Energy Conservation
We will encounter many situations or many systems for which the total energy remains constant. Energy may change from one form to another but the total energy -- the sum of potential energy plus kinetic energy -- will remain constant. We describe this by saying Energy is conserved.
E = PE + KE E = constant
PE + KE = constant
Ei = Ef
PE i + KE i = PE f + KE f
Examples:
PendulumEnergy changes form -- from PE to KE and from KE to PE -- but the total amount of energy,
ETot = KE + PE remains constant,
Free FallEnergy changes form -- from PE to KE and from KE to PE -- but the total amount of energy,
ETot = KE + PE remains constant,
Elastic Potential Energy Nonconservative Forces Return to ToC, Potential Energy (c) 2005, Doug Davis; all rights reserved