4 Review of Conservation of Energy
Instructor’s Note
This unit, in fact this entire course, will spend a lot of time talking about energy: a topic covered extensively in Physics 131 as well as in your Biology and Chemistry courses. This chapter is therefore a bit different: we provide links to the relevant sections on energy from the Physics 131 textbook Forces, Energy, Entropy for your reference, with the key takeaways from each section. Just review what you need.
There are also a few homework problems at the end, just to make sure everyone is on the same page.
Relevant parts from Physics 131: Forces, Energy, Entropy:
- Unit IV – Chapter 2 Introduction: Introduction to Energy
- Unit IV – Chapter 2.1: Units of Energy
- Note, we will use the eV unit of energy described here much more in this class than in Physics 131.
- Unit IV – Chapter 2.2: Types of Energy and Scales of Energy
- It is important to think about the fact that there are fundamentally only two kinds of energy: potential and kinetic.
- Unit IV – Chapter 2.3: Conservation of Energy
- This is one of the fundamental of this unit (and all of physics). We will begin many problems with this idea.
- Unit IV – Chapter 2.4: Ways to Transfer Energy
- The key idea here is that there are two ways to transfer energy: and .
- Heat is the transfer of energy through collisions at the microscopic scale. This includes , an idea that will appear in a later section of this reading.
- Work is the application of a force for a distance .
- Unit IV – Chapter 2.5: The Formal Statement of the Conservation of Energy as the First Law of Thermodynamics
- The change in energy of a system is the amount going in or out as heat and work: . This is the principle from which we will begin many of our analyses.
- Unit IV – Chapter 3 Introduction: Energy of Objects as a Whole
- This is where the ideas of kinetic and potential energy as you saw them in 131 are introduced.
- Unit IV – Chapter 3.1: Kinetic Energy of an Object
- We will be looking a lot at the kinetic energies of electrons.
- Unit IV – Chapter 3.2: Examples Applying Conservation of Energy with only Kinetic Energy
- If you need to refresh how to use the kinetic energy formula
- Unit IV – Chapter 3.3: Macroscopic Potential Energy
- This is where the idea of gravitational potential energy is discussed. We will use this expression in this unit.
- More importantly, we will build an understanding of electrical potential energy in Unit III partially by analogy and comparing and contrasting with gravity.
- The arbitrary nature of the definition of zero of potential energy discussed in this section will also be relevant, and may be worth review.
- Unit IV – Chapter 4.1: The Potential Energy of Molecules
- The idea that two charges infinitely far apart have, by convention, zero potential energy will be relevant as will the idea that bonded electrons/atoms have negative potential energy.
- Unit IV – Chapter 4.2: Application of Bond Energies
- This is an example problem