Conservation of Energy Work and Energy Conservation of Energy

Conserved Quantities Conserved – remains constant May change form Mass and energy are both conserved

Conserved Quantities

Mechanical Energy Mechanical energy – the sum of kinetic energy and all forms of potential energy Typically involves things we can see Not atomic or chemical energies Mechanical energy = kinetic energy + sum of all potential energies ME=KE+ΣPE Non-mechanical energy – energy that is not mechanical, such as nuclear, chemical, internal, and electrical

Mechanical Energy

Mechanical Energy Conservation of mechanical energy – in the absence of friction, the total amount of mechanical energy in a system is conserved Initial mechanical energy = final mechanical energy MEi=MEf

Mechanical Energy

Mechanical Energy Other than friction, mechanical energy is conserved in the presence of forces acting on an object Mechanical energy is conserved when an object experiences variable acceleration

Friction and Mechanical Energy Mechanical energy is not conserved in the presence of friction Total energy is still conserved Total energy is always conserved in non-nuclear reactions Friction converts mechanical energy into non-mechanical energies such as sound and heat

Friction and Mechanical Energy