Monday, September 26, 2016

Vernier's Ball Toss Lab

I decided this year that if I was going to continue to take the time to teach students how to interpret kinematics graphs of motion (displacement-time, velocity-time and acceleration-time graphs) I was going to bring them up more often during the year. As we transition in my class from basic kinematics equations to projectiles I was looking for a lab that did just that. This is where it pays to keep more resources than you currently use in your curriculum. I found a pdf I had downloaded from Vernier using motion detectors and a ball. The lab looked simple enough and I tried to reproduce the results myself.

The original instructions had called for a wire basket to be placed over the motion detector to protect it from the ball's return. I tried this with a tennis ball and found it very difficult to get the tennis ball to go up and down directly above the sensor. After lots of attempts (seriously like 50)  I was able to get three sets of data to work with:

I wanted students to see what happened at the max height on both the displacement-time and velocity-time graphs and understand what it meant. I wanted them to identify the time that the ball was still being accelerated upwards by their hand (easier on the velocity-time graph by the way). I wanted students to see a constant slope of the velocity-time graph to remember that gravity is constant. I liked how it was coming out but still wanted to make sure that students had an easier time than I did with this lab.

After tweeting to @VernierST I was able to get a few suggestions that made it basically fool proof:
1. Instead of a small tennis ball use a larger basketball (more reflective surface for the sonar).
2. Instead of a wire basket, which I didn't have enough of anyway, try putting two books on either side of the sensor.

Since my books are shorter I had students put two books on either side of the sensor as it was facing up on the table-top (above a picture from their lab). Students got great results and were able to focus more on analyzing the graphs using the tools in LoggerPro. Below is a sample set with the points I asked students to mark in their lab. Overall the lab was actually pretty quick and reliable. I think I could even move up the timing of the lab in my unit as an introduction to gravity rather than a review. Here is the lab I used.

Simple Machine for the win!

Being in California my family takes the drought pretty seriously. We haven't watered our front or back lawn in years. And unfortunately it looks like it. To increase the curb appeal and still keep our water usage low we decide to convert much of our lawn to drought tolerant plants on drip with mulch. As part of the conversion we had to cover 792 square feet with cardboard, overlapping a foot or more at each transition, as a compostable weed block. Even with the start of school I couldn't collect enough cardboard boxes at school to do the job so we ordered a roll of cardboard 6 feet tall and 250 feet long. While it wasn't heavy per se, it was pretty awkward to roll out the 20+ foot lengths I needed.  I had an old diameter wooden closet rod that was over 8 feet long so I shoved that through the middle of the roll and raised it up on two sawhorses.

Since it was above the ground I could easily pull on the end as far as I needed to and the cardboard would roll right off. But then I noticed that the whole roll, well, rolled. In the photo you can see the closet rod was pretty close to the back (right) of the sawhorse. It had started even closer to the front (left). Every few rolls I would have to readjust the rod on the sawhorse and bring it closer to the front. It didn't roll much but every 20 feet or so I would have to adjust it.

That got me thinking. This could be a great example for a Physics class that discusses the Mechanical Advantage of simple machines.  Ask students why the rod rolled, why didn't it roll very much? Usually the "distance in" is the "effort force" which would be the axis in the middle, in this case the closet rod. The "distance out" is the "resistant/ result force" which would be the whole roll acting as a wheel. This may seem backwards for this example since I was moving the wheel and observing the axis roll as a result. Students could calculate the Ideal Mechanical Advantage using the radius of the closet rod (standard 1.25" = 3 cm) and the cardboard "wheel" (2 feet = 30 cm). We would have to assume the machine is 100% to calculate it using distances and not forces.
You could expand the problem for students asking them about the circumference of the closet rod (axis) and how many turns before the rod might fall off the saw horse (assume its 18" wide).

Tuesday, September 13, 2016

Space Time Cord-inates

This is an example of a little idea that grew, changed and evolved and I'm still not done with it.

