Some necessary information for Semester 2: In the attachment that's the key to FR2. See it before Tuesday 1/23, because it does affect the first graded thing in Semester 2. Seeing the attached key is a form of HW. I'm not grading anything on 1/23, but I am on 1/25, and the key to FR2 provides important background knowledge that makes the first thing in Semester 2 familiar.

 

A healthy way to understand the final: Don't let anyone tell you how you should have scored on Free Response 1 and Free Response 3. Notice I haven't done that. It's none of my business. However, what is my business is to point out that you ARE supposed to write a relevant concept down on each item in FR1 and FR3, leaving nothing blank, because the concepts stressed were the heart of the course. But still, your willingness to do that - by listening in class and finally realizing that a test is a communication device about relevant concepts - that willingness is your decision. I will not comment on scores on FR1 or FR3.

 

FR2 is entirely different. I AM directly criticizing the act of not scoring most of the points on that. My reasons for this are well-defended, and if you don't know what those reasons are, then you must pay attention to the Public Service Announcement that I put in the attached key for FR2. And there is only one reason why I'm talking about it now at great length: It's to deliver information about Semester 2. People unaware that Free Response 2 on the final was TELEGRAPHED IN ADVANCE are going to have a problem right off the bat in semester 2 if they don't make an adjustment. Everyone needs to read this solution. (Those who didn't blow it on FR2, reading the key won't be a waste of your time, because I mention some alternative solution views.) Anyone who blew it on Free Response 2 needs to face the sobering reality that I point out in the key in the form of what I call the Public Service Announcement. The urgency of this PSA is that this type of differential equation problem isn't going away and is only going to become more central in the course. It was covered no fewer than three times in Semester 1.

 

Last healthy ideas about understanding an AP exam: The final was designed for people to have a predictable time scoring on the Free Responses. On the other hand, the multiple choice isn't supposed to be predictable. A score on it of 22 and up out of 32 is in the common 5 percentage zones in typical years. Nobody would ever be criticized for getting Multiple Choice questions wrong. The national scale is generous. It rewards quality of knowledge, concept application. I as a student never saw roughly the last 13 multiple choice questions on the AP exam I took. Aside from the fact that I wanted to see them because I liked physics, it wasn't a problem, because I did have good quality thinking on the ones I did answer. The national curve rewards that.

 

The in-class test ended up being out of 73 instead of 75. The key to FR2 explains why. It's fairly minor (but annoying to me). You don't need to worry about it, but there is physics to learn in the reason why, so please read it.

 

Based on 73, the AP score cutoffs are as follows:

 

On the national scale the year this test was given, the lowest 5 was 53 of 90. Percentagewise, this is 42.99 out of 73. That makes the cutoff score 43 on the final for a 5.

 

On the national scale, the lowest 4 was 42 of 90. Percentagewise, this is 34.07 out of 73. That makes the cutoff score 35 on the final for a 4. It will not be 34. I announced in December that these generous 3, 4, and 5 scores would be cutoffs and not rounded values. A 4 score must be no lower than 46.67%, AKA 34.07 out of 73. The score of 34 does not exceed that threshold. 35 is the lowest 4.

 

On the national scale, the lowest 3 was 33 of 90. Percentagewise, this is 26.77 out of 73. That makes the cutoff score 27 on the final for a 3.

 

To yet again point out one of the several ways that I telegraphed FR2 in advance, I am yet again attaching the notes called Resistance ODE Summary. Still needed for Semester 2.

 

FR1 and FR3 Solutions from the Final:

 

You have them. I've said for a long time now, go to this site:

 

 

FR1 was from the test of 2017, number 1.

FR3 was from the test of 1999, number 3.

 

You go to that year and find Scoring Guidelines to open the rubric.

 

By the way, about my posting for the solution to FR2. I'm not making any claims that "the class" did bad or good on the final. Any statement in the FR2 solution document that I made about score cutoffs or the consequences of bad FR2 preparation are statements that I've made before correcting anything. I don't know the class averages. The statements I made in the FR2 solution document are objective statements though.

 

But I do know that class was set up so that 100% of students are supposed to be familiar with FR2 and score well on that page. And I do know that not 100% of students looked at what I told them to look at to prepare for FR 2. (I know this by glancing at a few papers.) So I can say factually that this will be a problem for certain people heading in Semester 2, where differential equations will take a more central role. That's why I make the Public Service Announcement in the FR2 key.

 

I claim: follow my directions from class and a person knows FR2 well. I don't make the same claim about FR1 and FR3. On those you have to apply general principles to a less telegraphed problem. Your adaptation to that is your business. All I can do is teach the principles that you use as tools. I intend no commentary about how people score on FR1 and FR3.

 

But FR2 I telegraphed in advance many times.

 

And finally, speaking of not having FR1 and FR3 telegraphed in advance, people should have noticed by now that I sometimes intentionally rip problems for tests from this site. It's not supposed to be news by now:

 

https://apcentral.collegeboard.org/courses/ap-physics-c-mechanics/exam?course=ap-physics-c-mechanics"

  

Be ready to spend class time on physics principles as they relate to Semester 2. Conversations about what a trick it was to know something on the test will be shut down. No time for unfounded claims. It'll go without saying that all tested items had been accessible information.

Big Practice Document on the Fluid Resistance Topic, which is the topic of the second Free Response (FR) problem on the final (which I've been saying for a month now.)

 

Let me remind you that Resistance ODE Summary is very thorough. You should review it again. And now. When that's done, here's an opportunity to see if you came away with strong enough language to adapt to what I asked on the 2015 FR2 problem. When this was asked in 2015, a lot of people earned 100% on it, or close to that, and a lot of people earned like 3/15 on it, with very few grades in the middle. The key talks about that.

 

The key was a discussion with people in 2015. But as it's posted here, I break in a couple times and say, "hey if you're reading this in 2018..."

 

The final statements in the key talk about what people are to expect in Semester 2. That was written as a notice to people in 2015, and it's neither negative nor positive. The principles are the same now, but I didn't specifically write the end bullet points for the 2018 students. I did, however, leave them in the key document, because it's stuff that's useful for you to know: things about what a person's mindset should be when approaching tests.

Many excellent rotation tests. Lots of good preparation.

 

The third FR on the final is going to be this very same topic, so prep and review for that the same way.

