Answers to Multiple Choice Practice AP Test given in class on Tues. 1/16/18:

 

1. D

2. A

4. B

5. B

6. C

7. C

8. C

9. A

10. D

12. C

13. C

16. A

17. A

18. B

19. A

21. C

25. B

26. B

27. D

31. B

32. C

33. D

34. D

35. B

36. B

39. A

40. A

41. C

42. D

46. B, D

47. B, C

48. C, D

Solution to the Second Rotational Equilibrium Quiz

 

Again, expecting something to be really hard and wasting the whole period on it, and burning away time that was supposed to be spent on the practice finals, is a terrible choice. And it is a choice. It's a choice that was made when the student decided that NOT ALL definitions don't matter. And that happened over a matter of more than a week. Knowing definitions are what make this a 5-minute quiz solution. If you disagree, it means you didn't learn all definitions. I put then in writing as a checklist.

 

It was a three force problem with a two-torque balance. So that's as simple as these problems can be. But people who refuse to change their prioritization of definitions will never see that. (In this case, it's definition of where the force is drawn, definition of origin, and definition of leverage as it relates to lever-arm. And definition of which torques are out of the page and which are in. And torque equilibrium. This is all old news by now, which is why I'm saying 5-minute solution.)

 

A perfectly done FBD would make all of the following simple and quick to see. But not everyone does that; not everyone has trained themselves to know where forces go, and not everyone has trained themselves to identify leverages by definition. So all the people who don't do those things, they will take infinite time solving this quiz and still have nonsense, because they live in a world of making simple things impossible. Those who don't live in the world of impossibility, because they prioritize the definitions I tell them to, will do the following in just a couple of minutes, because they will have made a simple FBD in about 1 minute.

 

I gave a known mallet force vector located a given number of centimeters from the pivot axis. The values of these quantities were (0.94 kg)g and 6 cm, (0.88 kg)g and 8 cm, (1.69 kg)g and 5 cm, or (1.175 kg)g and 4 cm.

 

I told people to solve for an unknown ruler mass, and I told people that the ruler was 100 cm long.

 

So a person who has followed directions over the last 2 weeks has placed the unknown mg vector at the 50 cm mark on the ruler. Then the two-torque balance expression (using the givens (0.94 kg)g and 6 cm as an example) became:

 

(Torque-CCW) - (Torque-CW) = 0

 

Torque-CCW = Torque-CW

 

"[(0.94 kg)g](6 cm) = (mg)(50 cm)"    to cancel the g and solve for m would be a pretty good solution, but it is wrong.

 

A quality F.B. diagram shows that the leverage that goes with mg is not 50 cm. It is 50 cm times the cosine of 20 degrees. Working out that the leverage would be 50 cm times the cosine of 20 degrees is something that would be done on scratch paper, and it's a component job that I've shown countless times in class by now. (It uses SOHCAHTOA.) If you don't do the manipulation on scratch paper to get components like 50 cm times the cosine of 20 degrees, but I've done it in front of you countless times by now, well, when are you going to start doing it? (And those who don't know that such a component is important, well then you don't know the definition of leverage, and that's what I'm talking about. I've explained it many times. When are you going to change this if you haven't yet?

 

Correct last step:   [(0.94 kg)g](6 cm) = (mg)[(50 cm)cos(55)]        Cancel g, solve for m.

 

Answer: m = 120 g

 

This was a 5 minute quiz.

Higher Caliber AP Exam Mock Test Material:

 

Know this site:

 

lots of Free Response Practice material there. And rubrics.

 

On Tuesday, I'm handing out a mock AP Physics 1 practice multiple choice test that I'm not allowed to post.

 

Attached here are a couple of old AP multiple choice tests and answers. Questions not relevant to the course have been cut out of the original test documents. If you have 1993 or 1998 test documents that don't say the word "Abridged" in their file names, discard what you have and open up these instead. I've reduced these to 4 pages each for you to eliminate busywork for you.

 

 

Answers to even textbook problems that I suggested in Chapter 8:

 

22. T = 392 N, Pole force horizontal = 339.5 N, Pole force vertical = 0

 

24. a) f = 267.5 N, n = 1300 N, b) 0.324

 

20. b) T = 342.6 N, upward friction = 683.3 N, rightward normal = 171.3 N, c) 5.14 m

 

28. 2.8 m

 

In the meantime, here's a checklist to see if your study has included all relevant things. One page and thorough. It mentions a lot more problems than I mentioned before. You can do as much practice as you like or have time for to build strength.

Ideal answer set for graded 1D collision summary assignment.

Chapter 8 Documents: Posted Here Now. Learn ASAP. Pop quiz sometime in the week of 1/8/17 but not on Monday. Rotation Equilibrium Notes Parts 1 and 1.5 are just repeats of what was already taught in class. Rotational Equilibrium Notes Part 2 is a higher level application problem. And look, you now have a document with solution advice that goes with Chapter 8, #26.

 

As I said in class, your job is to challenge yourself with the 4 or 5 Chapter 8 problems that I highlighted. Where those problems involve components of vectors, you're doing strong work. Should be a fun topic to end the semester on.

 

Conservation of Energy and Momentum Test - Original Questions - I said I'd post these. If you screwed up this very simple test, it's imperative that you look at this now to get ready for the final.

 

 

And remember the ruler problem that I did as a demo? The one where the two little masses sitting on the ruler were 3.7 grams and 7.4 grams, and the whole thing balanced on 48.2 cm, and the little masses sat on 0.5 cm and 99.5 cm? Remember that? You were supposed to calculate the mass of the ruler from all of that. That answer was 90.65 grams. I made one mistake. I should have had one of you walk the ruler to the scale and weigh it so that we could yell PHYSICSSS!!! Anyway, if you didn't do that problem in class as I instructed, you have a chance to catch up, because this paragraph is very descriptive. Go through the FBD equilibrium method, with torques, and practice by proving this answer.

