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AP Physics C A (Period 4) Assignments

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Assignment

Worksheet 12.1
 
Let's make it homework, the last assignment of the semester. I've mentioned it a couple times, it's easy and quick, it's interesting, you can race the round items in class, and it's a powerful practice final exam question, so I don't feel bad about saying do that for credit anytime this week.
 
The intention of this isn't to bombard with time-consuming things at the last minute. It's to give closure and credit to something that people could have already worked on. And if I'm wrong and there isn't time to do it, then it won't be held against anyone. Looking at it and seeing that it's the quick and easy problem of the unit is an important thing to do. If you don't agree that it's easy, it's really easy to let me know that and set you on the easy track.
 
The idea is that the circular cross-section items all end up at the bottom of the hill with an instantaneous speed equal to the square root of (Some number times gH).
 
But the "Some number" coefficient is different, depending on whether it's a hoop, sphere, or disk.
 
Should be fun and easy. Let me know if it's not. I'd like to make it credit. Anytime by Friday.

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Final Exam Free Response #2 Rubric
 
The attched document defends the claim that 13.93 out of 15 points of the Free Response Question 2 on the 2020 final were predictable Gift Points.
 
Please note: I haven't graded any student responses yet. I don't know what scores any individuals got. I'm pointing out what points any person could get with little test-time effort. The "any person" here means someone who did their reading and learned the terminology.
 
There's no statement here telling a person what they're supposed to earn. The rubric simply says things like "these two particular points were gift points" mainly because I either told people it was coming or some other such thing that only requires eyes be open. I'm not going to say, "You have to take the gifts." However, I do say, "This is how points are awarded in this course. The choice is yours." People who don't know they've had this choice have had their eyes closed to certain things.
 
I'll make another such rubric and Gift Point claim for Free Response 3 and post it as soon as I can. The Gift Point count on Free Response 3 will not be as high as 13.93 out of 15. One who reads the rubrics could easily see why.
 
FR2 has all but one raw point as freebie, because I told people exactly what they'd be tested on for #2, and I told them months ago, and then I told them again more recently with examples from old tests. People who don't take the gift points but claim they want to are people who make communication errors, not physics errors. I can point out such errors. I can't tell people what to do, so this isn't criticism. It's mere facts. And remember, I state this still without grading student responses from this year yet. So in these statements, I'm being as objective as I possibly can.
 
Semester 2 will continue to have gift points that are vocabulary and reading dependent, and more so, because the terminology will relate to electrical quantities which can't be seen with the naked eye, unlike this past semester.
 
It's also worth noting that life's too short and difficult to make academic tests be anything but simple. Why would the test writer ever intend to make them complicated? In any instants where after the test a test-taker reports a test item as complex or time-consuming, they are in all cases erroneously characterizing the items as complex or time-consuming in places where they're not. Any person can be aware of the point-scoring game that is inherent to any test, and that's why I point out the gift points.
 
Electric field and Electric Potential will be a topic in Semester 2 whose test grades will either be close to 100% per individual or very low per individual with little middle ground, and I never apply any AP scaling to it, because it's not timed. (The scores go into the gradebook as raw score and 85% is an A, 70% is a B, and so on.) This isn't a threat to create motivation. It's a topic whose skills come directly out of reading and practice, and students either do it or don't. It will be inappropriate to claim that the 100%-earners did so because they're smart. That particular test will be entirely full of predictable skills to apply. I tell the class in advance.

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Nothing accepted for credit after Friday, January 17, 2020

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Answer to a short problem from class:
 
If a coffee can is sitting vertically with its open side up and its circular flat bottom against the floor, then how high above the floor is the center of mass of the coffee can? Answer as a fraction of H, the height of the can. The radius of the can's cross-section is (0.4)H.
 
Deriving the answer was a strong recommendation on 1/13/2020 between 8 and 8:30 AM. The answer to derive is (5/12)H.
 
Consider how this effects the handling of both the moment of inertia and the full system center of mass (counting yellow rod) in the Compound Ballistic Pendulum problem. Everything you see from me treats the can as a particle with the can's own center of mass at its geometric center. You may now numerically evaluate the percent error that is made by my simplifying assumptions.

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Rotation Quiz Key
 
This isn't all the way done. I want THREE separate alternative solutions in the file. At the moment, it's only one. I'll add the other two when I get a chance. A person should want efficiency and checking by doing the problem a second way. That's quality control.

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Compound Ballistic Pendulum - Success!
 
I finished the problem based on student-driven data and the ball speed is a good answer. Nice job
 
Data Set:
 
Turns out you need way more than just two masses.
 
Can Mass = 113.3 g
Stick Mass = 321.75 g
Ball Mass = 9.9 g
h = the height the center of the can rose as a result of the collision = 0.783 cm
D = the distance from the suspension hole to the can's center = 1.0 m
d = the distance from the suspension hole to the Can/Stick/ball system's center of mass = 58.9 cm
y = the distance from the midpoint of the stick only to the suspension hole = 42.5 cm
L = the length of the overall stick when no can is attached = 105.2 cm
 
No write-up needed. If you can just determine (yes, put the data set first in writing (as always) and then show work on the problem) the ball's can-entry speed, and get it right on the first try, you can earn an experiment assignment A+ grade. Honor system. Each person does their own by themselves. Getting it right on the second try could earn some kind of A as well.
 
Note: in getting d above, rather than theoretically derive it, some of us just put the full system on our finger and recorded where it balanced.

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7:09 PM, Wednesday, January 15:
 
Stop working and rest soon.

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This is not an assignment or answer sheet or whatever!
 
Correcting a typo on a recent document that is NOT urgent. The document is "Cranking Out The Compound Pendulum." The solution notes in the meat of the document were correct and worked with a mass of 1 kg for the ball. The final answer stated in the key is accurate, because it correctly uses 1 kg. But unfortunately, on Page 1, the typo says that the ball's mass was 2 kg. Not a big deal at this point, but I simply wanted to confirm, because someone asked.
 
It might be interesting to note that this document has been given to my classes for about 5 years now, with the error in it, and this is the first time a student has pointed out the error, which is glaring when one reads the document.
 
The attached version of the document now has the error underlined and the needed correction notes on Page 1. But no one is supposed to work on it. It's bed time.

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First of two afternoon physics question times is happening in Room 206 right now (Tuesday). The other is tomorrow after school, meaning after 12 Noon.
 
The person who asked for the time Wednesday agreed that 1 PM would be good. This is so lunch could be had. I can go either way regarding noon versus 1, but a little break would be nice as opposed to getting right into things at noon. But I can handle it either way. I'll be here at noon. I'll be here at 1. To do questions on problems that people tried.

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Assignment

Omega-90 Data Sheet Update - January 13, 2020
 
This is raw class data and refined theoretical calculations for the 6 initially accurate measurers. People from that group of 6 know why there was a refinement. No one else need concern themselves with it. Everyone does need concern themselves with the raw data. These are the values being committed to. If one doesn't speak up, it means one agrees to them.
 
18 of 23 student entries are in here. It needs to be 23; the reason it's not is different forms of imprecision, incompletion, or lack of communication of clear data.
 
This write-up can be handed in anytime before the final. It's not complicated.

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Omega 90 Labwork Result - Has some connection to testing on the rotation unit and a huge connection to the second-to-last experiment of the semester.
 