 

And the second FR is going to be about Separation of Variables and motion through resistive medium. So prepare to be solid on a big chunk of the final.

 

I have a very busy weekend of work, but if I have time, I'll post a typed form of the rotation test rubric.

Important Reminders for Rotation and the Final Exam:

 

It was agreed that I'd devote time to go over the 1993 Multiple Choice Mechanics Sample Final on Friday, January 12, and the only way to make that happen is that a person must sit for 45 uninterrupted minutes at home between now and Friday and take the 1993 exam like it's a real test. (That means at a desk, with scratch paper for solving, and all that.) Then when you're done, use the key and see how many you got right. If you left some questions unanswered in the 45 minutes, and then want to take more time to do some of them before looking at their answers, that's up to you. This mock-testing and answer-correcting procedure has to happen individually before 8 AM on Friday. DO NOT SIT AND DO THE TEST IN STUDY GROUPS AS YOUR FIRST RUN-THROUGH OF SUCH A TEST. That defeats the purpose. You have plenty of other problems for that.

 

People who show up on Friday as if they will do the 45 minute mock test sitting in my classroom during Period 4 will not be catered to. I'm not devoting those 45 minutes of class time. I'll be set up to show best solutions methods (with efficiency being one goal) of the things that people say they want seen from already having been through them at home. When 1993 is exhausted, people can move onto other years if they want to.

 

I posted the 1993 exam (with all the others and their keys) awhile ago, and here it is attached again. And its key. Do it like a test as if it counted. Moving on...

 

The last useful rotation solution page I made for you is called Cranking Out The Compound Pendulum Collision Answer. You've had access to that for awhile as well. It comes after Notes Part 6. I instructed people to go through that problem now as the document presents it, and I showed the visual in class today. I did just find and correct one typo in it (an exponent of 2 I forgot to write), so I'm re-attaching the document here, corrected. I also refined some of the explanations, but briefly. The document is improved. It's the highest level problem I have in rotation.

 

The Derivatives Quiz from ancient days is being re-offered this Friday at lunch. So anyone who wants to may come and take another Derivative Quiz, and people will get to keep the higher of their two grades on the two quizzes. The given functions will be different, but will involve similar decision-making.

 

Aside from Mock Final Exam questions you want to bring up, the remainder of the semester is tying lab loose ends, and we'll also have the rotation quiz at 8 AM Friday, and that will end within 20 minutes.

 

I don't have any new concepts to highlight unless you want me to address the Parallel Axis Theorem (for calculating moments of inertia) in person. If you don't ask for that, it means you let the textbook take care of it, which is crystal clear. But you do have to know the Parallel Axis Theorem.

 

And finally, I made yet another mistake. I spoke loosely when I said "Smells Like Teen Spirit", yet I know that's from 1991 and not 1993. I should have said "Heat-shaped Box."

Check Your Comprehension of Monday's Class - UPDATED THE NIGHT OF 1/18: "Proofs of Energy Methods in Rotation" is a document I made to help you do that, and I posted this new document the night of 1/18. There were theoretical proofs connected to the nuts and bolts of solving, and you need to make sure you got the main punchlines of such proofs.

 

The thing on the board called "Proof of Why the Two Cat Methods are the Same" is a very big deal, and I had left you to fill it in. If you didn't, or did it wrong, you missed the point. Not many people asked about it. That could either be good or bad. The document "Proofs of Energy Methods" states again what those blanks were to fill in and why they mattered.

 

I've attached the speed answers to 12.1 (with a GREAT Star Wars reference). Make sure you do WS 12.1 on your own before looking at those answers. I explained in class the specific way you'll be graded on 12.1 as HW. The original WS 12.1 document was sent in December.

 

The grading technique of HW 12.1 (Rolling Things) will be linked to the Rotation Quiz that occurs on Wednesday. That quiz has been listed on the Study Guide, and be aware that I have stuck with the Study Guide. With that in mind, I've now covered and shown examples of all the types of problems that are reinforced by Problems 1 through 11 from the Supplementary Problem sheet. Last week through now are the times when I should be seeing people coming to me specifically with questions on those 11 problems. If not, it means, you're setting them up yourself and working to the final listed answers (in brackets at the end of each problem) successfully. And you'd be used to such techniques during testing. Maybe I'll have time to post even more solution notes to some of them like I have, but I'm not sure if I will. You should be coming to me if you need to. Unit 12 SP's are attached here again, because why not?

 

The end of "Proofs of Energy Methods in Rotation" includes a typed version of what's in the handwritten Mallet Problem alternative methods that I handed out today. Note: in the Mallet Problem, the handle's mass has always been (0.5)M. In class today I labeled the handle mass's wrong in a hand-written handout diagram. All algebraic answers have been consistent with the handle's mass being (0.5)M, and the original Mallet Sheet had (0.5)M as the mass. Nothing has changed, even though I originally labeled it wrong on the handwritten document. Change the handwritten document if it doesn't say (0.5)M.

 

Attached is a reposting of the original Mallet Problem but with Answers to 1 and 2 at the bottom of the page. Just in case anyone was ever unclear about what its final answers were supposed to be. This might be overkill, but I want one of its answers loudly stated since some of the learning depends on getting that same answer but from a different point of view (in the last few lines of "Proofs of Energy Methods in Rotation".)

 

I've attached the answers to today's 5-question Homework check. "Readiing Check Answers..."

 

Notes Part 6: Do them now if you haven't. They're great. They finish the unit, and thanks to Liam being the Human Gyroscope, you know enough about angular momentum to tear through Notes Part 6 now. They very carefully help with SP-14 actually. I just re-read them, and I really like them. A Mr. Warren of the past did well writing them. If you disagree, tell Mr. Warren of the present. I re-attached Notes Part 6 here for a dumb reason: the ones I posted for you before say "Part 5" in the title even though the file name is Part 6. Part 6 is correct, and the title in the file is now corrected, so if you haven't already printed them, there you go.

Rotation Unit Test - Wednesday, January 10 - We are on schedule with one exception - I wanted to touch on Notes Part 6 before the end of class on January 4. I'm ambitious.

 

This posting of rotation Unit Documents have been here since mid-December. This entire posting is not new. I'm just bumping it up as a reminder.

