Congratulations! You finished the AP Physics 1 Test.
For those of you who took the test, here is some information about test results, etc.
Dates
May 26: FRQ posted for teachers to see (I think; there’s some confusion on the AP Physics Facebook group about what is actually being released on the 26th).
August 18: Scores released.
The way FRQs are traditionally scored is that the College Board hires teachers for a week session during the summer where the teachers discuss and agree on a scoring rubric, then score all the tests. During the session, teacher scores are routinely audited by lead teachers to ensure that all tests are being scored consistently. This year, the scoring will be done remotely, but will probably utilize Zoom and other sharing platforms to create the scoring rubrics.
Once the FRQ scoring is complete, the College Board looks at the score distribution for both the multiple choice (although there were none of these this year) and the FRQs and normalizes them to produce a consistent curve of 1-5 scores across the years. Their assumption is that each year there should be the same bell curve shape; e.g. if one year more students earn higher scores, then the assumption is that test was easier the year before. This is why it takes until August to get your results…real humans score the FRQs, not machines.
Congratulations to those of you who completed the AP Physics 1 exam.
Project areas
We all have just a few weeks left, and you’ll be occupying your ‘physics time’ working on a project to look at how physics is involved in activities you enjoy. Some examples:
Music: How about sound: Resonance, harmonics, instruments.
Theater: Lighting, sound design and acoustics.
Arts: How do colors mix? How does one carve a statue without breaking stone?
Sports, participation: Energy use, torque, forces, trajectory motion (now you can include air resistance!) Think about things that will help your achievements.
Sports, watching: OK, for the couch potatoes out there, think about sports you like and look at the physics involved.
No examining video games, unless you actually build them and can explain how you use physics in the coding 😁
Environment: Look at the physics of car efficiencies, climate change, alternative energies.
Astronomy: Plenty here.
Modern physics: Relativity and quantum mechanics.
Project format
You can pick about any format you want, but be sure it is a format you enjoy doing.
Slide show (PowerPoint, Google Slides, Prezi, etc.)
Video
Conduct and document an experiment
Musical recordings with written explanations
Research paper
Groups?
You can work by yourself or with one other person. If there is a reason why you need more than two people, check with me before you start.
Completion
Due date
Projects are due by 7:00 AM Wednesday June 3rd. (I was going to say midnight the 2nd, but if you want to stay up all night, I know I won’t be grading them before 7:00 on Wednesday).
Proposal due date
Submit a proposal by Noon on Wednesday, May 20th. I will do a quick check on your proposal that day, to ensure you aren’t either taking on too big a task, or too small of one.
Grading
Remember, we’re on pass/no pass grading now. Please find something that you are authentically interested in, so it’s not just a make-work project, and you aren’t tempted to plagiarize and/or not put any real effort into it.
If you demonstrate authentic engagement, you’ll earn a passing grade on the project.
Thursday 9:00-10:00 AM (this is the morning of the test, so I advice you try not to need to come in at this time.
Please come to office hours with specific questions, or specific FRQs you want help with. I’m really here to help you with questions you have from work you have already gone over, not to provide review lectures. Try the problem, and have the paper you started on available so you can share with me and others what you did. Be ready to use your phone/web cam.
Office hours open to all students
Mon-Fri 11:00 am – 1:00 PM. I’m usually not too busy during these times, but I may also have students from Physics in the Universe who will also have questions about their work.
Please practice these problems by watching the question, trying it yourself, then watching how it is solved on the video. Remember:
Carefully read the question all the way through before you start answering it.
If the problem asks you for a sketch of any kind, include one!
Sketch carefully; use arrows to point out anything you think may not be clear (use the arrows so the words don’t clutter up your sketch).
Remember that Free Body Diagrams (aka force diagrams) only include actual forces, not components.
If you want to add components or anything else to your Free Body Diagram later in the problem, quickly re-sketch it and feel free to mark the new one up any way you need.
Don’t use too many words, but also try to answer using complete sentences.
Correct English grammar and punctuation was designed to make wording clearly understandable. Your reader needs to easily and quickly understand what you are trying to get across.
If a question asks for an equation, write it neatly, with subscripts/superscripts clear.
You don’t want your reader to have to decipher if you mean F=m•a or F=ma.
Remember that you can earn points for what appears to be relatively small details, for example of of the practice tests asks for a force diagram, and the solution was only a dot with one horizontal arrow (correctly labeled, of course).
Don’t skimp on the details; you will more likely gain more points by moving carefully through only part of a question than trying to rush through and leave out important details.
You have learned a lot of physics, but there may be some problems that you just say “I don’t get it…” If you run across such a problem, re-read it carefully, and check to see if there are any bits of information you can provide them to help you collect points.
You should not copy responses from notes or resources. We designed this year’s AP Exams knowing you have access to your notes and resources, so the exam questions will ask you to apply concepts from your notes and resources in new ways. Copying what you have done in the past won’t produce a satisfactory answer.
The College Board suggests you check in 30 minutes before your test time. This will ensure that you have the entire time for your exam.
Format of test
Be sure to watch the following video; it provides much information about test day, and your ability to log in and practice the format two days before.
Methods of submitting, as shown in the above video:
Attach a text file (that you typed in another application)
Copy and paste your response (that you typed in another application)
Attach photos of your handwritten response.
I strongly suggest that you use the last method. Most answers will require some symbols and/or equations, and trying to write them in an online document is usually very time-consuming.