To have earned credit on the Omega 90 HW, one's numerical entry must be complete and lead to a percent error in the attached spreadsheet. Anyone may look and see if they earned this credit. Any row full of Divide By Zero means credit was not earned. To be prepared means to know what R meant, and I said this specifically before break. I will later show photographic illustration of why R can't be as high as 35 cm. I accepted a small range of R's as valid. A data set can't be credited without a proper R, because no other measured quantity is unique to the unit of study called Rotational Dynamics. Those who omit a proper, realistic, relevant R don't receive rotational homework credit, because the remaining entries of the data set are Sensor Gap divided by time to get v-90, and this isn't a 7th grade experiment. (Speed equals distance over time being a middle school lesson.) The full unique data set requires this set of values: (R, t, d, x) where d is sensor gap distance and t is sensor gap time.
 
I noticed that some people didn't measure to the middle of their point mass, and that is very wrong, but I wasn't set up to evaluate for that.
 
The remaining instruction breaks the class into two groups, and whichever group you're in, you need to read the instructions given to both groups:
 
1) People who have a full data set in this attached spreadsheet: You have been rewarded in many ways. You are eligible to win the Percent Error Contest (and I think we easily have our winner.) I also gave you the gift of telling you what your theoretical Omega-90 is going to come out be if the theoretical physics problem is done correctly. But this doesn't let you off the hook. When you formalize the write-up, you are still going to have to show the derivation of that result. And notice I did NOT show you the value of moment of inertia that your system has. The moment of inertia correctly done is the most effort-filled part of the theoretical calculation. To get full credit on the lab assignment write-up, you still have to show a well-defended moment of inertia followed by the physics solution that leads to theoretical omega. Separate from the moment of inertia, the second most effort-filled part is deriving the value of the gravitational potential energy lost by the system. This is dependent on knowing how far the system's center of mass descends in the trip from horizontal to vertical. So you'll need to show clear work in the calculation of center of mass position. I treat it as a two-particle system where the rod is handled as if it were a particle located at the rod's midpoint. The incorporation of moment of inertia, center of mass, and loss of gravitational U into a coherent solution that applies conservation of ME is probably visible somewhere in some other notes of mine.
 
2) People not represented in this attached spreadsheet: You will be doing a theoretical prediction of Omega-90 for the x value that I assigned to you. The moment of inertia correctly done is the most effort-filled part of the theoretical calculation. You will show a well-defended moment of inertia calculation followed by the physics solution that leads to theoretical omega. Separate from the moment of inertia, the second most effort-filled part is deriving the value of the gravitational potential energy lost by the system. This is dependent on knowing how far the system's center of mass descends in the trip from horizontal to vertical. So you'll need to show clear work in the calculation of center of mass position. I treat it as a two-particle system where the rod is handled as if it were a particle located at the rod's midpoint. The incorporation of moment of inertia, center of mass, and loss of gravitational U into a coherent solution that applies conservation of ME is probably visible somewhere in some other notes of mine.
 
Whichever of the above two groups you're in, the smart thing to do is to derive Omega-90 as a symbolic function of x. Taken as a class, x is the independent variable, and a graph of Omega-90 versus x for the class is an important part of this experiment's write-up. So set up conservation of ME symbolically in terms of x, and derive Omega-90 as a function of x. The constants in the expression will be M, m, L, and y. M is the point mass's mass. m is the rod's mass. L is the length of the entire rod. y is the distance between the rod's pivot point and the end of the rod closest to the pivot point. y is only 2.5 cm. The values of the rest of those constants are in the spreadsheet. M is never placed between the pivot point and the closer end of the rod.
 
In class, I talked about the point mass being treated not as a point and taking its own dimensions into account when calculating moment of inertia. A good exercise for you to do is a proof of why why I'm now treating those dimensions as negligible and am back to treating M as just a point that is nothing more than a point mass of mass M a distance x from a pivot axis. Is this valid to do? Is it an OK approximation? Is it a great approximation? There is a specific answer to this question that's defended by numbers and only by tackling it can you consider yourself complete in the topic of moment of inertia. If it doesn't get asked about in class, it means that each individual has completed the proof on their own and is responsible for the concept.
 
The solution of Omega-90 through conservation of ME methods is considered one of the easier, more basic Rotational Dynamics topics that's considered fair game for any test on Rotational Dynamics. People who want to be thorough should realize that they use this as a review of more topics with more problems that could be solved beyond what I prompt you for:
 
1) Express the net torque on the system relative to the pivot point at the instant of release.
2) Express the angular acceleration of the system at the instant of release.
3) Express the net torque on the system relative to the pivot point at the instant when the rod is 37 degrees below horizontal.
4) Express the angular acceleration of the system at the instant of question 3.
5) Use conservation of ME to solve for Omega-37, AKA the final instantaneous Omega achieved at the instant when the rod is 37 degrees below horizontal.
6) 37 degrees is 0.646 radian. Investigate whether the formula
 
2(theta)(alpha) = Omega-final squared - Omega-initial squared
 
is a formula that holds up for the scenario of traveling from horizontal to the state that is 37 degrees below horizontal.
7) Dig deep into the conceptual reasons for WHY #6 either says "Yeah, it holds up" or "No, it doesn't hold up."
 
Without me giving away more than I want to give away for this experiment, I can post answers to the 7 questions above as they apply to the 1993 exam burning-thread-stick problem. I'll probably do that. I've re-attached that burning-thread-stick problem here so there is no confusion about what I'm referring to. And I have a pdf with the solutions to that year's Free Response.
 
If I post the 7 questions applied to the burning-thread-stick problem, you should realize that that helps immensely with the Omega-90 problem, because you're supposed to know by now that the only difference between the two is a different expression for moment of inertia and different distance to the center of mass. But the solution structure into which those two elements (moment of inertia and center of mass) are imported is identical.
 

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UPDATED: 6:30 PM on January 8, Solution Document Attachments Added
Cat Problem Attachment has answers on its latter pages. (You only got Page 1 of it as hard copy in class.) It references comparison to something called The Mallet Problem. If you don't have time to look at The Mallet Problem anew, that's OK. Instead, you could compare the Cat Problem to the 1993 Burning Thread Problem. But The Mallet Problem is pretty quick.
 
Reminders for Unit 12 Quiz:
 
While the quiz won't cover every single thing in the unit yet, it should have become clear through recent applications that the following skills are stressed:
 
1) Ability to determine moment of inertia for any object composed of the common shapes: points, rods, hoops, disks, spheres. This could be for the axis of rotation through any point in the system, so one must also know the parallel axis theorem.
2) To know the moment of inertia expression for a common shape about its center of mass, nobody must do an integral or memorize anything. The chart of common shapes' I's relative to their center of mass will be given.
3) To know how moment of inertia is applied in situations that call for Conservation of ME where K might be rotational and expressed in terms of omega.
4) To know how moment of inertia is applied in situations that call for Net Torque = (I)(alpha), and to know how lever arm is used in evaluating Torque as r X F.
5) To know how to draw perfect free body diagrams and have clear intention to use them in the process of setting up Net Torque = (I)(alpha) alongside Net Force = Ma. To know that the perfection of free body diagram drawing now requires that force vectors are located at their correct spot. Anyone who doesn't know that this last point is crucial because the location of force is what defines leverage in "Torque = r X F" is someone who is extremely far behind.
For example, no matter what I do to point this out, there always end up being people who say that gravity's torque in the burning thread problem (1993, look at it now) is MgL. This represents complete lack of physical awareness and physical definition. Actions speak louder than words: The action of writing "MgL" as gravity's torque is the same thing as shouting loudly to the world, "In that problem, I think all of the weight of the uniform rod exists just like a particle that represents ALL the mass located ONLY at the far right end of the rod." Such a notion is nonsense. It should be treated like ALL the mass located somewhere, but that somewhere is somewhere else, obviously not the right end.
6) To know how center of mass position is applied in situations that call for Conservation of ME where changes in U are still understood to be present and where the sign of U's change is to be understood.
7) The willingness and fluidity and lack of hesitation required when one needs to convert from alpha to a, omega to v, or theta to tangential distance. All of these involve radius, and one must physically understand which radius to multiply or divide by. 26% of the class passed the test on this basic piece of knowledge on January 7, 2020, and there is no Unit 12 understanding at all without it. Have fun speaking German while I speak English if you choose to remain in the 74%.
8) Be ready to continue to apply basic translational methods in the midst of a "rotational problem". There is no such thing as a "rotational problem". Be ready to apply everything learned; have a habit for setting up both translational and rotational relationships. For example, when the 1993 fake test told you to solve for the beam's acceleration of center of mass and also for the force exerted on the beam by the axis, was your habit to Diagram ALL FORCES and set up "F = Ma" as it always was supposed to have been by now? Did you do it like it was breathing? Did you then take that basic set up that's as old as October and add "a = R(alpha)" to it and add "Net Torque = (I)(alpha)" to it? If not, your eyes aren't fully open.
 