 

MISTAKE CORRECTION: Since mid-December, the file called Unit 12 Solving Strategies has been in your possession. It's a great, informative file. But as of 9 PM on 1/6, I have corrected two mistakes in it: when in error, it referenced "Rotation Notes Part 4". That should have said "Rotation Notes Part 5". It's now corrected. Also, when in error, it referenced "Rotation Notes Part 5" in an effort to give advice on SP's 12 through 16. It should have said "Rotation Notes Part 6" there. That too is now corrected. (What happened was I made my notes a little better and renumbered some this year.) The corrected Unit 12 Solving Strategies is now attached here, as of 9 PM, 1/6.

 

Notice as of Saturday 1/6: Everything after this paragraph was posted mid-December. I'm reminding you on Saturday 1/6, you need to have worked through my notes at least through Parts 5 and 5A by now, and ideally you should be finishing all of my notes through Part 6. (If I write them and give them, it always goes without saying that you become aware of their contents as soon as possible.) I've covered in class the ideas that are handled in Notes 5 and 5A. It's always your job to know what things are in the notes so that YOU can be the most intelligent person about when to use them. For example, by being aware of what's in 5 and 5A (torque), since I gave them early, you then know that their topics (torque) came up big in class, and through that, you were signaled that you're behind if you haven't completed 5 and 5A. People who don't use my notes before 1/8 and then act like stuff is hard on that day should at least know how they got into that state. (The topics of Notes Part 6 (angular momentum) haven't been stated in class yet, but that's no reason to not work ahead.)

 

The book Chapters are 10 and 11. The way I name the units in my curriculum are Unit 11 (Rotational Kinematics) and Unit 12 (Rotational Dynamics)

 

Rotational Kinematics = learning how to relate alpha to omega to theta

Rotational Dymanic = learning to use Newton's Laws to model forces AND NOW Torques and to deal with centers of mass and moments of inertia and to factor such things into familiar conservation laws, only now with allowance for rotational KE. Also, a new conservation law becomes important: conservation of angular momentum.

 

None of the following are required to be used before January 2, but I know some people will appreciate seeing the terrain ahead of time. I will cover the concepts in all of these things in the classes of January 2 and 4. Then we have a weekend. Then we have the 8th. Then 10th is test.

 

The order of the attachments is very important to heed:

Objectives - inventory of required concepts

Rotation Analogs - access this early

Notes 5 and 5A - have to come after the 4 and 4A you already did, but before the rest below.

SP's - a redundant electronic copy of the hard copy I already gave you

Unit 12 Solving Strategies - notes that reference specific SP's

Worksheet 12.1 - Rolling Races - that will also be the last semester experiment

Worksheet 12.2 - Reviews Notes 3, 4, 5, 5A, and reviews the whole semester

Conservation of Angular Momentum = Notes 6 = deep into the unit. Handled in class late January 4

Cranking Out The Compound Pendulum Collision Answer = unit mastery problem

 

Since the last document on the list above references a unit mastery problem to test yourself, don't look at that document's contents until I've introduced the problem in class. The document in this attachment gives away the answer to the problem, so it's to be used when you're ready for it, but you gotta see the problem first. I attached it prematurely, but I did it so that people who wanted to could see the picture of the things we have left to do.

 

 

Big Post on Rotation Here. This first went up on 1/4, Updated Saturday 1/8. Last 1/8 Update: at 10:30 PM, I'm adding the full solution to SP2, a problem I brought up in class. This paper is clean algebra, no discussion. That's it for updates before 1/8. You do SP2 after you do my Notes Part 5. You do my Notes Part 5, and then you test yourself to see if you can fly solo on SP2. Then you look at my SP2 Solution document.

 

MISTAKE CORRECTION: Since mid-December, the file called Unit 12 Solving Strategies has been in your possession. It's a great, informative file. But as of 9 PM on 1/6, I have corrected two mistakes in it: when in error, it referenced "Rotation Notes Part 4". That should have said "Rotation Notes Part 5". It's now corrected. Also, when in error, it referenced "Rotation Notes Part 5" in an effort to give advice on SP's 12 through 16. It should have said "Rotation Notes Part 6" there. That too is now corrected. (What happened was I made my notes a little better and renumbered some this year.) The corrected Unit 12 Solving Strategies is now attached here, as of 9 PM, 1/6.

 

(Cat Problem Document has been here since Thurs. 1/4. I added one more answer to the end of it on Saturday 1/6. Mallet Problem is now written in Word and attached, identical to how it was on the board in class. Mallet Problem came before Cat Problem. If I attach anything else after Cat Problem on 1/6, it won't be discussion-y, mostly algebra-advice-y on doing solution steps on the SP's.)

 

Mallet Problem and Cat Problem attachments make sure you are aware of the main idea of Thursday's Problems from the board. It will have some solving tips, but more importantly tie everything together with the main idea. In blue ink on the side board was something I'm calling The Mallet Problem. Everyone was to have done it, because I pointed it out. Where I wrote in blue in it, "4. Compare the meaning of this to the I.P. Problem", and "5. Compare to Cat Problem", I now want to make sure that those were not just weird cryptic comments. Everything is tied together well if you paid attention and pay attention to the attachments. In class, I did state what the Cat Problem would be. It's now attached.

 

"IP Problem" refers to the animation of the spinning propeller blade whose answer was 8 radians. Why was that so important as an introduction of certain kinematics equations? If you're paying attention to details in BOTH The Cat Problem and The Mallet Problem, you'll find out. If you don't find out why they are connected to the IP Propeller problem, then you speak up in class.

 

The Mallet Problem had 5 items, was up for an hour, everyone was supposed to solve its first two questions. Those who didn't missed something very important, but I know a lot of people did, because I had conversations with people about it. I wrote it there for a big reason. I also clearly wrote its solution steps by the end of the period, saying "you fill in these blanks to complete the algebraic follow-through". The Mallet Problem's actual final answers are now given in the last page of the Cat Problem document attached. If you did neglect The Mallet Problem in class thus far, its full description, with diagram, is now available in Word form and attached as well, so catching up should be simple.

 

It's very important to take The Cat Problem as a quick practice quiz, and then read its key. And then at the end of its key, you'll see how it connects to the Mallet Problem, whose answers will be stated. And then an enormous connection will be made. I specifically designed January 4's class to set up for that connection. And all the seeds got planted as I intended (as long as you did the Mallet Problem). It's up to you to harvest the crops.

