Final answer:
b) Conserved, potential, kinetic. The total amount of mechanical energy is conserved in a closed system. Mechanical energy is the sum of potential and kinetic energies, and these two forms can be converted into each other without any change in the total amount of energy.
Step-by-step explanation:
The total amount of mechanical energy is conserved in a closed isolated system, and can be converted between potential and kinetic energies. The correct answer is b) Conserved, potential, kinetic. In a closed system, mechanical energy, which is the sum of kinetic energy (KE) and potential energy (PE), stays constant due to the Law of Conservation of Mechanical Energy. As KE increases, PE correspondingly decreases and vice versa, without any net change in the total mechanical energy of the system, unless external work is done. This is because the energy in a closed system is not leaving the system but is simply transforming from one form to another.
Whenever work is done within the system, it can change the form of energy. For example, if we consider a swinging pendulum, at its highest point, the kinetic energy is at its lowest while the potential energy is at its highest. As the pendulum swings down, potential energy is converted into kinetic energy, which is at its maximum at the lowest point of the swing. Yet, the sum of potential and kinetic energy at each point remains constant, illustrating the conservation of mechanical energy.