A colleague asked for some ideas about free fall and I remembered an activity often called Tin Pan Alley; here is a video demonstrating it. Usually done as a demonstration, hex nuts are tied to a piece of string and dropped from a tall height on to a pie pan or other metallic plate. The sound is better on a thicker reusable pie pan  than the thinner single-use ones. First students are shown a string with the hex nuts equidistant, say 20 or 30 cm. When the string is dropped the sound of each hex nut hitting the pan gets closer to the next hex nut than the last. A second string has hex nuts that are at specific (increasing) distances so that when it is dropped the sounds are equal times apart.

After suggesting this activity to my colleague I began to think about it more and decided to use it in my own kinematics unit. In what felt like a stroke of brilliance I thought of turning this teacher-led demo into a student run inquiry activity. I wanted to hand students ten hex nuts, a pie pan and some string and ask them to determine the distance of hex nuts that would create even interval sounds through experimentation. In the first draft I dashed off I actually titled it "Free Falling Nuts." After remembering I teach in a high school I realized it needed a new title.

But there was a sticking point, how can students be sure that the sounds are in fact even intervals? I decided to try and implement some technology.

I had downloaded the free Physics Toolbox app a few months ago and started to play with its many functions. Its an awesome app I strongly recommend downloading. There is a sound meter on there that records decibel levels over a time axis. I wanted students to use this free app to capture their hex nut hits so that they could compare the intervals between them. I also had Vernier Microphones and wanted to try using them as well. I wrote the whole thing up but before I decided to do it I thought I should try it. Turned out to be a good thing.

My colleague Matt and I decided to try it out before we gave the task to our students. We calculated the distances required for even time intervals with 0.1 s or 0.2 s, etc. and made a few prepared strings. We found that the sounds were so short that neither the Physics Toolbox sound meter nor the Vernier Microphones could pick up the sounds well enough to determine the time intervals. We tried amplifying the sound on a large stool, tried recording and slowing down the recording, etc. Without a 1:1 classroom we didn't want to rely on video analysis. We were forced to abandon the idea of students determine the distances by sound. And given that we wanted to use this as an introduction activity we didn't want students to calculate the distances between the hex nuts yet.

So I was back to the idea of a teacher-led demo. I decided to ask students to predict, discuss and then explain what they were hearing. I wrote this google slide presentation to guide the activity. The background data for calculating the distances for different time intervals is here, first calculated out by Matt. The larger the equal time interval, the longer the string. I was limited to a few meters given my ceiling height, something to keep in mind.

Thursday, September 08, 2016

New goals & gravity oops

My regular Physics class starts the year with basic graphing skills and learning how to interpret graphs of motion. Tuesday we used Vernier Picket Fences and Photogates to determine the acceleration due to gravity.

Usually the next day I have students create another planet or moon in our Solar System to create the same graphs based on their acceleration due to gravity (activity here). Starting with the acceleration-time graph (constant horizontal line) students find the area under the curve to plot the velocity-time graph (line with a positive slope) and the area under that curve to plot the displacement-time graph (a power curve).

By this time in the unit my students understand the relationship between the three graphs for something moving with a constant acceleration. They've even graphed something similar by hand; and they saw the same shape with their lab (above). So I found myself wondering, "Why am I making them do it again?" I gave a small quiz last week and noticed that students were having trouble with tangent lines to approximate the slope of a curved line.

So I re-evaluated what I wanted students to learn/ practice with this activity:
- Students need to practice drawing accurate tangent lines and determining their slopes.
- Students should understand that while a constant acceleration creates a positive linear velocity-time graph and a power curve on the displacement-time graph the acceleration will not always have the same value.
- Students often find the area under the curve to find velocity from acceleration-time graphs but need practice finding the slope of a displacement-time graph to determine the velocity and eventually acceleration.

After reflecting on this I changed the activity. I took the acceleration due to gravity at the different locations in our Solar System and worked the data backwards to create the displacement-time graphs for each one. (data here) I printed out enough copies for students to work in pairs and laminated them; I also laminated graph paper. Students were given the displacement-time graphs Wednesday and asked to practice their tangent skills to determine the instantaneous slope at several points. They used these values to create a velocity-time graph on the graph paper using dry erase pens. Note: Overhead projector pens work as well and since they are finer tip would probably have worked better.