 

The 3rd, 4th, and 5th questions of the Mallet Problem were very conceptual, are the most important thing, and their content is handled on the last page of the Cat Problem. Questions about this most important content are highly expected on Monday, January 8.

 

If you're extremely busy in all of your classes and this Cat Problem/Mallet Problem comparison were the only thing you focused on before 1/8, that wouldn't be the worst thing. Better if you have time to use some of my final exam practice stuff as well, but of course we know that the rest of life can eat into our precious physics time, so I'm posting this to help you know the best priorities in my stuff - the good bang for the buck in rotation right now. I hope this posting has helped with that.

ATTENTION:

 

Anything on this site that says "Due January 8", READ IT and take action. I've been doing additions and updates to all such postings throughout the night of January 6. Most of the content in such postings is old news that's been posted for awhile, but my January 6 additions are supposed to be helpful bits of new answers and reminders.

 

One such reminder:

I'm reminding you on Saturday 1/6, you need to have worked through my notes at least through Parts 5 and 5A by now, and ideally you should be finishing all of my notes through Part 6. (If I write them and give them, it always goes without saying that you become aware of their contents as soon as possible.) I've covered in class the ideas that are handled in Notes 5 and 5A. It's always your job to know what things are in the notes so that YOU can be the most intelligent person about when to use them. For example, by being aware of what's in 5 and 5A (torque), since I gave them early, you then know that their topics (torque) came up big in class, and through that, you were signaled that you're behind if you haven't completed 5 and 5A. People who don't use my notes before 1/8 and then act like stuff is hard on that day should at least know how they got into that state. (The topics of Notes Part 6 (angular momentum) haven't been stated in class yet, but that's no reason to not work ahead.)

Full Rubric to the Conservation of Energy and Momentum Test

Ideal answer set for graded 1D collision summary assignment.

Check Your Omega-90 answer that was due on 1/2/18. Use this spreadsheet.

 

Good quality control on my part: I have two ways of calculating the moment of inertia, and they are represented by Columns B and O in this spreadsheet. Column O matches the formulation that I put into the Notes 4A, and I just added it. Column B pre-existed the Notes 4A before I ever wrote those, and I know that Column B is accurately formulated.

 

Since I made a geometric representation error in Notes 4A, I wanted to make sure that this mistake didn't pollute other things in the document. The document culminates in some algebraic expressions, one of which is the moment of inertia formulation that is in Column O of the spreadsheet. By putting Column O in the spreadsheet and looking to see that its results match those of Column B (which I already knew were accurate) I reassure myself that Page 4 of Notes 4A gives a robust and accurate moment of inertia formulation. (You can also check it by the theoretical integral, which I did, but I could make a math mistake there too.) I'm confident that the moment of inertia part of Notes 4A, Page 4, is unaffected by the geometric representation error that I wrote on the first page. (And I'll next check that the other part of Notes 4A, Page 4, are also unaffected.)

 

For future reference, it's good for you to know the name of the trick that is the basis of the moment of inertia that's in column B. That trick is called The Parallel Axis Theorem. It's part of your required reading, and this is a good chance to see it in action and less abstract.

 

Summary: Column O is more directly from first principles and integration. Column B reveals a nice shortcut that is harder to prove.

 

I hope you make good use of this spreadsheet.

Final Exam Info and Practice. Attachments explain it all. Use the ReadMeFirst one first. Read it and then the FullYearTopicList outline.

 

I might update the FullYearTopicList, but it's good right now.

 

Note the many AP multiple choice practice tests. Fraudulent "Cracking the AP Exam " books are a waste of time when I'm giving you the real deal. Don't have those books in my presence, please. It's like bringing McDonald's food over to the house of someone who worked hard all day to cook you a gourmet dinner. (Brought to you by Carl's Jr.)

 

Postings still to come in the first couple days of break: things like the rubric to the last test, help with the HW due January 2, study guide documents for the rotation unit. There will be a rotation test before the final.

Homework Due January 2 - Calculate your theoretical maximum angular velocity for the swinging experimental beam of December 14. If anyone doesn't comprehend the problem statement, it means the same as what I said in class, so open the attachment and clarify if you disagree.

 

Attached document makes this HW simple. Follow its directions in the order written if you didn't solve the problem on your own. If you did solve the problem on your own, still read this.

 

This is now the final draft version of Rotation Notes 4A. Final update occurred at 10:28 PM on 12/20.

UPDATE, late on 12/15: Almost everyone came and got their test back. Yes! Happy Newton's Birthday, and Happy New Year. I'm here to help those who want to catch up, at all times. You have to diagnose teh necessary adjustment, and a good handful of people who were in the unaware category have begun to do so. In the next day or so, solutions and final exam info are coming online.

 

Somewhere in the big old speech below is this statement: "If this continues, you will end up leaving two-thirds of the final exam unanswered." The "this" refers to letting huge sections of lecture topics (like the work integral) go un-embraced.

 

Last test specifics: People who did not integrate on the last test to go from force to potential energy (on Mechanics 2, Part D). It's impossible to move forward in any physics without that.

 

Anyone who didn't make the work integral second-nature, also didn't prioritize notes that I wrote that were clear on the importance of the work integral; they also didn't prioritize it in class when I performed the integral for gravity. I suspect that they didn't follow it when I didn't, but didn't say anything to ask for clarifying. I don't inherently care about some integral; this is deeper. They've taken something that I stressed repeatedly (in writing and in person), and have act like it doesn't exist. That is what leads to low grades. It's guaranteed.

 

And thinking you reviewed it isn't good enough. If you didn't practice integrating in problem applications, then you didn't do as I instructed, and that was clear in any inabilities with that on the test. I made the skill available repeatedly, and about 25% of the population practiced to make themselves good at it, and that number is stated from test evidence. This isn't an innate skill. It takes practice.

 

If anyone lets things go as if they don't exist and continues this until the end of the semester, their grade will drop by one letter, at least. This isn't a threat. This is an objective statement, because I've done this a long time, and I know how this course of material works. If this continues, you will end up leaving two-thirds of the final exam unanswered. That is why you're reading this right now, because you care to do the alternative which will be awesome.

