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# Conservation of energy

Conservation of energy – Explain That Stuff!

How was energy defined and discovered in the first place?

The Discovery of Energy Conservation: Mayer and Joule

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### Count Rumford’s experiments demonstrated that heat was a form of energy.

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### In 1843 James Prescott Joule found the mechanical equivalence principle

From machinedesignonline, at https://www.youtube.com/watch?v=uDrdaNcGpwo

### Joule measured the water temperature and found the temperature had increased. Yup, the water was a little bit warmer because the mechanical work of the paddles had increased the energy level of the water molecules by pushing them around.

http://www.ftexploring.com/energy/first-law_p2.html

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Ancestors of E = mc2 By David Bodanis: NOVA

David Bodanis writes:

### She survived the birth the next fall, but infection set in, and within a week she died. Voltaire was beside himself: “I have lost the half of myself—a soul for which mine was made.”

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## Energy is not enough

### Energy is not the only quantity conserved by nature.  Consider Newton’s cradle: Lift one steel ball, drop it, see what happens. Lift two, see what happens, and so on.  There are many possible outcomes which could happen, in which momentum is conserved, yet which never actually happen. This behavior can only be explained by two different natural quantities being conserved: energy and momentum.

The following image is from HyperPhysics, by Carl R. Nave

## Learning standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS3-1. Use algebraic expressions and the principle of energy conservation to calculate the change in energy of one component of a system when the change in energy of the other component(s) of the system, as well as the total energy of the system including any energy entering or leaving the system, is known.

Disciplinary Core Idea Progression Matrix

PS3.A and 3.B:  The total energy within a physical system is conserved. Energy transfer within and between systems can be described and predicted in terms of energy associated with the motion or configuration of particles (objects).