Students dove into it, determined to get very close values to the actual acceleration due to gravity. I soon found however that many were trying to use power regressions to solve it; I have quite a few students in AP Calculus. Others found the slope at the beginning and end of the curve, connected those two dots and called it a day. Students were calculating accelerations due to gravity for Mars or Mercury at 400+ m/s2! After some help around the room most students were better about using the tangent method, finding five to six points, paying closer attention to scale, and felt pretty good about their calculations. Yet as students came up to check their answers with me they were consistently twice as high as the actual value. Enough students had almost twice the values that I went back to check my data.

I had calculated d = at2 not d(1/2)at2.

As my students would say, *face palm*; I totally blame the toddler-induced lack of sleep. The students were doing it right (good) and they didn't really know the acceleration due to gravity on other planets anyway so they didn't catch my mistake (even better). In the end I decided it would be a good way of introducing the equation next week and discussing why it is so important to include that (1/2).

I've fixed the data (available again here) and the printing pages (pdf or google doc) and plan to do this again next year. I have very sparse grid lines; depending on your students' math level you might want to give them more grid lines. In the end students were able to practice a skill, broaden their understanding of a concept and I didn't have to grade anything. Aside from my miscalculation, it was a win all around.

Sunday, September 04, 2016

Perusall Trial Update

Back in June I wrote a Blog of Phyz post about the social media textbook reading website Perusall. I set up a Perusall class for teachers to try out. I posted a reading assignment, a paper by Joe Redish called Changing Student Ways of Knowing. I invited teachers to create a student account and participate by reading and commenting on this article. I promised to release grades on September 1st. Thirty-two teachers registered for my Perusall class and took a look at what Perusall can do. Seven teachers left a total of 18 comments. The artificial intelligent agent that scores comments on Perusall gave twelve the maximum score of 2, six received a score of 1. There were no zeros! These were pretty good scores compared to what my students averaged.
I was a little disappointed by the amount of participation in the teacher trial of Perusall. Because the default for automatic grading is 15 students, I had to ask their tech support to grade the assignment. The discussion would have been more interesting if we had a group of 20 commenting like I used with my students. Perhaps I didn't pick an interesting enough article. I still believe in the potential of this tool that encourages students to read textbooks by making it more relevant and useful for them. I am about to start using Perusall in this year's classes. I will use it for the full year and collect data about students use and perceptions. Perusall is free if you upload your own readings, I use the OpenStax physics textbook. Look for another update about Perusall next summer and maybe another teacher trial.

Thursday, September 01, 2016

The Resource Area for Teaching is a Life Raft for Teachers with Limited Budgets

The Resource Area for Teaching (RAFT) was mentioned in a recent discussion on the PTSOS email list. I decided to contact RAFT to see if they could support PTSOS in some way. RAFT Site Manager Ofelia Delgadillo soon replied to my email inquiry with several ways RAFT could help PTSOS, our program for new physics teachers. I won't mention specifics here because I don't want to give away any of the surprises for those coming to the 9/17 PTSOS workshop (registration is still open). I do want to describe my experience visiting the San Jose RAFT location and how they can support physics teachers wanting to do more hands-on activities.

I easily found RAFT on Ridder Park Drive because it is a little past the Santa Clara County Office of Education. I went to the membership desk and joined. The $40 membership fee might be an obstacle to some teachers but it is only $25 to renew. If you can gather a group of 10, the new membership price is only $20 each. Many teachers should be able to get their school to pay for a membership. Either way, it will probably pay for itself on your first visit. As I waited for them to complete my registration, I noticed several teachers making use of the teacher "maker space" called the Green Room. It contains a lot of the equipment teachers need but don't always have access to like laminating machines, book binders, and button makers. After getting my membership card, I went back outside to get a shopping cart.