 

Now I've worked very hard to signal specifically what's expected and to provide practice to do so. And that will continue with great specificity for BOTH rotation work in January and for final exam info.

 

This isn't about being good or bad at things. It's about simply being aware. I just went over the test with an aware person who does read all the things I prioritize. This person thought the test went not-so-great because of some physics errors in some solutions. But the reason this person was greatly rewarded was that all the important language was intact in the things the student wrote. This person saw that the rubric took care of him, and his test turned out quite strong.

 

The bad alternative to this, the meaningless paper, the deal-breaker, is the paper that has in writing  "Energy = Force times distance" for the spring. By writing that, the solver has signaled the following, "hey, Mr. Teacher, all that time you heavily stressed that work does NOT equal force times distance, I didn't register it. I've decided to do different stuff. I'm unaware." And that gets you zero points.

 

These tests are carefully graded with a tight conceptual rubric*, and are in Room 206.

 

All people need to come get them by December 15 for two reasons:

 

8 of 35 people need to come get them now for affirmation of high level language usage that could become permanent with ongoing success in both the near and far future. These aced it, but the grade is the lesser part of the great news here.

 

People not in the population above (and there were people in the population of 28 with B's on the test**) have an opportunity to figure out what they're choosing to miss out on, and as I said in class, coming to get this carefully graded test before leaving school for two weeks off is a big part of that decision to do things differently. That decision is now or never.

 

*People who care should be thankful for the time being put into the tight rubric here. This is a high quality test, and everyone should look for the rubric that I'll soon post. This is part of what I'm talking about when I say not to waste my efforts. And this is why it took 70 hours to correct. I wish it could be under 48, but I don't think 72 is too bad.

 

**A person could earn 9 out of this (26 max) and be gifted a B still, because of the scales that have been pre-set. A person may say "Phew" to this, but that's not the world you want to be living. Why be satisfied with being linguistically weak and acting unaware of central components that I stressed in class? Some people are lucky that this course is generous with test scaling. Scores like 9 are not to be celebrated, B or not, on this particular test.

 

This internet list just went from 9 to 11 subscribers, That's good.

HW due Thursday - Important Details, Read all of this. The end contains references to the final exam and how that's affected by what I wrote in the rest of the message below.

 

HW due Thursday is pivotal for finishing the semester in a way that allows one to do the final exam.

 

This is why it was important to do Tuesday's test with enough time to see the swinging rod (the demo closely connected with the homework). The physical demo was effective, and there are people who didn't observe it Precisely and TWICE: once with the mass at the very end and once with the mass closer to the rotation axis. Everyone was supposed to see the time it took to get through the photogates in both of these scenarios. I was very deliberate and clear in my descriptions of this before the test, and it was for a reason. Those who didn't observe what I just described are now behind and have set themselves up for failure in the entire rotation unit, which the is the most challenging of the semester

 

Being fully invested in the observational part that I just described gives meaning to what I put in the homework document. But regardless, the homework document isn't optional. It'll just have less meaning for those who didn't observe.

 

Once again, observe means: observe twice and record time in both cases, and this was to have been done after guessing with common sense (before measuring) which scenario you think would be faster motion through the photogates.

 

All of the above is why I spent time setting up the photogates. And that's why I spent time carefully describing that goal at the start of Tuesday's class. That was your highest priority in Tuesday's class time, and some people acted like the test that day was the only priority. That was a mistake.

 

Observe this swinging rod with your own eyes as described above, and you'll be set up for success.

 

I shouldn't have to, but the electronic copy of the HW document is attached here. The homework is clearly the document called "Rotational Kinetic Energy Intro and ME Conservation (Pre-Rod)" , as I said in class a couple times ("you have homework; it's the homework worksheet.") The Document says Notes Part 3 at the top of it. Don't worry about the missing Parts 1 and 2 for now.

 

Note: The apparatus in class only had one point mass attached. The document goes through a problem that has two point masses attached. That's fine and it's by design. Go with it, and follow directions. The people who did the specific observation in the classroom will have picked up a concept that will still be relevant even though the worksheet problem has two masses. Again, this discrepancy was as I intended.

 

People who payed attention should find this document fairly easy. But it's the note-set that comes after it that is the most substantial, and then the observation I've been talking about becomes even more substantial.

 

Once the bare minimum HW worksheet due Thursday is done and is seen as very simple review (with one exception), the aware student hopefully says, "I want to work ahead. I want to factor in the mass of the rod itself. I want the 37 pieces of flair." That part is attached here and now. Get to it as soon as you can. It's the document attached called "Rotational KE Budgeting with Rod Mass Notes 4". dot doc

 

Working ahead will help make 2018 a Happy New Year. The third free response problem on the final is heavy duty rotational dynamics.

 

(The second is fluid resistance and the first is something familiar with point particles, by the way.)

Use this link often from now on:

 

 

This is the site that has year after year of Sample Free Response Exams. Go to the site, scroll down to the test from year 2006, select "Scoring Guidelines" for that year, and there you'll see how they did the rubric for the block-slab-friction mock test that I gave you on Wed. 12/6.

 

Note: for people in AP Physics 1, the site will have useful problems for practice even though it is from the AP Physics C exam.

Test Review Stuff: I'll be posting some solutions to various loose end things throughout the weekend.

 

Also, I'm not convinced that all students got the Loose Ends paper that I had available on Friday, 12/8, so it's posted here. But if you go the hard copy in class, you already have it.

 

UPDATED POSTING, as of 6:40 on 12/10: "Working With Any Kind of Potential Energy 2017" is examples of various ways to look at Solutions to Loose Ends Problem 2. It's very thorough.

At 10:49 on 12/10/17: I added the least important answer document: 3 quick easy solutions to questions posed about Hooke's Law at the end of "Working with Any Kind of Potential Energy 2017"

At 9:55 on 12/10/17: I added "Potential Energy That's Unfamiliar" - one more practice at using the work integral. Important for many people.

At 9:00 on 12/10/17: I added Solution Hints to the "Lecture Problem #6" doc.

At 7:46 on 12/10/17: I added Solution Hints to the "Lecture Problem #3" doc. Never changed after

At 6:34 PM: "Working with Any Kind of Potential Energy 2017" was updated. Never changed after

 

That is it for practice problems, solutions, and notes! All that was posted this weekend was just repetition and practice of things that were already heavily stressed in class.

