on its centerd)distributed uniformly over its surface

Along the line connecting the two charges, at what distance from the charge q1 is the total electric field from the two charges zero? express your answer in terms of some or all of the variables s, q1, q2 and k =14ï€ïµ0. if your answer is difficult to enter, consider simplifying it, as it can be made relatively simple with some work.