Energy Conservation

NASAPhysics

Online Course

Conservation of Momentum & Energy

Equation

KE₁ + PE₁ = KE₂ + PE₂ = KE₃ + PE₃ etc.

2.5

Energy Conservation

The idea that energy is conserved within a closed system is not entirely new. Ancient philosophers suspected that there may be a fundamental substance from which all other substances are born. This prime substance was the root for water, air, fire, and earth. Thales of Miletus (624-546 B.C.), known as the father of science, attempted to describe the natural world from observation, hypothesis, and mathematics, instead of mythology and religion. He concluded that water was the principle substance from which the Earth and all other matter were created. He was wrong about water – the correct answer is atoms.

The conservation of energy means that the energy a system has at one point in time will equal the energy at any other point in time, within a closed system – with no energy coming from outside or leaving. This is expressed as:

total energy at time 1= the total energy at time 2 or any other time KE₁ + PE₁ = KE₂ + PE₂ = KE₃ + PE₃ etc.

Thales of Miletus, Wikimedia Commons