 

The statements below are food for thought:

 

About deriving PE functions that you've never seen before: I did that heavily at the end of class on 12/8/17, Friday. That's supposed to be something you're embracing as a doable task. Again, people who say "I don't get elastic Potential energy" are people who don't understand ANY potential energy. If that is you, then practice using the work integral in ALL cases, including those where you thing U is simply equal to Mgy. (In other words, use the work integral to prove that U(y) = Mgy when gravity is the only force acting and when g is constant. If you don't know every step of that simple proof, then you never understood any force, and therefore you would have to say, "I don't get elastic PE", "I don't get gravitational PE", "I don't get gravitational PE in deep space", "I don't get electric PE". Don't let that be you. Become the person that is comfortable at using the work integral on all of them, and then understands PE due to ALL forces that are spatially dependent.

 

See Conservation Principles where they are relevant and then answer a question in the simplest way possible instead of doing a page of math.

 

You won't see any of the simple stuff if you don't read concepts. The point of these final postings is to help you study conceptually. The exam will have super-simple tasks that take 30 seconds to answer for probably like 3 points apiece, and the hypothetical people who didn't learn concepts will sit at the desk doing half an hour of math for nothing and no points. Notice I called them hypothetical people. It could be no one.

Notes to one of my favorite problems, #56 from Chapter 6 of the AP Physics 1 book.

 

Sunday, 12/10 update: for those of you who didn't photograph this problem's image in class, here is the scenario description, because this practice problem reviews many good concepts:

 

Picture a valley with a straight frictionless valley floor. On opposite sides of the valley floor are two hillsides with masses on them that get released from rest simultaneously. Each mass starts from a height that is 5 meters above the valley floor but the hills themselves go up infinitely higher than 5 meters. The hill sides are curved and frictionless so that each mass speeds up smoothly before gliding frictionlessly along the straight valley floor on the way to colliding with each other head-on. The mass values are 2 kg and 4 kg. They collide in the middle of the valley floor elastically. Complete silence. You are solving for BOTH velocities post-collision and then for the next highest heights they can reach on the respective hillsides when they move and coast back uphill after the collision. (Also, do they ascend up the same hillside together post-collision or on opposite hillsides from each other?) And for that matter, what will happen when they stop at those new heights on the hillside and then come back down the hills (or hill) for a second time?

 

Does it bother you that NEITHER post-collision velocity has been given. Because I said the word "elastic", this is still solvable. Figure out why and do it. If you fail, those posted notes do it rightly.

Elastic 1D Collision Trick Proven Here

 

(How did I program my Collision Pattern Summary Assignment Spreadsheet? Knowing neither final velocity, my spreadsheet always succeeds in predicting both. This spreadsheet helps show how I did that.)

 

This method is valid for energy-conserving situations only, which are an ideal that never actually exists.

Collision Visualization File - For use in class on 12/4/17

Requires Interactive Physics

Big Announcements:

 

1) Reminder: Collision Pattern Summary Assignment (the big chart packet I handed out on Monday 12/4) is due when you arrive on December 6. There is a calculation example for all 7 items attached to this post. If you make the calculations the bulk of the time you spend, you're doing it wrong. The purpose of the assignment is to force Chapter 9 reading and for that reading to correct any careless errors you might make. This is going to be a fast grading by me, and it's at least 15 points.

 

2) I'd like to postpone the midterm from 12/8 to 12/12. If this is a problem, come see me on 12/5. Keep in mind that 12/12 is Boat Day as well. I'm done covering all Chapter 9 things on 12/6. I'm almost done now. The only thing I haven't done is 2-dimensional collisions.

 

3) You have a big study guide on Chapters 7 and 8 with many problems. You're supposed to be using those to prepare. And now you need to keep watching this space for more problems that combine Chapters 7, 8, and 9 together. I'll be adding some, the best being AP exam problems of yesteryear.

 

4) Attached are a couple of little fan-favorite worksheets about momentum and impulse. They make the topic look kinda easy. Worksheet 10-2 ends with a 2D collision, though, and those are more involved. I'm not grading Worksheets 10.1 and 10-2. They're a way to structure studying, as is the thing due 12/6.

 

5) That's enough till Wed. Keep an eye on this space for more Chapter 9 practice.

Due Monday - These are the notes I mentioned that finish the Loop-Cube-Bullet problem. I give you some things to fill in and a final algebraic task to do on the last page of this.

 

Also, read Chapter 9, read the Study Guide that I posted a while ago, and start getting prepared for the next test that covers Chapter 7, 8, and 9.

 

Note: the attachment to this had a mistake when I first posted it. If you downloaded it before 9:40 PM on November 30, you have the version with the mistake in it. But what's here now is correct.

A Formal Proof of The Work Done By Gravity When Far From a Planet's Surface

 

A student asked me to write down every step of the work integral used when expressing the work due to gravity when far from the surface of a spherical attractor. These are situations when F = GMm/r^2 is necessary, and you have to integrate relative to r.

 

The proof is very formal as I handle the dot product as well. I have attached it here. This is not an assignment where you do anything for me. It's a document with math to follow. It's one page, almost all math, with few words. Handwritten, so it's a scanned pdf.

ANSWERS!

 

These answers to the Tuesday 11/28 lecture problems are important, because that day was your central lesson on the topic of Conservation of Energy. Getting good at it now is all about the practice you do. You've been given a lot of problems and a study guide for practice.

 

These three in-class ones were chosen for you to hit central fundamentals, so checking the answers (and other discussion I included) is important.

 

It turns out I did not have a sign error on the third one (something I mentioned in class). I just did my arithmetic too fast and thought I had a negative where I didn't.

 

New Document just added: Examples of how a conceptually-based solution actually looks. What I put in quotes is how it should look from a student. This is in the document that has "Conceptually" in its title. Read the one that has "Answers" in its title first.