It would be very wise to apply the basic moment of inertia expressions and the parallel axis theorem and express the moment of inertia of the Omega-90 rod as a function of M, m, x, L, and y. It would be very wise to do this before January 9. This is because it's clearly needed for the theoretical part of the Omega-90 Experiment, and it should be obvious that doing that one is strong test prep. I'm not going to put that shape on your quiz, but the application skills in getting it are the same application skills used in whatever shape I will give you on that quiz.
 
It would be very wise to apply the definition of center of mass position and express the distance from system center of mass to the pivot for the Omega-90 rod as a function of M, m, x, L, and y. It would be very wise to do this before January 9. This is because it's clearly needed for the theoretical part of the Omega-90 Experiment, and it should be obvious that doing that one is strong test prep. I'm not going to put that shape on your quiz, but the application skills in getting it are the same application skills used in whatever shape I will give you on that quiz.
 
I'm working hard to post two more solution documents related to recent practice tests by 6 PM on Wednesday Jan. 8.
 
And in one of them, I'd like to close a loose end I brought up on January 7 that said, "In the Omega-90 beam, do you have to treat the point mass M like a distributed rectangle or is it safe to just treat it as a point in the moment of inertia? How safe?" You should remember me bringing this up. I then wrote the first couple terms in the total moment of inertia on the board. At the end of it, I said, "Complete the Moment of Inertia expression for the whole system. You'll need to look up the parallel axis theorem in the process. I'm hoping to include in a solution document some facts that reveal what you should have ended up writing for that.
 
For Omega-90, you shouldn't be waiting for my verification on whether you're getting the I correct or the center of mass position correct. You should write what you think those are and then be factoring them into the Conservation of ME theoretical solution for Omega-90. Your own measured Omega-90 is supposed to verify how you're doing. As of 1/7, 26% of Period 4 were eligible to do that, because they knew how to measure. (And everyone who did know how to measure got pretty low percent error, so this experiment is very good for teaching.)
 
100% of the population could know how to measure correctly. The latest attached version of the spreadsheet now assigns to everybody the R that was reported by the contest winner*. The rest of the data will be as reported by individual students on the papers I had them give me. I'll fill in the rest of the data to each individual when I get a chance.
 
*It's pretty interesting that the contest winner carried his R to 4 digits.

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Help With Moment Of Inertia Expression In The Omega-90 Experiment
 
1 page attachment
 
Last thing I'm posting on January 8
 
The bottom of the page addresses a loose end from January 7 which you should still ask about in class.

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Points
 
If my counting is correct, there have been 273 points in the gradebook so far. Anticipating 4 more graded things before the final, I see this going to 323 before the final. Then the final itself will be 50 points.
 
The 323 is a good estimate, but isn't claimed to be exact. It assumes a rotation quiz on January 9 as 15 points. But what if it only adds to 14 or whatever? Scores that will happen in the last week for sure:
 
Omega-90 Homework grade - 10 points
Omega-90 Experiment completion grade - 10 points
A Units 11 and 12 quiz on Thursday Jan. 9 - Probably 15 points
Compound Ballistic Pendulum - 15 points. Might only be one apparatus for the whole class. We'll squeeze it in in whatever way possible.
 
All four items above will definitely fit into the week of 1/6 through 1/10. The plan for them is very clear and definite. I'll make another posting soon with a reminder about what "Omega-90 Homework grade" means. It has to do with being ready for precisely and carefully measuring the Omega-90 stick. Both Omega-90 Scores will be taken care of by the end of January 7.

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Final Exam Facts and Prep:
 
You should be using this site over and over and over and not waiting to start, because it takes time for communication habits to develop:
 
 
Your final will have three Free Responses. See attachment.
 
Then there is multiple choice.
 
You start early and you train for the two test types (MC and FR) if you want to have a simple time earning points that are well over the 4 cutoff. More of the points on the final are FR as you'll see if you read the Info document.
 
And every year, the scores on FR2 and FR3 are 5's and 1's. Very little middle ground means that people either follow my directions leading up it or they don't. FR2 is fluid resistance oriented. FR3 is something from Units 11 and 12. Knocking it out of the park on FR2 and FR3 gets a person most of the way to a 4. Weak scores on the exam as a whole are usually people who do little to prepare for FR2 and FR3. But it's fully prepare-friendly, and every year, quite a few people earn many points on them.
 
Maybe you'd like to see an example of what I'm talking about regarding awareness and keeping eyes open and preparation. I present to you the FR#2 version that I have on the final two years ago. Scores on it were either extremely weak or 100%. The discussion in the key addresses this. I advise you to be a person who does it for practice without looking at the key. And then eventually when you do look at the key, figure out what it takes to be on the right side things.
 
And it gets better. I also post the 2015 FR#2 for practice. And the key to it was given to the students of two years ago with big cautionary tales to them about how to prepare. So this:
 
https://www.youtube.com/watch?v=Z_vvex_mfik
 
As we get into January, I'll start posting some Unit 11 and 12 type ideas that are supposed to be the same topics as FR3. Ideally, I shouldn't have to. Just prepare for that unit the right way. The Unit 11 and 12 graded large quiz is on Thursday, January 9.

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Studying for Rotation, Units 11 and 12 - Timeline
 
First of all, I gave you the material. Break it up in any way you want. The Large Quiz is on January 9. But if you'd like advice on what's a good bare minimum set of stuff to try by January 7, it's this:
 
- The Mallet Problem
- The Problem 2d Solution Breakdown
 
These cover both Newton's 2nd Law incorporating torques and Conservation of ME when K-rot is involved. That's a good set of stuff.
 
Do whatever you can, but if that were all you did in the Unit, I could set you straight on the rest in class on the 7th.
 
Among the attachments, the following were not handed out in class as hard copy:
 
- Notes 5
- Notes 5A
- Notes 6 - Notes 6 end the unit.
- Unit 12 Solving Strategies - kind of chatty I think

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Explanation of how the score Named HW8 will be credited:
 
In the attached spreadsheet, the place where raw data will be entered will be the three columns that are not Omega in the block called "Measured Results". Omega will be a calculated value that is based on v, and v is based on the raw data entries. You'll need to know the math that takes one from v to omega. Each person is to prepare for doing this as individuals.
 
