Section C.6 Chapter Notes
Chapter 1.
Do we want learning objectives or key questions. We need to pick one or the other. Are we going to have them for the chapter, or for each section? Whatever requires consistency.
If key questions are asked, then then answers should be found in the section -- semi explicitly.
Caption to book_table fbd diagram 2.2 mentions fbd (a) but figure is unlabeled.
"The definitions below describe a few of the force types "... they aren't really definitions.
You only mention three types of forces, and not even all the ones on the illustration.
should mention the difference between mass density \rho and weight density \gamma, and maybe even specific gravity.
Chapter 2.
Tables:
I think that tables should be used to summarize information explained in the text. I have converted most to linear presentation with a list
Geogebra applets will need to be modified somewhat to look good on the page. Font sizes, aspect ratios, pan and zoom, colors. All need to be thought about.
It is a struggle to make geogebra applets fit in the width available. Requires a lot of trial and error. I will probably learn best way to do it eventually
right hand rule diagrams. premature to talk about crossing, and to use cross product to find direction of moments which have not yet been defined. Fixed
I need to adjust the nesting levels TOC max depth is 3.
Chapter
- Section
-- Subsection
--- Subsubsection
para or p
Probably should spell out most instances of 1D, 2D and 3D three dimensional?
Grammar says numbers less than 10 should be spelled out: one, not 1
3D coordinate systems:
I have a lot of problems with this section.
This is confusing a coordinate system with a vector space. They are similar, but certainly have different units, and possibly a different scale too.
should all be mentioned together as orthogonal systems. Don't downplay cylindrical systems, Mention that they are used to specify a point in space as well as used for vectors. Diagram shows angle theta measured the wrong way. I believe that polar and spherical are not synonymous. Polar coordinates are the r-theta system used in 2d.
I am not sure how effective hypothes.is will be while the source document continues to change. Will need to test this out.
I believe that the student survey about textbooks wanted lots of example problems. There are none in this chapter yet.
Need to figure out how to turn off figures/interactives in knowls.
I'm not sure what I think of dan's step-by-step process approach.
Example was difficult to typeset, but I think better than Dan's presentation as a table, which btw wouldn't be any easier to typset. The solution or problem statement needs a diagram. I want each step of the solution to begin with a well-known symbolic equation.
Fixed processing chain to retain quantities and remix elements in source.
Simplify example structure in chapter 3
Interactive 'instructions' render above the diagram, but it should be possible to change this in the stylesheets.
I can't figure out how to make xrefs go to the referenced element instead of in a knowl, but should be possible.
In the formulas involving projections 'proj' is rendering in italics. I have defined a projection operator \proj which renders it as roman, but I still don't like the notation. Is there another notation Proj_{b/a}? proj_b^a? Need to work on this.
Spell out and hyphenate three-dimensional but three dimensions, etc. Avoid 3D
The notation section needs some work. I do almost a whole lecture on just this.
Needs some numeric examples in this chapter.
Missing this interactive:
figure xml:id='vector_dot_product_3d'
Dot Product in Three Dimensions
Chapter 3.
The last two example problems are unfinished
A lot of duplication between 2d and 3d basic procedure.
Chapter 4.
In Figure 4.2.1 ... The perpendicular distance is not a vector, it is a distance. Diagram and discussion in Section 4.3 should be changed.
Notation - You say M_A means moment about point A. True, but what if you are adding the moments of several forces about the same point? What is your notation then?
I think the discussion of the mathematics of cross products: definition, how to evaluate, etc. belongs in chapter 2, with application of cross product to find moments in chapter 4. done 8/4/20
I think your notation for determinants is incorrect. The way I learned it, matrices are enclosed in brackets, determinants enclosed in vertical bars. You have it the other way around.
Moment about a line section peters out before finishing the thought.
In diagram "Example of a force couple applied to a rigid body" the distances d and a should probably have arrowheads at each end, since they are not vectors.
Interactive Figure 4.6.2 is really about scalar addition of moments in a plane. Should discuss this, and get rid of vector equation.
Interactive Figure 4.8.1 shows loads and the equivalent force/couple on the same object. Show show two rectangles and indicate that they are equivalent. Notation in interactive is not consistent with notation in discussion.
Chapter 5.
Introductory paragraph for section on free-body diagrams 1.1 don'ts start at the beginning. What/why fbd, then state it is critical
On free-body diagrams, every force, known or unknown must have a variable name. These are needed to write clear equations.
