Final answer:
The correct equation that relates mechanical energy, thermal energy, and total energy when there is friction present in a system is Etotal = ME + Ethermal.
Step-by-step explanation:
The correct equation that relates mechanical energy, thermal energy, and total energy when there is friction present in a system is Etotal = ME + Ethermal.
ME represents mechanical energy, which includes the potential energy and kinetic energy of the system. Ethermal represents the thermal energy, which is the energy associated with the temperature and is generated due to friction. Etotal represents the total energy of the system.
Friction is a dissipative force that converts some of the mechanical energy into thermal energy, leading to a decrease in the system's total mechanical energy. Therefore, to account for friction, we need to add the thermal energy (Ethermal) to the mechanical energy (ME) to calculate the total energy (Etotal) of the system.
Learn more about Mechanical energy, thermal energy, and total energy in the presence of friction