Final answer:
The work-energy theorem and conservation of energy are principles used in physics to analyze energy changes in a system. The work-energy theorem is used when both conservative and nonconservative forces are involved, while conservation of energy is used only when conservative forces are involved.
Step-by-step explanation:
The work-energy theorem and conservation of energy are both principles used in physics to analyze the energy changes in a system. The work-energy theorem states that the net work done on a system is equal to the change in kinetic energy of the system. It is used when there are both conservative and nonconservative forces acting on the system.
On the other hand, conservation of energy is used when only conservative forces are involved. It states that the total mechanical energy of a system (sum of kinetic and potential energy) remains constant as long as no external forces are acting on the system.
So, if you know that only conservative forces are acting on a system, you can use the conservation of energy principle to analyze its energy changes. If there are both conservative and nonconservative forces, you can use the work-energy theorem to calculate the net work done on the system and its resulting change in kinetic energy.