Which of the following is a true statement about the conservation of energy? a. potential energy is always conserved. b. kinetic energy is always conserved. c. mechanical energy is always conserved. d. total energy is always conserved.

Total energy is always conserved (Option D is correct).

Explanation:

Let's consider an isolated, conservative system.  The system can have kinetic energy K and potential energy U. The sum of the kinetic energy and potential energy is constant.  This means total energy is always conserved.

When the configuration of the system changes and work is performed on one of the objects, the potential energy of the system is transferred to kinetic energy of that object. This means potential energy is not conserved.

Kinetic energy is not always conserved for example, in an inelastic collision, kinetic energy is converted to another form of energy (heat, etc.). The sum of all types of energy (total energy) is the same before and after the collision.

In a perfect scenario, mechanical energy is conserved. BUT for example, friction causes some mechanical energy to be changed to thermal energy. In this case the mechanical energy will be les, what means it's not always conserved.

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation: