1. The problem statement, all variables and given/known data A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and increases the kinetic energy of the small sphere 2. Relevant equations 3. The attempt at a solution What I know: 1. The kinetic energy of the object is increasing. The system is doing work on it. It's transferring energy to the object. But at the same time the object is losing potential energy. So it's not really gaining energy. The amount of potential energy lost is equal to the amount of kinetic energy gained. Mechanical energy is still the same. But if it were I could say that the work done by the system (electrostatic force) is positive and the work done on the system is negative. (Is that also right?) So what is the correct answer? I am confused. I also have a little bit more confusion. What is the system? Is the system the particle in question, or is the system the object doing work on the particle such as the charge exerting an electrostatic force on it?