HW: The list below is a brief explanation of the postings that are coming here between now and Friday 11/17 at 8 PM, postings that will help you do well with the HW due Monday. As I said in class, the bare minimum that you have to do for HW is "Easy Introduction to Potential Energy" and "Easy, But Not As Easy, First Application of PE." These were both handed out as packets in class, and together, they should add to about an hour. I've posted them here electronically as well. Here's what to expect in the way of postings to come to help you with this HW:

 

1) I'm going to do a little write-up of the Racquetball Popper scenario. It's good to go through the logic of this before doing the two HW packets. It takes about 5 minutes. Conceptually, it's the prequel to the two packets, because its ideas lead to the thought of something called Potential Energy. It's attached; It's the Work-Energy Theorem Comprehension Check.

 

2) Notes on Path-Independent forces. I'll need to post them here. The "Easy, But Not As Easy, First Application of PE" says you need them as a prequel. You do for better depth of theoretical understanding, but the packet is also doable without them. I've just edited them. The "Easy, But Not As Easy, First Application of PE" says "Notes on Path-Independent Forces" is four pages. It's down to three smooth-sailing pages.

 

3) The main meaning of the Inclined Plane HW that was due on 11/16 - Attached is the key to that. This came out kind of long, but it is extremely thorough, and has explanations that I worked hard on that I know some people will like. These explanations are the meaning of the dot product in the definition of work and the terms in the energy budget of the inclined plane problem.

Note: I'm not accepting late hand-ins of the Inclined Plane HW that was due on 11/16. That ship has sailed.

 

4) The two packets "Easy Introduction to Potential Energy" and "Easy, But Not As Easy, First Application of PE" are designed to be very user-friendly and are due 11/20. Everything that's on the Grand Study Guide will enable you to begin working ahead whenever you want.

 

Calendar information is on the Grand Study Guide, so read it. And read the textbook early.

There are two things for HW due Thurs. The one that has no calculus (the inclined plane thing) is self-explanatory, and the reason numbers shouldn't be wrong is that I posted a spreadsheet that was part of the key to the last test.

 

The homework that is "Fluid Resistance to Illustrate the Work Energy Theorem" certainly requires knowledge of integration. If that integration challenge was going to be a problem, people were to have told me by now. The particular integration skill here is often called a "u-sub" integral. Whatever I point out in the attachment here is old news in my class, because the integration part of Quick Calculus was due over a month ago. I never gave a quiz on integration yet. This HW is sort of that, in effect, even though that's not how I intended things. (But some spy told me, "you know, there are gonna be people who struggle with that integral.") Well the spy shouldn't be necessary. There are individuals who have asked me for one-on-on help on u-sub integrals, and I gave it to them, and that's how it's supposed to be. It's the student's job to ask.

 

Attachment: calc help that would contain things people were supposed to have asked me in person by now.

Rubric for the Midterm - final draft. The places to award points are stated in bold font. If I mention another way of getting those points for a particular problem, the point value might be stated again but not in bold font. Knowing the points available is simple by adding all the point statements that are in bold. Of course, for people who read carefully, there will be no ambiguity.

 

If you're in AP Physics 1, there are two problems in the attached rubric that you didn't have on your test. These two totaled 5 points, so your total test points are 5 fewer than what's in bold on the total rubric.

 

The rubric mentions a spreadsheet that can be used to quickly check the final answer on Question 3, and if that final answer is right, you just automatically award the full 5 points, and it doesn't matter how the work is shown. That spreadsheet is now attached to this posting as well. The answer to #3 is different for every student and depends on what values of theta, mu, d, v0, and M were given to the student during the test. I tried to post the spreadsheet so that it already contains all the possible combinations of values that I handed out during the test, but I think a few of the value sets might not be in the spreadsheet yet. If your value set is missing in the spreadsheet, just download the spreadsheet, enable editing, and then type in the mu, d, and v0 I assigned to you, typing it into one of the partially complete rows. ONLY type into columns D, I, and J. For reasons that are too boring to explain, DO NOT type your values into a cell that already has a zero there. Zeroes will automatically change when you properly put your values into columns D, I, and J, and then your ideal test answer will automatically appear in Column M. All people had 2 kg given as the mass, and it cancelled out anyway. Mass wasn't needed in the solution.

Midterm total is 30 points: 29 rubric points available to earn plus 1 point earned if you followed directions regarding paper use and test hand-in.

 

Message to anyone who didn't know the Free-Body Diagram on the circular problem on the midterm, especially those who didn't put the normal force toward the center of the circle: I direct your attention to the SP's, that I've re-attached here. Take a look at SP-2. If this normal-force-toward-the-center thing was going to be a problem, all people were expected to encounter it and ask about it, based on SP-2, at least a week before the test. Such actions clear up misconceptions well before being graded on the midterm. The people who do succeed during the midterm don't do it by magical powers of brilliance. They take the types of practice actions that I just mentioned. And this is why on a few occasions over the past couple of weeks, I stopped the class during Period 4 and said, "Hey, those of you not doing anything, you need to be actively working on the SP's." And on one of those occasions, I said, "Those SP's are your practice test."

 

I did have successful conversations with individuals who were working on those SP's. We talked about specific things like force existence, force direction, relation to acceleration direction, etc. It was on a one-on-one basis, those people got stronger, and it didn't just happen on the last day before the test. And it paid off for them when they did the midterm. Those success stories never get the hype they deserve.

Final Review Material. Keep your eye on this space. I'm gonna keep adding solving notes that I have. Since it's the end of this topic, you should be self-sufficient with few notes needed. These last solving notes I have are just left over from past years. They're not essential. I've already posted a large number of more relevant practice test rubrics over the past two weeks. (But I might as well give you what I have - some solutions to some SP's not asked about, but you already were supposed to have asked about those in person.)

 

First Two Attachments: a list of topics, called Learning Objectives 5 and Learning Objectives 6 - there should be no surprises on the list. Most of the study comes from working on the applications, not so much remembering a list. There are five items in Objectives 6, and the fifth item on the list is Air Resistance. All the details of that topic are not fair to put on the midterm yet, and I won't. (However, you were given a document related to it on 11/7/17, and people have begun working through that document, because the first page of that document DOES make you better at applying Newton's Laws in general, and applying Newton's Laws is what the midterm is all about. It's wise to work on the air resistance document as Unit 6 study before the midterm. Read the next paragraph for elaboration.)

 

For example, what's the first step in an air resistance problem? Drawing the FBD. What's the next step? Deciding which direction is positive. What's the third step? Turning your FBD symbols into an F=Ma-based formula. You can still be expected to know to do those things even if one of the forces is air resistance. However, the specific math of F = kv will not be tested yet, because the F = kv part is something that I just introduced on 11/7/17.

