1. Conservation of Energy
Work and Energy
Conservation of Energy

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

3. Conserved Quantities

4. 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

5. Mechanical Energy

6. 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

7. Mechanical Energy

8. 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

9. 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

10. Friction and Mechanical Energy