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Conservation of Mass and Energy

Conservation of mass​

The law of conservation of mass states that the total mass of an isolated system (that has no interaction with surroundings) remains constant.

∑imi=const.\sum\limits_i m_i=const.

Conservation of energy​

The law of conservation of energy states that the total energy of an isolated system (that has no interaction with surroundings) remains constant.

∑iEi=const.\sum\limits_i E_i=const.

Conservation of mass-energy​

Special relativity states E=mc2E=mc^2, that any object with mass can convert its mass to energy, and vice versa. This is assumed to be possible only under very extreme physical conditions. Nevertheless, the classical laws of conservation of mass and conservation of energy are "broken" because of this proposal from Einstein. So they are combined as the law of conservation of mass-energy:

∑imic2+∑jEj=const.\sum\limits_i m_i c^2+\sum\limits_j E_j=const.

Nuclear fusion and fission​

Nuclear fusion is a process that occurs when the nuclei of two atoms are brought close enough together to form a heavier nucleus. Because the final mass is smaller than the sum of the initial masses, the loss of mass results in the release of a large amount of energy.

Nuclear fission is a process that occurs when a large and unstable nucleus of an atom (such as uranium and plutonium) is bombarded and split into two smaller nuclei. Because the sum of the final masses are smaller than the initial masses, the loss of mass results in the release of a large amount of energy.

Energy loss of ball bouncing​

If you let a ball free fall from a certain height, gravitational potential energy transfers into kinetic energy during the fall. If air friction is considered, part of the gravitational potential energy turns into thermal potential energy. In other words, friction generates heat. When the ball starts to contact the ground, kinetic energy transfers into elastic potential energy as the ball is compressed. At the same time, the compression also generates heat. As the ball starts bouncing back, the elastic potential energy is released back into the kinetic energy, and the kinetic energy transfers back into the gravitational potential energy as the ball goes up.