You were supposed to know the following from class, but sensor gap is the tiny distance that the stick covers when going from one infrared beam to the next. And the time column will contain the tiny amount of time it takes to traverse the sensor gap. The radius R is the carefully measured radius that one will use in going from v to omega. The v and the omega being referred to are v-90 and omega-90. v is simply tiny sensor gap divided by tiny time.
 
You may look at the attached spreadsheet to enhance the clarity of what I'm talking about.
 
Why this is called:
1) Because to measure correctly and efficiently during the class of January 7, you will have to know what you're doing. To know what you're doing, it takes some prep and thought and diagramming and interpreting ahead of time. A lot of physics is learned by adjusting to the PRECISE physical meaning of the symbols I'm naming in this posting.
2) By the end of class, each individual will need to have reported a coherent set of the 4 raw measured quantities: x, time, sensor gap, and R. To get homework credit, the following will have to be true:
 
- The raw data have to lead to a measured omega-90 that's realistic. You don't have to know what "realistic" is. My spreadsheet will know.
- The raw data set that you report has to be a set of numbers that's physically possible to exist.
 
So it's homework because the numbers don't have to be registered until about halfway through class, but to be prepared to do measure right, each person has to do some prep work. Have a good ruler ready to go. Bring your own, and bring one that's long enough. The black stick is just over 38 cm long.
 
Finally, the sample file already has x's filled in. That was just to give you a sense of it. I'll be deleting those x's and putting in whatever x you have done or have assigned to you.

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Key
 
10 points and 4 points possible, adds to 14. Tasks that are about 10 minutes of effort total. No special scale. It doesn't warrant it.

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Monday December 16, 2019 had important white board exercises that needed final answers posted so a person could check to see that they were doing them right.
 
That's what these documents are. It's now or never on these, and it's to be brief. The Rotational Analogs one has to be common knowledge from now to the end of the semester. The Ugrav one is a concise Conservation of ME piece of review and critical thinking.
 
More importantly, the Ugrav one contains the important link to old AP exams and AP test equation sheets.
 
These documents are one page each.

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This was designed to help give physical examples for the Chapter 9 reading. It can also be worth a bunch of credit if a student chooses. (The reason I say it that way is that a student who did it in a prior physics class might see it as repetitive busywork.) For those doing it for credit, anytime during the week of 12/16 through 12/20 is fine with me.
 
If it's now a later date, it can be done but now for only 10 points possible.

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The momentum quizzes are completely graded. Many are strong.
 
Commonly stated meaningless statement in the world's physics classes (but less so in my class if this quiz is any indication): "ME will be conserved because there are no external forces." If it's stated, it means you can back that up. I'd like to see that one backed up with some algebra. It seems to me that gravity is external force acting on a frictionless roller coaster and the same people who say what's in quotes above have no trouble saying "Mgh = (1/2)Mv*v to solve for v, which amounts to the same thing as using ME conservation applied to a system that clearly has external force acting on it. So I don't really relate to the habit of stating something like "ME will be conserved because there are no external forces." when it can't be backed up in a basic way.
 
And nothing in my notes has stated anything of the kind, and neither has the textbook and neither has any other physics teacher's notes, so I'm not sure where people in the world are getting that from. Why say it if you don't actually know what it means? It's obvious by now this is not a soundbyte regurgitation subject. No superficial comments
 
On the other hand, I have very deliberately illustrated that "ME is conserved in the presence of external forces that are path-independent" and "ME is conserved during situations that have no path-dependent forces." Internal and external had nothing to do with it.
 
I have also very deliberately illustrated that "ME is conserved in the presence of external forces that are conservative" and "ME is conserved during situations that have no nonconservative forces." Obviously, internal and external have nothing to do with that either.

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Simulations
 
The Collision 1 is for Chapter 9 interaction stuff

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Important Timeline and Credit Announcements:
 
On Monday Dec. 16 will be a simple comprehension-style quiz (15 points) that covers the Intro Chapter 9 Ideas that were stressed in class on Thursday Dec. 12. To be prepared for this are many tools:
1) Work through the attachment "Chapter 9 (AKA Unit 10) Intro Notes – Part 1 2019" for sure. It's similar to the Dec. 12 lesson but has more in it. Do it all. It's a simple step-by-step thing.
2) Worksheets 10.1 and 10.2 are good. I handed them out on Dec. 10. The two-dimensional collision part of Worksheet 10.2 would not be quizzed. The quiz is entirely for motion on a single axis.
3) Read the book - Chapter 9
4) Nobody has to do a thing called "Collision Pattern Summary Assignment" by December 16, but if one had extra time, it would help. When it's ready, "Collision Pattern Summary Assignment" will be available in a separate internet announcement. The hard copy version you have so far can't be started yet, because you need one more page of info.
 
On Wednesday, Dec. 18 is going to be a large quiz (at least 15 points) at the mastery level on Conservation of Mechanical Energy and Work.
 
The two quizzes above are not out of order. They are different kinds of quizzes. The Monday quiz is not a mastery-level physics quiz. It's an intro level, vocabulary-style, following directions, reading comprehension, making sure people stay caught up quiz. The Wednesday one is sophisticated mastery level but only on things through Chapter 8. The mastery level nature of this is why I wanted to be so fast and efficient in grading the Bungee Experiments. And I have been.
 
On the second Period 4 meeting after break in 2020, we are going to have a large quiz on center of mass and moment of inertia. More material for that will come later.
 
And soon after that will be the final. There will be several postings starting in the next few days that are structural prep for the final.
 
These dates are rigid. Strength-building is over. Now complete the work and execute.

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Assignment

Major Schedule Change Announcement
 
The school changed the last week before break. The Boat Race is now Tuesday, December 17. That is one day sooner than previously expected.

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Assignment

Action required by Friday, December 13 for certain students in Period 4:
 
People whose names are in the list below had easily gradeable Bungee Slide lab reports, and all were fun to read. People whose names are not on the list cannot receive credit as of now, and I don't know if their papers are fun to read, because they didn't make it data-entry-friendly. A person who doesn't make it data-entry-friendly either was never on board with the actual objective of the assignment or they failed to consider a clear plan of what givens a reader needs in Data in order to know how to predict what will happen. If all the necessary info wasn't there or in some cases was uninterpretable through lack of units, the paper immediately went in the reject pile. I went above and beyond to show what clarity means on this, and I'm not spending even more time trying to interpret lacks of clarity or failures to define things the way it was agreed upon in class. For example, how am I supposed to know what a writer means by "equilibrium" position. There are two separate interpretations of "equilibrium" for this. People who briefly define things in words clear this up. Others use the word without clear definition, and it likely leads to the reject pile. I'm not guessing or working hard to interpreguess.
 
It should be the job of the people whose names are not on the list below to come to me to get theirs in order to try again, and their job is to do it on Friday 12/13. It's not my job to find them on campus (even though I sometimes do that.) I'm neither crediting nor reading the ungradeable reports the way they are. It's not my job. I'm already going to be spending too much time in having to have another sit to look at a subset of them again when they get turned in the second time for late credit.
 
Already gradeable (and therefore graded) reports belong to:
Burad
Davis
DiCamillo
Guo
Lok (graph resolution winner - most graded good ones failed to scale the graph for precision)
Maemoto
Moore
Velazquez (highest clarity winner)
Will
Welcher
Yang
 
Furthermore, a person who has trouble following the directions the way I told them need only look at the written lab report example that I posted for this. It's a crystal clear restate of the thing I said to do verbally more than once.
 
Group lab reports were never authorized for this. Those who guessed never bothered asking. If your name is not explicitly on the list above, as an individual, then you are considered not credited for this.

