Potential Energy and Conservation of Energy Chapter 8 Potential Energy and Conservation of Energy In this chapter we will introduce the following concepts: Potential energy Conservative and non-conservative forces Mechanical energy Conservation of mechanical energy The law of conservation of energy will be used to solve a variety of problems. As was done in Chapter 7, we use scalars such as work, kinetic energy, and mechanical energy rather than vectors. Therefore the approach is mathematically simpler.

Physics of Bungee-Jumping One job of physics is to identify the different types of energy in the world.

8.2 Work and Potential Energy Change in potential energy, ΔU is defined as being equal to the negative of the work done, W on the object by the force.

Conservative and Non-conservative Forces A force is a conservative force if the net work it does on a particle moving around any closed path, from an initial point and then back to that point, is zero. Equivalently, a force is conservative if the net work it does on a particle moving between two points does not depend on the path taken by the particle. A force is non-conservative if the net work it does on a particle moving between two points does depend on the path taken by the particle. Examples Conservative Forces: Gravitational force and Spring force. Non-conservative Forces: Kinetic frictional force and Drag force.  

8.4 Determining Potential Energy Values

8.5 Conservation of Mechanical Energy In an isolated system where only conservative forces cause energy changes, the kinetic energy and potential energy can change, but their sum, the mechanical energy of the system, cannot change.