Nowadays it is demonstrated by Noether's Theorem. Note that this involves some fairly advanced math. The basic assumption (for the Theorem) is that the laws of physics don't change over time. Another kind of reasoning is by observation: in all known processes, energy is always conserved.
"Conversation of energy" is a good non example of 'conservation of energy'
law of conservation of energy
law of conservation of energy.
conversation of energy of electromagnetic
The law of Conversation of Energy
energy can not be created or destroyed, it can only change its form
It means that, assuming there if no friction, the sum of kinetic energy + potential energy doesn't change.
The law of conservation states that energy cannot be created or destroyed, only changed from one form to another. It is a fundamental principle in physics that governs the behavior of energy in the universe.
In physics, there is only one conservation of energy law. The law says that energy can't either be made or lost. Consequently, the sum of all energy remains constant.
With the law of conversation of mass you can balance anything.
According to the scientific law of conservation of energy the energy can be sustained by the bouncy ball indefinitely
The most important idea of the law of conservation of energy is that however and how much it is spent, energy is not lost nor destroyed, but only changes form.