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Assignment

UPDATED 3:45 PM on Wed. 12/11:
Lab Report Sample Document DONE - Specific to Bungee Slider
 
I see no reason to make this report any more complicated than the example I have posted here.
 
Given the immense support and time for completing this, there will be no talk of this report on Thursday 12/12. It will simply be handed in as you arrive. Just give it to me, and it should be as easy to grade as this sample posted here. My plan is to take what you tell me in Data, put the numbers in my spreadsheet, be able to see in a column what your answer should be and green stamp yours if we match on the final answer and if your communication was clear and full of units.

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Assignment

U Versus Position Graph Elliptical Orbit Application - Answer posted here
 
A person is supposed to know about and already have solved this problem on one's own from the prompting given it in class on Tuesday 12/10/19. This two-page document is the very organized prompt on Page 1 and the answer on Page 2.
 
It leads to a higher level follow-up problem. How can you find the position where the speed is fastest in the orbit and also find the fastest speed in the orbit. An effort to set up energy conservation to solve this would be very good and is half the set up. Alone, it can't determine an answer. Alongside it, one has to set up angular momentum conservation.

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Assignment

This two-page document is an outstanding summary of last week. Use it before class starts on 12/10.
 
It instructs you to get four sets of answers. Each set is a quick list of energy types and their values. One of the four is done for you. You do the other three.
 
You are answering for quantities already solved twice last week. The answers for the things solved for were kinetic energy at the end of Path A to C, and then for kinetic energy at the of Path A to B to C, both on an inclined plane. These answers were 19.2 J and 12.8 J. The point of the attached review document is not to know those answers but to get them again by completely different-looking means, and to do it 4 quick times. So forget that you know these two answers and start the document now.

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Assignment

Helpful notes to clarity the lecture topics of Wednesday 12/4.
 
Think about whether Wednesday 12/4 was confusing.
 
Use this attachment to resolve it.
 
Then use the harder spring problems I handed out in class on 12/4.
 
It's important to do these things before Friday 12/6, at the very least this attachment.
 
Once all of the above is resolved, you can solve your Bungee Slider Experiment.

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Assignment

Unit 8 and 9 Conservation of Energy Required Tasks:
 
Study Guide - use as inventory list ASAP
 
Attached Challenge Problem: This is for staying current and caught up. It presumes that you know what U, potential energy, is. It works from a problem introduced already in Period 4.
 
The key to the Challenge Problem tells the story out of order a bit, so if it says something you don't think you're aware of yet, read it to the end in an effort for the gaps to get filled.

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Assignment

Review this ASAP - This would be bad knowledge to unlearn during a week off. This is the key to the item people were graded on on Thursday November 21.
 
Doing this one quick and easy = the road to simple discussion-free earning of points
Doing this one as if it's complicated = the road to failing the energy unit
 
Also, a graph needs to be made and brought for December 2 to be used in lab time. I'll post something soon that helps you check that graph.

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Assignment

Due December 2, as shown in class:
 
Knowledge of how to make the Wnet versus y graph that applies to your Diagonal Bungee Slider situation. Everyone was instructed to have this graph in hand (or on lap top) ready to be actively used during the labwork that commences right off the bat at 8 AM on Monday Dec. 2.
 
For those not ready to know their spring's k or their glider mass or their hill angle, we agreed that I would post a helpful thing so people could prepare using fake (bur reasonable) values of these three things. It was agreed those fake values would be:
 
k = 2 N/m for a spring that does obey Hooke's Law
Angle of 30 degrees
M = 100 grams
 
The two attached Excel files give you the chance to test your understanding of how to come ready with the proper Wnet versus x graph. Use them according to the following directions:
 
1) Open and examine the file named "Vertical Spring U Graph Maker." In it, you'll see how I made the graph used in the most recent Homework Check. This is a wise way to make a graph for any vertical spring in the presence of gravity. Look at the algorithm I used to program the column that obtains the values of Wnet. Study it. Do NOT open the other attached Excel file, "Diagonal Spring U Graph Maker - Sample Example" yet.
2) Considering the Wnet column algorithm in the file you already looked at, consider all the things that need to be modified in that algorithm so that it can properly calculate for the Hypothetical Givens that are: A hill angle of 30 degrees, A mass of 100 grams, and a spring that DOES obey Hooke's Law with k = 2 N/m.
3) Still without opening the "Diagonal Spring U Graph Maker - Sample Example" attachment, reprogram the Wnet file so that it properly programs the Hypothetical Givens just mentioned. You should end up with a parabolic Wnet graph that would be useful to bring to a lab where a person had a 100 gram glider on a 2 N/m spring, on an air track set at a 30 degree angle.
4) Once you've committed to your Wnet programming equation, open up the file "Diagonal Spring U Graph Maker - Sample Example" and see if you did yours correctly. And see if I made any mistakes in how I did mine.
5) If you are able to, it's smart to bring task #3 above done on a laptop that you can bring to class. That way, once you know the real life classroom k, M, and angle, all you have to do is put those new numbers in the spreadsheet and see the graph automatically change.
 
Either way, your job is to come to class on December 2 prepared at 8 AM.

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Assignment

People who want to know EXACTLY what's going on with Tuesday's vertical spring Problem:
 
Work through the attachment called "Bungee Plunger..." before Thursday 11/21. It may seem like 6 pages, but that misses the point. It's very efficient. It's mostly 1 page which establishes exactly what was to have happened in class on Tuesday. If Tuesday went wrong or was unclear, this page will not be unclear. The first page of the document establishes a practice problem, you solve it, then you check the answer. Pages 2, 3, and 4 are all devoted to checking the answer in a meaningful way, with Page 3 being entirely taken up by a good graph.
 
Once that goes well, you will want to test yourself again. So the bottom of Page 4 says, "Here are two more, try these." Then Page 5 is devoted to the answer to Problem 2. And Page 6 is devoted to the answer to Problem 3. This document establishes the language and vocabulary that is to be unleashed in any energy budgeting problem, and that is vital stuff.
 
The other attachment: This is what the actual Bungee Glider on the Diagonal Surface Experiment will look like. You should see this as excellent information to have, because you can now work ahead by comparing the Diagonal Bungee Glider document to the "Bungee Plunger..." document that you just got to know for practice. You don't have to work ahead, but it's wise to when you have time. Enjoy.
 
You will see terminology used in the Diagonal Bungee Glider document that we have not gotten to yet. That is perfectly fine. Not to worry. I'm showing where we are headed. (For example, it uses something called Change Of Potential Energy in the place of work.)
 
Loud and Clear: to be caught up, you have to know how to do the problem on Page 1 of "Bungee Plunger..." before Thursday, November 21, 2019. I claim that between the lab time (on Tuesday) and the "Bungee Plunger..." document attached here, I have supported you well in meeting that goal.

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Assignment

Please know this attachment ahead of Tuesday, November 19 to be ready for Tuesday, November 19
 
 
In case the following detail eluded you from class (because I had you do the proofs), it's now considered common knowledge from successful proofs on 11/15 that the following is reliable:
 
Wnet = [        ] - (         )
 
Where [         ]  is the instantaneous value of the quantity (0.5)M*v*v where v is final v
 
and
 
Where (        ) is the instantaneous value of the quantity (0.5)M*v*v where v is initial v
 
And the beauty of it is that neither force nor acceleration have to be constant for the theorem to be true. The theorem is the Work-Energy Theorem, and people have to willing to use it from now on in order to be eligible for an A in the class. The attachment picks up as if the Work-Energy Theorem is common knowledge.