If you are going to write on paper, you need to use white paper and a #2 pencil or pen with black or blue ink, and have your APID and initials written on the top of each sheet. Plan ahead and have ten sheets (or more) of white paper with your APID number and initials on the top. Don’t number the pages in advance, and don’t add your name (they don’t want to introduce potential bias in grading by readers, so your reader will not be able to guess your gender and/or race/ethnicity.
My thought/suggestion: Many of you are most comfortable using your phone. If you are going to be writing on paper, you can taking photos and submitting them from your phone is probably easier than on a laptop/computer.
The day on this poll says Thursday, but just pay attention to the times. I’ll be on Mon-Fri on the most popular time.
I will be providing a Zoom hour for only AP Physics students. If you have not complete a Doodle poll before, you can check off all the times that work for you (there is one evening time). If a time works, but you would prefer not to use that time, you can select “If need be” to let me that you could make that time if that works best for the class.
I’ll set up the AP Physics review as the time that works for most students.
I am still available from 11:00-1:00 Mon-Fri on Zoom.
If you would like to enroll in TheExpertTA to complete the practice problems there (which I recommend highly), follow this link: https://bit.ly/TheExpertTA-VHS TheExpertTA provides problems with hints and solutions.
TheExpertTA is supposed to be free for this semester; please let me know if it ask for you to pay.
I will also continue to post “Flipping Physics” videos that provide both lecture presentations and problems with solutions. Each problem I will write out, then you can try it out yourself, then follow the video and see if you got it correct.
Remember that in our Pass/No Pass grading system, it’s more about keeping yourself present and trying than worrying about what grade you will get. Given all of your grades for the third quarter, none of you should be worried about not passing unless you completely disappear.
Manage your personal College Board account, verify personal email address, locate AP Exam e-ticket, identify colleges to receive AP Exam scores by 6/20/20.
Tech check – ensure your testing device will access the real exam & practice submit your responses. Available 5/4/20 -> use generic password – PRACTICE
Simple Harmonic Motion Introduction(SHM) via a Horizontal Mass-Spring System
Discussion
Simple Harmonic Motion (hereafter referred to by its initials SHM) is a motion where an object moves back and forth due to some external force. Hopefully you can recognize that an object that moves back and forth is changing direction, there therefore is undergoing acceleration, and therefore a force must be applied to it.
The equilibrium position is defined as the position where the net force on the object is zero.
In the first two videos on this page, we are ignoring friction and any other force that would dissipate energy (yes, that magic physics world), and focusing on the force provided by the spring. Hooke’s Law, F=-kx, tells us that the further away from the equilibrium position, the greater the force, and thus the greater the acceleration. When the spring is neither stretched nor compressed, x = 0, and therefore the net force is zero.
Recognize that at the extreme positions—where the spring is compressed or stretched to its maximum—the force is at a maximum, so the acceleration is at a maximum. The block has come to a stop, so its velocity is zero, but its acceleration is greater than zero.
The maximum displacement from the equilibrium position is referred to as the magnitude.
Recognize that the acceleration of the block is not constant, so you cannot use your battery of constant acceleration kinematics equations.
Horizontal vs. Vertical Mass-Spring System
Discussion
In this video, we discover that the video was actually shot in a vertical direction, so there was no friction (only minimal air resistance), and that the video was looped to only show one cycle. Can you explain why he needed to loop the video to keep the amplitude constant? Highlight the text in section below to see the answer.
If you think in terms of energy, and reflect on the bouncing ball lab, you should remember that whenever an object is bent/stretched, available energy is lost as thermal. In the case of the block moving up and down, this energy would slowly decrease the amplitude of the block’s motion, just as the height of the bouncing ball decreased with each bounce.
When is a Pendulum in Simple Harmonic Motion?
Discussion
The question that was raised is ‘what is the restorative force?’ for the pendulum. The students provide good explanations of how it is neither the gravitational force (this remains constant, and therefore the acceleration doesn’t reach zero at the equilibrium point) nor the tension (this is maximum when the ball is at the equilibrium point, which is opposite what we expect for SHM).
It turns out the restorative force can be approximated as the tangential component of the gravitational force—but this only works at ‘small angles’ of less than 15°.
Demonstrating What Changes the Period of Simple Harmonic Motion
The video comes after the discussion; we need to build a conceptual understanding before jumping to the equations.
Discussion
If we compare an object in SHM to a wave, we can see that a cycle in both require a complete movement through all points.
Period: Remember that the period is the time it takes for one complete cycle (e.g. a class period iswas 53 minutes long).
If you think about a sound wave, the magnitude of the wave does not affect the period. A loud C# note has the same frequency and period as a quiet C# note. The same is true for SHM. In SHM, if the amplitude is greater, so is the restorative force and the maximum velocity, so they balance out with the same period.
Conceptually, for a box on a spring, the greater the mass, the less the acceleration will be, so the greater the period. The greater the spring constant, the higher the acceleration, the shorter the period. The full equation is
Conceptually, for a pendulum, the longer the string, the further the ball needs to move, but since the forces do not change, the period is longer. The force of gravity provides the restorative force, so the greater the gravitational force, the shorter the period. The letter g represents the strength of gravity (in N/kg). The full equation for a pendulum is:
Frequency vs. Period in Simple Harmonic Motion
Discussion
This video is just a refresher that frequency and period are in the inverse of each other.
Period is the number of seconds to complete one cycle.
Frequency is the number of cycles completed in one second.
Practice problems
Triple the Mass in a Mass-Spring System. How does Period Change?
If the mass of a block in a spring SHM problem is tripled, what happens to the period? (Try to solve this, then watch the video below.
Flipping Physics is producing videos showing solutions to released FRQs. This page shows a wheel on a ramp problem that includes free-body diagrams and torque/rotational motion.