 

 

Final Exam Topics - starting paper - with some crude practice problems

 

These sample MC attachments: this is to get you used to CollegeBoardish exam questions in multiple choice. (There will be some multiple choice questions on the final taken from old AP exams.) Take it like a test, doing the questions that have been covered in class and skipping topics we haven't gotten to yet. See how it goes. I posted exams from 1993 and 1998. Do this early. People who only use these multiple choice exams when the final is days away are people who get ZERO benefit from them.

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.

Some Problem Tutoring from specific even problems off of the Chapter 6 Study Guide

 

There is also Help on #50 there. It's in the document labeled as #58.

 

#56 is my favorite.

Study Guide for finishing Chapter 5 and 6 study/practice

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.

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 6 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) 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.

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

Requires Interactive Physics

Notes for Staying Caught Up December 4: I'm not grading anything on December 4, and I'm actually going to provide a hardcopy of this document to everyone on December 4 in class. However, if you're reading this statement on December 3, and you have time, you can and should start using the document now.

 

Since I referred to the topic of these notes before the Earthquake drill last Thursday, it's in people's interest to gain some familiarity with the document before December 4 if they have time. I regret that it took me longer to post than I indicated, and I also wanted to keep it to 2 pages (it's actually 4), but I did do a good job customizing this document precisely to where Period 5 of 2017 was on 11/30. I also did well telling you all that we're into Chapter 6 now. So wise study-aheaders have had enough info for moving on. Whatever you have time for before Period 5 on Monday (whether it's zero or all of it) will be a greater-than-or-equal-to-zero benefit, and you're set up to know what's going on when you come to class on Monday, December 4.

Answers from the On-the-Board Lecture Problems of 11/28/17:

 

Also, the Chapter 5 and 6 test day will be Thursday December 14. Study Guide coming, but finish reading the book ASAP.

Sorry, I almost forgot to post this. I'll be fair.

 

But anyway, this is here to help you check how you're doing the Air Track Tape Friction Experiment.

 

This document's Pages 3 and 4 are just a reminder of the basic way of using kinematics and Newton's 2nd Law to solve for the coefficient of kinetic friction. The idea is to get an answer and then be set up for comparison as follows:

 

Go to Checking Your Air Track Methods, and go through that step-by-step to calculate the friction again. You are looking for the two separately derived friction values to be identical as a check of understanding.

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 25 points: 24 rubric points available to earn plus 1 point earned if you followed directions regarding paper use and test hand-in.

Answer to Textbook Problem, Chapter 4, Number 50:

 

The answers are 18.5 N for F and 25.8 N for n.

 

Take the problem a step further. Figure out the strongest F is allowed to be if the mass is not to slide up the hill. New problem, new solution, do it yourself before you open the attachment that has the answer.

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.

HW is Chapter 4, Problem 68. These are the Problem 68 Notes

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.

HUGE Success: You've gotta open these as soon as possible. HUGE Lesson learned here. Do NOT ignore this. Best thing to happen so far this year in Period 5. Look at these two attached files to see why. Grand Slam

 

On October 10, I indicated to the class that the experimental methods of October 6 were insufficiently disciplined to yield a data set that would make the lab effort the most optimum use of time. So at the beginning of October 10, I made a case for a more disciplined and efficient lab effort, and the students of Period 5 responded and executed a more disciplined and efficient lab effort.

 

Look at the two attached files to see the fruits of your labors. The File whose title says "Initial Effort" is from October 6. The file whose title says "Disciplined Effort" is from October 10. Open them and compare. (October 10's time numbers are exactly as students yelled to me at 12:11 PM on October 10.) As you look at the difference in results between October 6 and October 10, consider how you individually approached it differently to yield the more disciplined set of results that were obtained on October 10. Use this opportunity to internalize the best lab thinking habits that can be learned from this. (This last idea might be different for individual students.)

 

Working ahead (the 37 pieces of flair): Now that you have a line, look at its slope. Your class got 10.27 m/s/s for the slope. We are working toward how Chapter 4 can teach what the theoretical value of that slope should be. In other words, guess why I think 10.27 m/s/s indicates very strong technique. (Note: this line refers to plotting acceleration versus the sine of theta, not plotting acceleration versus theta.)

HW for before October 10. I said to come up with some possible functions of angle that might fit the Raw Graph that you see in this file posted that I also showed clearly in class.

 

Come to class on Tuesday with awareness of some possible functions of angle (at least two) that might be relevant.

Solution Breakdown: Chapter 2 Problem 35

Solution Breakdown: Chapter 2 Problem 41

Solution Breakdown: Chapter 2 Problem 49

Due Right Now: That you be aware of this study guide and start using it for more practice in Chapter 2. Quiz Wed. Oct. 4

Inclined Plane Solving Notes: This is for making sure you are caught up. These are thorough 2-page notes that highlight precisely the point of my math usage in class on 9/20/17, and why I referred to the Page 36 equations. This is important for your goal of being linguistic in your use of math in physics. In other words, designing your own mathematical solutions instead of being at the mercy of formulas.

The Excel file that goes with the Inclined Plane Problem - See the Word posting also connected to this. Important summary notes are there - needed because you like to check your own understanding.

Dupas Guest Lecture Ball Bounce Data Set

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.

Course Syllabus - Students are responsible for knowing course policies that are described in this document.