 

USE THE TEXTBOOK FOR PROBLEMS: Any odd problems at the ends of Chapters 5 and 6. You're expected to be doing these to practice APPLICATIONS ON YOUR OWN. The answers are in the back of the book if you pick odd problems. Pick problems I've never mentioned before. (#57 from Chapter 6 is one I have mentioned before, and it's notes is one of the postings here.) Pick challenging ones that seem unfamiliar at first. Pick problems that are blue-numbered; pick problems that are late in the Chapter-set. Pick problems that are early. Do them out of order. 

One Last Study Helper - not urgent. SP-5 with math details written down. Nailed it!

 

This was not a crucial posting - just something I thought I'd do, since some people asked me about setup help on SP-5. We did the set-up fully in class.

 

Hey, this solution invites the thought of other bodies to diagram within SP-5. I mention it in the document, and serious people do these other FBD's. So I'm gonna crank out those additional FBD's and there, I posted that too.

Mock Quiz Solution: Rotating Incline with the Wooden Block Not Sliding While It All Rotates

 

You got the game and the paper problem in class on Wed. 11/1. After you've tried it yourself, here is the solution.

Course Syllabus for AP Physics C

Course Syllabus for AP Physics C

Mock Quiz - Yet Another One. Kid on swing, looked like an alien, was started in class Mon. 10/30.

Become very familiar with what these are like and how they are scored well before the midterm of Thursday November 9.

This should be a strictly timed 20 minute sitting, and then you score how you did with the key.

Mock Test on Applying Newton's Laws - This version contains the diagram and a second problem. The diagram makes it clear that the ratio of the two string lengths from the diagram in class was 2 to 1.

 

This document is being posted for both AP Physics 1 and AP Physics C. The second problem uses some calculus, so it's not expected to be accessible by all students in AP Physics 1.

 

I will soon post the rubric to be used for scoring. You should make the most of this by solving each Mock Test problem with a strict time limit of 20 minutes. Then use my rubric to score how well you did in that time. My rubric will be posted by Saturday morning.

Rubric for the Mock Newton's Laws Test: It's the complete scoring guide to all parts A through F, for a total of 18 points.

 

If you gave yourself only 20 minutes to take the quiz, you score your own, and you call that N. Then you take N, multiply it by the square of 18. Then you take the cubed root of that. That would be your gradebook score out of 18. A 10 raw score, for example, would become 14.8 out of 18, an 82.2%. B+

 

The lowest A in the class is 85%. The lowest B in the class is 70%. The lowest C is 55%.

The Turning Car Problem. This attachment is a set of longer Solution Notes and physics lecturing. You were given a 2-page version of these solution notes in class. The attachment is 7 pages and is thorough about all the related FBD Method steps in such solutions.

Working Ahead: A now-familiar FBD Practice Problem is here extended so you can see where this material is headed.

Simpsons Problem Notes - Knowing what precisely to fill into each blank on this represents strong awareness of some new definitions in Chapter 4 (AP Physics 1) or Chapter 5 (AP Physics C). Being able to do this would represent being caught up on 10/16/17.

HW Packet: The complete FBD's for Tutorial 2 were the bare minimum HW. I'm also asking an in-class understanding question on Monday 10/16 that will be a part of this HW grade. The packet attached here helps you check full grasp of the forces in the problem. The first 4 pages of this attachment were already handed out in class. The remaining pages may help as well. I'm also posting a couple other practice resources for the skill of making Free-Body Diagrams perfect.

A Checklist that can be used to see if an attempted Free-Body Diagram is perfect.

Advanced Free-Body Diagram Practice - Another scenario, another chance for you to diagram it flawlessly. This is about definitions. If you don't read what Newton's Laws (1st, 2nd, and 3rd), this starts to be a waste of time. The textbook (Chapter 4 for AP Physics 1 and Chapter 5 for AP Physics 2) states the three laws clearly. Be aware of what these laws say before doing this problem.

 

Do the entire problem on your own before opening the Key attachment.

Super-Advanced Free Body Diagram Practice: This must NOT be looked at or used until the other practice thing called "Advanced Free-Body Diagram Practice" and its key have been completely digested. This one is the follow-up to that, and would ruin the other one by giving away its answers prematurely.

HW Document for HW due Friday October 6 - Precisely as I assigned it in class, but with notes attached the re-explain the frictionless inclined plane theory. The re-explanation notes are on Pages 2 through 6. The statement of the homework problem is only on the first page.

 

I also added one more problem onto the first page for working ahead. We encourage that here at ConHugeCo.

Due Upon Arrival Thurs 9/28: Knowing that the spring motion scenario had x = A*sin(omega*t) and that velocity was v = (A*omega)*cos(omega*t) and acceleration was a = -(A*omega*omega)*sin(omega*t), predict everything that would be true about the graph of a versus x. (Everything means: that if you think it's a line, then you predict that line's intercept and it's expected slope. As seen in class, the value of A was 3.58 m, and the value of omega was 1.12 s^-1. This is mostly an algebra problem where you are eliminating time t from the final expression as you combine the a(t) expression with the x(t) expression.

 

To do the homework, one only needs to read what's above and act. To check one's answer to the homework, the following information will be useful as well. Attached to this post is an Excel file. You can use it to check your theoretical answer as long as you read its contents correctly. The columns H, I, and J are there to help you make a graph of a versus x, but you have to fill in the rest of Column J. There is already a tab set up along the bottom of the Excel workbook that is called "Answer to HW due 9-28". When you first open the Excel workbook, when you click on that tab, you'll see a blank graph that has been pre-set up. This graph will automatically change and get points filled into it when you do the proper thing in the J Column of the main worksheet that contains the data tables.

Dupas Guest Lecture

A Typical Lab Report Format Example: You may download this file an use it for general structure, just changing the contents to be filled with your specific experiment content.

Homework Due Wed. 9/6 at 8 AM. This problem was described in class and written on the board. It was a two-part problem. It is also rewritten in this set of attached notes that you can access right here. Not only do these notes restate the problem, but they are also designed to help you do it AND to summarize the essential facts that were stressed in class.

 

This note-set has a curious title.