## Energy Conservation

We will encounter many situations or many systems for which the

total energyremainsconstant. Energy may change from oneformtoanotherbut the total energy -- the sum of potential energy plus kinetic energy -- willremain constant. We describe this by sayingEnergy is conserved.E = PE + KE E = constant

PE + KE = constant

E

_{i}= E_{f}PE

_{i}+ KE_{i}= PE_{f}+ KE_{f}

Examples:Pendulum

Energy changes form -- from PE to KE and from KE to PE -- but the total amount of energy,

E _{Tot }= KE + PEremains constant,

Free FallEnergy changes form -- from PE to KE and from KE to PE -- but the total amount of energy,

E _{Tot }= KE + PEremains constant,

Elastic Potential EnergyNonconservative ForcesReturn to ToC, Work and Energy(c) 2002, Doug Davis; all rights reserved