My first goal was to see if they had some whiteboards for modelling activities. I had to resist looking at all the lab kits as a passed through the front aisles, more on those later. I soon found several boxes full of framed 2' x 3' whiteboards donated by Silicon Valley companies. They were only $5 each. You can make your own for less money but some teachers would find that difficult and/or time consuming. The frames made them look more professional and sturdier. Many still had writing from the last time they were used. Who knows, maybe there is a billion dollar idea still on one of them! I picked out a class set of 10 of the lighter ones and navigated my now loaded cart through the back aisles. These contained art and office supplies, books, extra chachkies from corporate events, and numerous random surplus items like old VHS tape containers and biotech vials. A more creative teacher could work wonders with many of these items but I loaded up on sidewalk chalk.

In the very back is an area where volunteers work. They sort through donated items, update inventory, and package and price items. This would be an ideal place for high school students to get some community service hours. I also noticed the volunteers were assembling the lab kits that drew my attention when I entered. I decided it was time to take a look at those.

The lab kits covered many areas of science but many would be perfect for elementary, middle, and high school physics students. Each kit contains everything you need to build a hands-on device including detailed illustrated instructions, NGSS standards, "To Do and Notice" instructions à la Exploratorium, a description of the background science, and links where you can learn more. I saw many variations of old standbys like roll-back cans, hoverpucks, Benham's disks, and simple motors. There were a few intriguing ones that I was unfamiliar with like roller racers and static merry-go rounds. You can purchase single kits or lab packs of 10. The single kits averaged about $1 and the 10 packs $10. I had to restrain myself from buying them all and managed to leave with 6 of the 10-packs covering a variety of physics topics. Here are some pictures I took of the lab kit displays:
Another great resource RAFT offers is professional development. I have not participated in it but a quick look at their website shows they have a useful program worth exploring. They have scheduled workshops and will customize training for your school or district.
After taking a good look at what they have to offer I am sure you are asking, how can I get in on this? There are 2 RAFT locations in the lucky San Francisco Bay Area and one in Denver, Colorado. Sadly, the Sacramento location has closed. That is hard to believe knowing that the top supporters of education in California, the governor and the state legislature, spend a lot of time there. Perhaps the Sacramento RAFT will return in the future. If you are within driving distance of any RAFT location I highly recommend you plan a visit soon. If you are not, you are in luck, you can order many of their items online. I noticed that there were over 100 of the lab kits available plus many more items in their online store. If you are having trouble visualizing this amazing place, here is a video tour:
My only criticism of RAFT would be to maybe get a better membership card machine:

Saturday, August 27, 2016

Olympics in motion pictures

I want to share all of these with my classes during kinematics! The NY Times posted these great Olympic moments in composite pictures. Often simple motion is modeled for students by showing the object in successive photos in the same image. By comparing the distances between the object over time students can get a sense of how quickly it is moving.
When viewing the page you will scroll down but will actually be moved to the right in order to see their full width. Some of the images like the one above seems to be taken in even intervals of time and would therefore be easier to compare. So how can you use them? Let's take a look:

Christian Taylor's gold winning triple jump:
Notice that Taylor's body makes a parabola while he's in mid air for the long jump. What might be surprising is that there is also a clear parabola in his bounds before his big jump. You can trace over the image along his center of mass and show students the parabola shape. You can also point out Taylor's change in position at the end during his jump and discuss his center of mass.

"On match point in their semifinal, the Brazilian team of Barbara Seixas and Agatha Bednarczuk ousted Kerri Walsh-Jennings and April Ross of the United States."
There are great parabolas to be seen in the projectile motion of this volleyball. The volleyballs are closer together at the top of the parabola because it is moving slower and will not travel as far in between each picture. 

Derek Drouin's winning high jump:
This image shows Drouin's change in speed as the distance between each changes. There is a great parabola during his high jump and you can see him change the position of his center of mass. 

Laurie Hernandez on the balance beam:
I would use this to show students that even when it seems like she's floating on air her center of mass is always supported by a base underneath her. In the first few images show her feet underneath her. The fourth shows Hernandez supported briefly by her hands. As she dismounts you can see a parabolic shape if you follow her center of mass through her flip. 

Anytime you can relate what you're studying to the "real world" for your students is a win.