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Assignment

Solution in detail - Problem 1, Newton's Laws Test
 
Lower than 7 of 10 scored on Number 1 is C-level work at best and rightfully so. This solution states precisely what's written to guarantee 7 of 10, and it's 3-weeks-old basic facts that take 2 minutes to write, and to not proceed to write it clearly represents a choice, a decision to not be in the class. End

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Assignment

HW due Friday 11/15
 
5 points, extremely quick, precisely as I stated in class. This attached document removes any ambiguity whatsoever. It should take 15 minutes to do the bare minimum, which is only Page 1 of this two-page document. Only Page 1 matches what I said in class that you have to do, and I'm not changing that. Page 1's answers for final credit are only symbolic expressions, and the Page 1 instructions state precisely how to format these answer expressions.
 
Because this assignment is so short, I figured certain people will want to work ahead. That's what Page 2 is for. Reading Chapter 7 would be relevant.

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Assignment

Update: This message got more specific information added to it on Sunday 11/10 at 9:48 AM. It's content is not changed, and the attachment is changed in no way. But the words in the public notice were refined and made a bit more specific, especially about what precise subset of the test is graded so far.
 
Newton's Laws Test Key
Note: I improved the attached key at 7:40 PM on Friday, Nov. 8. So if you downloaded a copy before that, replace it with this better one.
 
By design, there might be a chance or two on Wednesday November 13 to earn a few more points on this past test whose partial key and rubric is attached. Don't try to plan ahead or study for that. It'll be fair and good. Reading the attached key will help. I have some things structured so the test can help you learn and not just be an evaluation tool. The idea is to not fret over mistakes made in execution in cases where the strategy chosen in solving was the right strategy. People SHOULD fret if they are not aware of certain basic facts, like what to do with the fluid resistance problem. (Not Following Directions if that's the case; it has nothing to do with being in advanced physics. I will write the acronym NFD for Not Following Directions on certain papers to which it applies.) You'll see a grade in the gradebook this weekend that is the grade for the portion of the test that I will grade this weekend. This will be a subset of the full 24 points. The full 24 points won't be determined until November 13, and it is wise to consider why this is so. Graded on the weekend will be:
 
A part of Problem 1, but you won't see that score yet.
All of #2 for 3 points (visible in gradebook), and not knowing #2 amounts to Not Following Directions.
For #3, 4 of 5 possible points will be graded and the amount earned of those 4 will be visible.
For #5, 5 of 6 possible points will be graded and the amount earned of those 5 will be visible.
 
In the list above, confirm that the graded part I make visible prior to November 13 is 12 of the 24 points.
 
The missing 1 point mentioned in #3 above has to do with the fact that 1 point is linked to the HW that is due on Wednesday, November 13. Follow directions, and it won't be a big deal.
 
Using this attached test key affects other near-future credited activities (in at least 3 ways) and should be absorbed sooner rather than later. By design, not every answer is given in the key, and that has something to do with what I put in the long paragraph above.
 
Also, there is another posting present on the weekend between 11/8/19 and 11/13/19 about what to do for the Work Homework. The HW is as explained in class, but most people will need to see that other posting and attachment for that homework to be step-by-step simple. Don't talk about it. Read it, and do it. Follow directions.

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Assignment

Update: It is Sunday 11/10 at 12:10 PM. I have newly edited the document "W Integral Example", and it is now attached. It makes the HW due Wed 11/13 step-by-step simple when its instructions are followed. By following the directions, I say this takes an hour. Do not talk to anyone about it. Do it. See me directly if an instruction isn't step-by-step simple. Why do you think I so carefully edited the document.
 
Due Wed. Nov. 13: The Work Integral Homework as instructed in this document (which matches what I said in class), both Parts 1 and 2. Write the results neatly as I instruct and on easy-to-read paper that is not this document. (And it is NOT my job to say that.) As it's not my job to say to number the results clearly. I'm not crediting anything that's not quick to grade. Show work where required. The document makes it clear where those things are. Obviously, for all numerical proofs, work-showing is the required standard, but there is one exception to that, and it will be clear why that is an exception if you read the document.
 
People assigned 37 degree or 53 degree angles. Do NOT use the calculator for sines and cosines. sin(37degrees) = 0.6, cos(37degrees) = 0.8, sin(53degrees) = 0.8, cos(53degrees) = 0.6. Use only these, to one digit. Stop the calculator complication nonsense.
 
For anyone who forgot their individually assigned constants (mu and theta from the test), the attached spreadsheet has them again.
 
The Work HW is in two parts. The attached document has them laid out clearly and efficiently. The two parts are:
 
1) The integral problem that involved exponential decay of velocity that I described in class on Friday Nov. 8.
 
2) This is all in the attached document, so you don't need to read what's below, but anyway...You start by redoing the acceleration calculation that I assigned you on #3 of the Newton's Laws Test. You don't have to show much work for that. Just state the acceleration, and be accurate. Use the angle and the mu value that I assigned to you specifically. We will continue to use a 20 m hillside. We will call it a 2 kg mass. I will change the starting speed to 10 m/s.  You will use the acceleration and the starting speed to determine the instantaneous speed for the end of the 20 m displacement. Then I will have a simple list of quantities for you to evaluate from your quick calculations above. It will be these quantities:
 
A) I will tell you to multiply the friction force by the 20 m. This will be the dot product of the friction and the displacement. It will be a negative dot product.
B) I will tell you to multiply Mgsin(theta) times the 20 m. This will be the dot product of the Mg and the displacement. It will be a positive dot product.
C) I will tell you to take the square of the initial speed and multiply that by M and by one-half. This will come out to 100 J, and you can check that yourself.
D) I will tell you to take the square of the final speed you calculated and multiply that squared speed by M and by one-half. I don't have that answer for you.
E) And after all that, I will tell you to look at Answers A, B, C, and D all together and see if you can recognize a budget.

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Assignment

Very good Newton's 2nd Law Test status:
 
1) Nobody missed it. That is great. That puts a person in a position to use it to learn no matter how many points they earned. As an added bonus, being present for it increases the chances to earn higher credit on some other things. One of these things is connected to the HW due on the 13th.
 
2) Each individual should be able to tell the difference between Not Following Direction Errors and Execution Errors. An example of an execution error is choosing the more difficult coordinate system to use in a Newton's 2nd law structure. A Not Following Directions Error has been explained elsewhere and should never happen, and I do write NFD on those papers. I have no right to say anything critical about Execution Errors and my opinion is that a person should not judge themselves as having done "badly" on a test if they have execution errors*. (But in those cases, use the test to get better at executing.) NFD, on the other hand, is a screw-up. (*So you won't see me writing a speculative EE on a person's test.)
 
3) The score on the first graded 12 points has now been put in the gradebook for each student and is visible to students. A strong claim is made now and defended by the attached document: 9 points of those 12 are guaranteed by just following directions. See the attachment. A person earning less than 9 is choosing not to follow directions in at least one place. There were many 9's on this, and a 10, and an 11, and a 12.

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Assignment

Lab write-up template that you may steal from me. You can download it, cut out the irrelevant content and insert your unique content for any experiment you do if you like.

Due:

Assignment

Final Unit Practice Loose Ends before the Newton's Laws Test of Friday, Nov. 9:
 
First attachment is a key to one of the quick practice diagnostics made available on Wed. Nov. 6. It's here. Time wasn't made to do this practice diagnostic. Most people just took it home. It was one page. It says "20 minutes" on the top line, but I said that for where this class is, it should be 10 minutes.
 
The key is attached, and the original question document is attached right now.
 
Reminder: Newton's Laws Test Friday. Any FBD scenario: something inclined plane-ish that involves interacting masses, something circular motion, fluid resistance is fair game.
 
