 In Chapter 1, we spend a lot of time reviewing dimensions and property definitions, and for the content that has already been covered in Thermo 1, I am going to be brushing over that. There are just a few notes I want to make on Chapter 1. First of all, the definition of a fluid for our purposes is anything that changes its shape to conform to a container. So that means gases and liquids are both fluids for the purposes of this class. Next, we are going to be operating under the assumption that our fluids behave as a continuum. That means that we are neglecting scale effects, essentially. As you zoom in on the fluids within our hypothetical analysis, you just get more of the same. In reality, on very small scales, fluids begin to behave a little bit differently. We are neglecting that, we are treating it as a continuum. Our primary dimensions are going to be the same as in Thermo 1. We are considering mass, length, time, and temperature. And unlike Thermo 1, we are going to be using a lot of vector notation. So an analysis of a vector is going to include multi-dimensional data, and we are going to see this a lot with positional data, especially velocity and acceleration. While we're here, let me point out that we are using the notational scheme of u, v, and w for the x component of velocity, the y component of velocity, and the z component of velocity respectively. We will distinguish vectors with a half arrow or full arrow notation, as opposed to scalar fields, which will have no hat. Also note, when we assume steady-state analysis, that means that we can get rid of anything that changes with respect to time. For steady-state analysis, nothing can change with respect to time, so any and all partial derivatives with respect to time go to zero. The only real definition we need to make is that of a Newtonian fluid. In a Newtonian fluid, there is a linear relationship between sheer stress and sheer rate. The slope of that line, that linear relationship, we abbreviate with the Greek letter mu, and we call dynamic viscosity. Like with specific properties in thermal 1, it is sometimes convenient to try to eliminate mass as much as possible from our analysis, so another viscosity term that you will see frequently with Newtonian fluids is that of kinematic viscosity, which is abbreviated with the Greek letter nu. Kinematic viscosity is dynamic viscosity divided by density. Again, in a Newtonian fluid, there is a linear relationship between sheer stress and sheer rate. For non-Newtonian fluids, that relationship is anything other than linear. In some fluids, sheer thinning fluids, they may actually have less sheer stress with more sheer rate. While we're here, I will also point out that treating something as a Newtonian fluid is an assumption, a simplification that we make in order to try to contain our scope. Like with the assumption of a closed system or steady state analysis, it is simplifying reality to a convenient model for the purposes of analysis. Let's try a Newtonian fluid example problem.