Sunday, August 14, 2016

The APS DPP is Coming!

I will give you a few moments to catch your breath before providing the details. For those of you who are not excited after reading the headline, here is why you should be. The American Physical Society Division of Plasma Physics offers one of the best educational outreach programs of any professional society. They know what professional development is useful to teachers and how to make teachers feel as important as they really are. If you have been lucky enough to attend one of their meetings when it was in your area then you know what I am talking about. This year's meeting will be in San Jose, California. That makes it worth the drive for thousands of science teachers from Sacramento to San Luis Obispo. They offer 3 days of educational outreach at their annual meeting, Science Teach Day for teachers and the Plasma Science Expo for students.
Science Teacher Day will start at 8:00 AM on November 1 at the San Jose Hilton, registration is open now. This event will be popular and registration is limited so do it early. After an introductory breakfast, it is off to Plasma 101 for Session 1. Plasma 101 has two levels, one for middle school teachers and one for high school teachers. The remaining workshop presenters can now build on what was learned in Plasma 101. After Session 1, teachers pick 2 from the 6 workshop choices that are offered in Sessions 2 and 3. These workshops are full of ideas that can be used in the classroom to teach topics like the electromagnetic spectrum, properties of light, Newton's Laws, astrophysics, and plasma physics. They are appropriate for both middle and high school teachers. The workshops are conducted by the same scientists that are participating in the conference. You can read the workshop descriptions on the APS DPP Outreach website. After the workshops a white-tablecloth luncheon is served and the teachers are treated to a keynote talk by one of the scientists. All teachers go home with a goodie bag filled with educational materials. Here is what one teacher had to say after the Salt Lake City Science Teacher's Day:
Following Science Teachers Day is an open house consisting of educational exhibits by many of the institutions that participate in the conference. This Plasma Science Expo is like a hands-on science museum where each exhibit is staffed by working scientists. Teachers are invited to bring their classes to San Jose's McEnery Convention Center on either of these two days, November 3 and 4. It is open to the public for free on November 3 from 6:00 to 8:30 PM. Just like Science Teacher Day, registration is required and limited. There are some funds available to help pay for buses and substitute pay, so register early.
As part of my role as a Faculty Scholar at LLNL, I have attended the APS DPP conference in Denver, Dallas, Chicago, and Salt Lake City to help conduct one of the workshops. I was able to stay for the Plasma Science Expo in Chicago to help staff the LLNL booth. I work with Don Correll, the former head of the Fusion Energy Program at LLNL and Steve Allen, a magnetic fusion scientist at LLNL and General Atomics. In addition to being leaders in their field, they are both committed to helping improve science education through outreach activities like those at the APS DPP meeting. I am excited about working with them again in San Jose after a 5 year hiatus. We will be conducting the Light and the Nature of Matter workshop at the Science Teacher Day. I hope to see you there. If you have questions, see the links in this post or contact Deedee Ortiz-Arias at or (609) 243-2785.

Friday, August 12, 2016

Begging for free stuff

Let's be honest, teachers are beggars. We have to be.

There are a wide variety of different school situations out there with different funding situations. You may have a one to one device classroom and everything you want (and I might kind of hate you ... not really, but kind of). Or you may have to supply everything yourself for your students. No matter your situation, you have probably at some point asked someone for something for your classroom. Even though you are coming from a good place it can be a little uncomfortable to beg for money or supplies. You get better at it with time, and as you learn about more resources. So here are a few resources and suggestions to help you on your way:

  • Back to school time is the season for donations and generous families. The advantage to asking for donations of money or materials this time of year is that literally everybody is doing it. Families are donating to art and the PTA and education funds and buying school supplies etc. This could also be a disadvantage as families feel overwhelmed and financially taxed. 