Hemisphere of Ice Problem:
Mastery-level question posed in class having to do with how high off the ground the square loses contact with the ice. To break that down into simpler Newton's-Law-Based pieces, do it as phrased in this attachment. Page 2 has the answers. I'd like to NOT post step-by-step solution lines. You're now where you want to be doing that without my input. Do your own solution, compare to the answers on Page 2 and bring very specific questions if yours don't match up.
 
I think that's it. If I do think of any other minor loose-end posting, I'd do it before 3 PM on Thursday, but it's probably not going to happen.

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Assignment

Full rubric of the 10-minute mock test from class of Monday 11/4
 
It ended up being 13 points actually. Document is efficient. The test prompt is 1 page, and a thorough, yet brief, solution with rubric is 2 pages.
 
Also, here are two lists of Topic Objectives for this unit. Run through these as inventory checklists to see if you know exactly what's referred to by each skill and fact on the Objectives List. There are two, because this is Chapters 5 and 6. Have you read those chapters yet?

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Assignment

NEW! Updated! This posting had a file added to it at 6:28 on Sunday 11/3. The addition of this file does not require any new work for anybody. Those who already did this HW before now will have nothing new to do and will know why my adding the file could be of value. They may judge for themselves.
 
HW DUE Monday 11/4: Worksheet 6.3 establishes the problem whose solution is due, as explained in class. I'll be checking. You could solve what I said to solve in class without this WS 6.3 document. But the attached document walks one through the steps.
 
Now, MORE IMPORTANT THAN 6.3 is the other document, "Resistance ODE Summary". 6.3 introduces the topic, but honestly, it's just a repeat of what's derived in the textbook. I am far more interested in what's in the other document, which is called "Resistance ODE Summary."
 
Get the main idea of 6.3 and know that it tells you the expression you are trying to prove. If you fail to prove that expression, move on anyway, PRETENDING THAT YOU HAVE successfully proven it. And then go to "Resistance ODE Summary." It's far more powerful for my course.
 
For example, if you were to sink all your time into doing some u-sub integral, which is what some people do when they're stuck in JUST THE MATH part of 6.3, you'd be missing the whole point.
 
If you were to sink all your time manipulating some ln(A/B) expressions during 6.3, you'd be missing the whole point. You'll notice you are supported below in order to avoid this.
 
The Whole Point is driven home in "Resistance ODE Summary." So try to get the math smoothly in both documents. But if the math of 6.3 has you stuck, move on and get the big picture through "Resistance ODE Summary."
 
NEW: A one-page file is now attached that shows exactly how the math of WS 6.3 should go. This is posted now with the intention that people tried the math on their own before looking at this one-page math trick that is named "Fric Prop v - Here's How the Math Goes." The addition of this document should in no way change the physics of what was studied.
 
The reason there is a deadline is that it's vitally important that you get exposed to the main idea of this topic BEFORE Monday, November 4.
 
And remember, the textbook in Chapter 6 does the problem as well. It's a good source.

Due:

Assignment

Study this chart layout and its graphs.

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Assignment

-UPDATED!-
 
The "Proper" order of topics for Chapters 5 and 6:
 
Pay attention carefully, because the lab-based way things happen in Period 4 means that sometimes certain ideas during Period 4 come "out of order". In the event where this causes confusion, my Solution Notes documents and postings like this are designed to repair that. So regarding Free-Body-Diagrams and Applying Newton's 2nd Law in Circular Motion Situations, here is the order of things when you are pulling it all together outside of Period 4:
 
1) "Class Notes on Turning Vehicles" - This is stuff that was said in class, but was never handed out as paper notes. At home, start with this. This document shows the simple set-up of the turning vehicle (moving in circular motion) that CAN turn on a flat surface because of friction. And then it goes to the turning vehicle that can go around the circle WITHOUT FRICTION, because the road is an embankment. (If you're clever, you say, "Without friction? Then tires can't grip the road!" Right. So the document says in the banked turn part to just pretend the car is sliding like an ice block with stationary wheels. It's fine, because this part is frictionless. Keep it simple.) This document is parallel to Chapter 6 in the text. I should show the rest of the solution for how fast I would have been going when the police officer stopped me, and when I get a chance, I will.
 
2) Next you go to "Banked Curve, with Friction, Mastery of UCM Applications" - This is the green one I handed out as hard copy on Friday, October 25. If your name is Wood, Park, Velazquez, Welcher, or Magid, you did not receive this hardcopy. So it's attached here as a word document. (It won't be green though.) HOWEVER, there are a few things I wanted to point out in person about this document but didn't get a chance to on Friday, October 25. So please, whether you got the green hard copy handed to you or you just downloaded it from this attachment, could you please also consult the pdf attachment to this message. This pdf is a scan of the "Banked Curve, with Friction, Mastery of UCM Applications" document, but with some hand-written Heads-Up comments on it, hand-written by me. These are the things I wanted to tell everyone in class.
 
3) The skill of choosing coordinate systems - sometime during the weekend of October 26, I attached  a very useful additional handout in this message about the skill of choosing coordinate systems in these types of solutions. It uses the same situations as the documents mentioned in #1 and #2 above. And it illustrates the skill of choosing coordinate system the easy way versus the hard way. I have added the tag "UPDATED" to the top line of this message.
 
4) Supplementary Problems (SP's) - Brand New. These are if you're working ahead. They'll be helpful when doing test review. I'll announce test date and general calendar in another posting.
 
If you were to work on nothing more than the circular motion applications in #1 through #3 above, the Flying Pig, and read Chapter 6 between now and Tuesday October 29, you would be so nicely caught up! Calendar and test day to be posted soon. Roughly Nov. 4 or 6 will be test day.

Due:

Assignment

Extremely Urgent:
 
For all whose Free-Body-Diagram homework comprehension document continues to be red-stamped:
 
Attachment

Due:

Assignment

BIG SOLVING DOCUMENT:
 
One might be in danger of thinking, "Hey, in Warren's class, he keeps talking about theory, but when's he gonna bust out the math skills that show some efficiency in solving a problem from start to finish and gets the right final answer." *
 
Well, I DO do that. I might not always do it from start to finish at the board in front of you, but when it's necessary, you know I put it in writing in my guided solving notes documents. (You know: the ones that discuss solution steps, with blanks to fill in.)
 
For the rotating platform, I gave a two-pager in class today that gets anyone started on the problem. It was kept to two-pages so that some can see if they could finish the whole setup WITHOUT my interference (which should be the goal.) And I also said, "These first two pages are part of a longer document that's 5 pages." I said I'd post that, and people could then decide how much of it they want to do on their own versus how much they want to see me do it. You have to read the document and do it in the order I intended to recognize the distinction I'm talking about.
 
My "seeing teacher do it" option even includes algebra efficiency advice in writing. I reach for the calculator as little as I possibly can.
 
Anyway, enjoy the Rotation Platform Lesson Guidance Sheet (attached and as described above.) It needs to be seen as required information of the class. It IS the lesson. Being caught up means understanding the rotating platform problem by Friday 10/25.
 
*Another thing about showing versus not showing algebraic use of Newton's Laws: It's a waste of time to stress any algebraic use of physics if one person in the conversation does not agree with the way forces are defined. People with red stamps on Free-Body Diagrams don't agree with the way forces are defined. Doing algebra with those people would hurt them. They'd be building on a foundation that will collapse.

