Question

Why are conservation of mass and conservation of mechanical energy not considered fundamental laws of nature?

Answer 1

1. In physics conservation law of nature states that the particular measurable property of an isolated physical system does not change as the system evolves over time.
2. According to the conservation law of nature four quantities are always conserved which are linear momentum, angular momentum, energy, and electric charge.
3. Mass and mechanical energy are not conserved all the time. In the case of nuclear reaction, mass is not conserved.
4. Mechanical energy is conserved as long as the mass is conserved.

Hence, the conservation of mass and conservation of mechanical energy are not considered fundamental laws of nature.