  • So how can you still get stuff and families still get to eat? (And if you think that is hyperbola think about how many children in California qualify for free and reduced lunch.) One key is to ask for stuff not money. Our department has a common donation request letter that explains why we need the money (duh) and asks for $20. The back of the letter is filled with stuff that we would love to take. Sometimes parents have unique connections to get us these materials for us. Things we ask for: scrap wood, tools, holiday lights, plastic utensils, mini fridges, toilet paper tubes, hand soap, paper, pencils, etc. One year a parent worked for Dow and gave us enough hand soap to last the Chemistry teachers for years. I tell students that if they can't donate money I would love for them to grab an extra ream of paper or if they have a spare toaster to take apart I'm happy. 

  • Getting to know your students and their families can also open doors. Take advantage of unique resources from families. My TAs used to help block out my windows for our light unit by covering the windows with black garbage bags. One TA got half way through the job and said "I have something better for this. I'll finish it tomorrow." He came back the next day with black posterboard that had been laminiated and fit to cut to size for each of my windows. Turns out his dad owned a print shop. It didn't cost the family much but for me it was priceless.

  • Crowd source your needs. If you have not used before I highly recommend it. I have gotten several thousand dollars worth of materials through Donors Choose donors over the years. When you create an account you have a certain number of points and larger projects require more points but most projects are only worth two or three. I have had local businesses and anonymous donors fund my projects as well as people from across the country. I have a link to my Donors Choose page at the bottom of my emails and on my class website. If the project is of particular high need (as in without it we aren't completing a popular project this year) then I may send out an email to my students and their families asking them to help spread the word. Some teachers also share projects via their own social media sources.
    GoFundMe is another crowd source option that does have an education section. GoFundMe is not education specific and can be used for a variety of things.

  • Know what you want. Dean Baird told me as a new teacher to keep a folder with my wishlist. He suggested we rip the pages right out of the catalogs with what we wanted circled and just toss it into a folder. "Sometimes," he said, "there is extra money that just has to be spent that day. Be the one that has their list together so that you're the one to take advantage." Turns out, he was right. My second or third year I had a lot of English Learners in my class and was asked to attend a training day to learn some strategies to help them. While there I talked a lot with one of the leads of the program who asked if there was material he could order that would help his students learn better in my class. Someone was actually asking for that list Dean made me keep! And I had it ready. 

  • Ask, and you shall receive. It seems so obvious but it is true. Asking for whatever you need is at least the first step to getting it. For years I wanted a bowling ball to make a bowling ball pendulum of my very own. I finally decided I wanted one bad enough to ask. I wrote a very formal letter (on letterhead even) explaining the many uses I had for one bowling ball in my classroom, included my contact information and mailed it to a local bowling alley. About a week later I got a call "Hey, you asked for a bowling ball? For a science class?" I eagerly agreed. "Ummm, do you want twelve?" As I explained in my bowling ball post, I took them. Another time I needed a few pieces of scrap glass for a Mohs hardness test so I asked a local hardware store for broken glass they might have laying around. They obliged, after I explained why I needed shards of glass. There is a "Sale" section of Home Depot's lumber department which has wood at a discount. If its not labeled, and you play the teacher card, it might be even cheaper. (not an official policy)

  • Recycle! Reuse! I've already said I'm a hoarder but because I hoard I don't have to repurchase. Some examples: the base wood for my Rube Goldberg project is reused year to year after the machines have been removed; the magnet and magnet wire in my "Make A Speaker" lab are unwound and used again and again; brads and paper clips from my Electric Building Project are ripped from student projects and kept for the next year.  I even make TAs cut out the used pages of notebooks if half or more is still blank and keep them in reserve.

  • Make it yourself. There are a few demos or classroom tools that you can make yourself instead of purchasing. If you have the know how and are inclines to do so DIY it!
There isn't much in the field of teaching that is easy, but much gets easier with practice. So if there are things that you want for your students, try asking for others before spending your own money. Don't worry, I'm sure you'll still spend hundreds of dollars as a teacher over the course of your career so you don't have to feel guilty. ;)

Thursday, August 11, 2016

Protect that (future) swimmer's ears!

I was so happy to see that baby Boomer Phelps, son of Olympian Michael Phelps, wearing hearing protection at the games this week. Since the announcer are drowned out while I'm watching at home I imagine the aquatic center is deafening. I've been looking but can't find decibel levels from this week's competition.