Due:

Assignment

FBD HW Grade Document Key 2019
 
Urgent: (As of Monday 10/21)
(Urgent for only two-thirds of the population, actually.) A person who didn't get 100% on this, answering the questions in about a minute, is a person who chooses impossibility, because they won't adjust their vocabulary. No matter how many different ways they are shown that force is ENTIRELY about agent and victim, they won't accept it. If that remains the case, they can't do Newtonian physics.
 
But the fact that one-third of the class IS accepting these definitions and is keeping things very simple proves that this information is entirely accessible if the person stops expecting complication and makes adjusted vocabulary a part of their usage.
 
I don't recommend conversations with other students to change this at this point. (People have done that.) I recommend reading.
 
Notice I refer to the document's items as QUESTIONS and not problems. This means the items ask for definitional facts, not mathematical things to be proven. That's supposed to be obvious by now as the central element of the free-body-diagram process. The practice documents have repeatedly pointed out that no math is considered when a free-body-diagram is built. These questions only ask about what forces belong and what they represent physically, as promised.

Due:

Assignment

Key for the FBD-understanding-check that was offered on 10/17/19 is attached. To see the original questions, you may look at the attached word file. To see the key, you go to page 2 of that same file. Don't read the answers until you have seen and tried the questions for yourself in 10 minutes or less.
 
Those who got 100% may use it as their grade on this. Everyone else, the credit is unresolved; for you, this ended up just being practice. Since you tried this early, we don't want to credit anything but 100% on this topic. We'll take care of the real score on Monday 10/21 with some other paper that everyone will answer for credit. Well, all but 4 people. 4 people got 100% on the attached items. To earn 100%, you have to name the agent of the force in Question #5.
 
Reminder: the goal was to Master Free-body Diagrams By The End Of The Week That Is 10/14 through 10/18.

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Assignment

I mentioned in class the need to execute a self-testing regimen on the Free-Body Diagramming skill, and that we need it done by the end of the week. I said I would post many things to support that. That is what this posting is. For these things to have value, most of it needs to be accessed before the class of Thursday, October 17, because if something isn't going well, via miscommunication by me, I will need to hear that from you by Thursday, so that I can fix it. But I can't fix it if students don't tell me. And students can't tell me if they don't access what I post for them. Also, only some attachments are to be used by Thursday. The instructions below tell you the exact order for the use of my attachments.
 
The following has to be done in order:
1) Efficiently read Newton's Laws on Pages 100-109 of the book, most importantly Newton's 3rd Law.
2) Get my Three Resource Documents: "AP-FORCE DEF", "Perfect FBD Strategies", and "The VI Method". These are the heart of the unit's content. Expect them to always be nearby as a resource while you are getting to know the Chapter 5 and 6 problem techniques. They should be consulted repeatedly throughout the applications below.
3) Applications in the following order:
A) Chapter 5 - Problem 54. You first read the problem statement document only. Before doing any kind of mathematics, you make three separate FBD's on your own BEFORE consulting any other document. Only when you've committed to your 3 separate FBD's, you then open the document named "Perfect FBD's for Chap 5 #54..." to assess what you did. There is a lot of content in this document.
B) Use the file "Concrete Example of the VI Method". The VI Method will solve anything. But only if the FBD-making skill is perfectly intact. And this week is mostly about the FBD-making skill. Which means...
 
We Now Test Ourselves:
First, use the document "Quiz Purely on FBD's." Treat it like it's a quiz where you only have 10 min.
Second, open that quiz's key. See what vocabulary you had missing. Heightened awareness.
Third, use the document "Quiz Purely on FBD's."
Fourth, use that document's key to self-assess again.
 
So that might be enough for now, but consider the following:
 
We start to realize that these topics can be rabbit holes where we can make up more and more variations, and you might notice that my "Quiz Purely on FBD's..." series continues on and on with more documents. But I certainly don't think you have time for them all at home in one week. The ones mentioned up till now (and #54) are focused on the Free-Body-Diagramming skill, which I said is the goal for the week. Perhaps we've met that goal with the training mentioned above. Maybe you're done, and it's simply time to bring questions to class.
 
However, if you do have time to spare, and you're making good progress, you'll see that I have a few more attachments in this message. But only spend that kind of extra time training if things are going well. Your choice. Careful: The one working-ahead document called "Quiz Purely on FBD's - Numerical Solving" requires a bit of knowledge I haven't gotten to in class yet. This is the idea that scales cannot depict that value of weight.

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Important HW Due Tuesday October 15 Upon Arrival
 
Either do the Introductory Tutorial 1 or do the Tutorial 2, which assumes prior experience. One or the other is due. Both are attached.
 
Tutorial 2 contains the self-correcting resources that I said I would give to those I gave a prior knowledge quiz to in class on Friday, October 11. This prior knowledge quiz was only given to those who took a year of physics prior to this.
 
IT IS EXTREMELY IMPORTANT TO DO TUTORIAL 2 IN THE ORDER IN WHICH I WROTE IT. Do not peak to later pages and their diagrams until you have followed all directions on the earlier pages. It's important not to see certain later given diagrams prematurely.

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AP Exam Signup Codes:
 
AP Physics 1: MQRMN7
AP Physics 2: MVZQRR
AP Physics C Mech: RG9Y6A
AP Physics C E&M: 9GA2J4
 
Students in my Periods 2, 4, and 5:
Please sign up for your respective AP Exam Platform ASAP!

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Do this as a part of dialing in Test Practice. It's the beautifully written version of the Advanced Problem from the front board of the class of Friday, October 4, 2019. I had been referring to this as the Jerk Problem.
 
UPDATED: Final completion of the key in the document was completed and the refined document was reposted at 4:18 PM on Saturday, October 5. So if you got one before that, your key is incomplete. But the rest was accurate.

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Two-Dimensional Kinematics Test is Friday, October 4.
 
The attached document here is very high quality in covering about 60% of main ideas that are on that test. Do this practice item ASAP. I estimate it as a half-hour thing. I'll add an answer Page later or in class on Thursday 9/26.

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4.0 Packet that's due at 8 AM on Tuesday 9/24 (as mentioned in class) is attached here!
 
Print the packet and complete what it says to. I'm also going to check understanding in class with a single in-class question to answer.
 
You only have to do Pages 1 through 6, but many people choose to do more...and we encourage that.
 
I have called Pages 1 through 6 the 15 Pieces of Flare. But this packet can be done all the way up to 37 Pieces of Flare if you choose. Here's the link from which that reference comes, a 20-year-old classic:
 
 
And I was going to fix the typo, but I think I'll leave it in, because I consider it to my credit that I misspelled the word "flair."

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Reminder: Taking derivatives quiz is happening on Monday 9/16. This quiz will have 5 given functions and you tell me the function's first derivative. It will be expected that you answer these with your Quick Calculus book open to the Cheat Page, Page 254-255.
 
Also, the answer to the question from the 3.0 Packet from class: the question was at what time will the mass return to its starting location. The answer to that question is 6.36 s.

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Document to Help You Complete Experiment 1 - Picket Fence Version
 
This repeats the 3 (or 4 with 4th being optional) tasks that I wrote on the board as the assigned Experiment 1 tasks. Here they are very nicely written and organized.
 
*The helpful document has now been re-uploaded with some answers given so that a student can check their progress.
 
Your Experiment 1 answers don't have to be complete and fully done error-free when you arrive to class on Tuesday 9/10. We had only asked on 9/6 that you try to get the answers and that I'd answer questions about them on 9/10. September 10 from 8 to 8:30 will be the last Period 5 time to ask such questions about this first experiment. (I'll answer your questions about any topic anytime you ask, of course. I'm just doing my best here to communicate the schedule I'm keeping to and what you need to stay caught up with.)