Known values should be stated F = 10 N.
I don't understand what you are getting at here:
"Supports provide the type (force or moment) and direction of support a body needs to resist applied loads"
This needs more careful discussion, particularly elaborate on the meaning of stable. Static, I believe we have defined as: not accelerating.
"If a degree of freedom is not restrained, the body is in an unstable state and is not static. "
A hockey puck sitting on ice is static, but not constrained.
"Choosing a pathway" example diagrams: point C is not indicated on the diagrams. Example needs to explain
"Rules to Validate a Stable and Determinate System." The rules are stated as questions, so you have not given rules.
In "degrees of freedom" ... not sure why you are discussing this in terms of movement, and not position, since this is statics.
Equilibrium equations and strategy sections need reworking. Wordy, redundant and out of order.
Need to add lots of example problems, tying back to the explanations.
General thought: Every chapter should conclude with a chapter summary. Get rid of any section summaries.
Chapter 6.
This statement “If two members meet at an unloaded joint, then both members are zero-force members.” is not always true. If the forces are collinear they are not necessarily zero forces.
This statement “Simple trusses, by definition, are statically determinate, having an equal number of equations and unknowns.” is not true. There are more equations than unknowns. That's why the last joint can be used to verify the the work.
Too many unordered list. Need to be fleshed out as paragraphs.
I have a different way of discussing zero force members.
Simple trusses section- needs reorganization. Combine last three subsections into a section called 'solving a truss' which should discuss what it means to solve a truss, foreshadow the two methods, talk about commonalities and general approach, then include material from labeling, reactions and zero force members.
Summary tables Table 6.6.1:
- This table is repeated from the beginning of the chapter... I removed it.
- Your definitions need to be more concise.
- Tables should not be used for instruction only be a reminder of important conclusions.
- Too much text doesn't fit will in narrow columns.
- Particle definition: you mean "concurrent" or "coincident" not "collinear" points are collinear if they all fall on the same line.
- Rigid body definition is confusing
- I don't understand this “Collinear forces allow us to isolate particle as free-body diagram (cutting axial forces in 2-force supports)”
Chapter 8.
Redundancy. I'm seeing a lot of it. We will need to clean this up later.
The text has a lot of procedures versus explanations. Need to think about if that's what we want.
Tables for layout and explanations. That's bad. Need to consider all these tables, and use them for summaries only
The term 'Axial' force should only be used for two-force members with an obvious axis, in other cases call it the normal force.
Typography in diagrams and interactive should follow math typesetting rules used in the text, so italics for variables, upright for units, et.
Don't use the same variable name to mean two different things. You are using A for the reaction at A as well as the axial force, which I would call the normal force. Especially confusing in the frame example where Ax and Ay are not the components of A??
Another reason I want more than red for forces is that it is very helpful on FBDs to use one color for knowns, and another for unknowns. Also color is helpful to differentiate different forces and identify which geogebra label belongs to which.
This is tough to accomplish, but in a series of related diagrams, the digrams should all be rendered at the same scale.
SVG images should have transparent backgrounds, so not to clash with the blue background in examples.
Arbitrary cut method second example is not finished. Needs to do the other two segments and produce the equations and plot them.
The local-global equation interactive needs some context
When deriving dm/dx you use dx/2 as distance to centroid of loading. This is sloppy and needs explanation.
Need at some examples which conclude with a complete VM diagram.
Need to work on geogebra applets for fit and consistency.
Chapter 9.
Should not say centroid on motorcycle and sled, but center of gravity. Not the same.
Diagrams need to reduce embedded text, and use latex for equations.
Explanations for diagrams need to be moved from caption to adjacent text and captions shortened.
Slip/tip. Section calls it slip, picture call it slide. Pick one,.
Belt friction derivation. \beta is not defined on the picture. Math is a bit sloppy - variable of integration is \theta, but limits are from -\beta/2 to \beta/2. Diagram shows dS, but this is not used.
Slip vs tip argument -- replace f_push with P, F_g with W, F_N with N and F_f with F. Confusing and unnecessary to use subscripts.
In wedge, figure 2.8, "Detail of N_1 & F_1" components are broken out as triangles, which is in contradiction to advice given previously.
In general, on diagrams give points names, and use those names for the forces, so on fig 2.8 Roller contact at A, call the force there A. Notation( roman \(\text{A}\text{,}\) point. \(\vec{A}\text{,}\) force. italic \(A\text{,}\) magnitude of \(\vec{A}\)\()\)