A 2 dimensional circle of radius "r" and mass "m" is attached through the center of the circle by a rigid, massless rod to a fixed point of rotation a distance "l" away. A massless rocket is attached to the outside of the circle a height of 0 away from the circle's surface and "r" away from the circle's center. The rocket exerts a constant force "F" tangentially to the circle. The system is ideal. How would I go about finding the total system energy with respect to time?