Saturday, October 26, 2019

Slow your roll

If you're not following Frank Noschese (@fnoschese) on Twitter, why even be a physics teacher with a Twitter account?

And if you get useful mileage out of constant velocity buggies (such as these from Arbor Scientific) but wish you had a convenient, reliable way to curb their enthusiasm, Frank tweets this:



Monday, October 07, 2019

Doggies on a waxed floor



Where will you use it: inertia, friction, centripetal force? I don't think students will mind if you use it for all of those.

Can you stretch it into conservation laws? Of course you can! Low stopping force requires longer stopping time. Impulse/momentum: check. That wee force will need to act across a large distance to change the kinetic energy of those goggies! Work-energy: check.

Want to take it a step further? How did those doggos get up to speed to begin with? Hmmm...

And fear not: it all ends well.



Hat tip to Wendy A. (Rio Phyz ’88). Old physics teacher flex? Why, yes!

Thursday, October 03, 2019

Whiplash Model

As I'm starting Forces and Newton's Laws of Motion in my Conceptual Physics class I am bringing out every demo I've got on inertia. I've got viral videos like the Target Shopping Cart Fail, stuffed animals on toy cars to run into walls, etc. As I was going through my list I realized that I didn't have a whiplash demo. I have plenty of images from physics textbooks and medical journals (Wikipedia version below) but I didn't have a physical representation of one to have in my classroom. And you know what happens when I decide I need a physical model ...
Whiplash.png
By BruceBlaus - Own work, CC BY-SA 4.0, Link


Trying to start with what I had I found the biggest stiffest spring in my cabinet, something that I picked up at the hardware store because, why not? I usually can't get this thing to move much when I hang weights from it unless I'm adding over 2 kg so its a very stiff spring. It is similar to this one from Home Depot, about an inch diameter and almost a foot long.

While a heavy human head analog is best, I was in a pinch so I grabbed a used styrofoam head from our Chemistry department. They usually do a demo using the styrofoam heads about safety goggles and they end up half melting them with an acid (I think). A quick Amazon search shows they are fairly inexpensive. I used a piece of 1/2" PVC that hadn't been cut squarely so it had a crooked sharp end to start cutting a circular hole in the bottom of the foam head base. I kept driving the PVC in, occasionally having to empty the styrofoam core that was forming inside by shoving a smaller dowel through it. Once I had a hole through the base of the head into the main part of the head I tried to enlarge the hole using larger diameter PVC and a hacksaw blade.

Once I thought I had the hole big enough I sliced the head at the neck as if I was decapitating it. I inserted one end of the spring as far into the head as I felt it needed to be to be secure. The other end had to be pulled through the base of the neck. Since I wanted the spring to fit snuggly and a spring that can twist is not rigid enough to push through a hole it took some doing. I found pulling the spring through with a pair of pliers while twisting to work the best.

One end of the spring does stick through the base but I don't think it would have enough of a hold on this base if I made it flush. Since my head has a bit of a base beyond the neck you have to hold on to that part rather than just the portion of the spring that sticks out the bottom to get the right effect. But in the end it worked great!

This is my colleague demonstrating it in real time and then in slow motion because of course you have to:






My future plans are to get another similar spring and redo it with a more realistic head like a hair dresser's practice head. I'd like to secure it to a flat base perhaps with casters under it, so that it is easier to roll along my desk to simulate the crash. But still, I now have a real whiplash model I made with what I had in less than half an hour, it will work for this year!

Wednesday, September 25, 2019

The Forces Playlist of Phyz

The Forces Playlist of Phyz
SONGARTISTYEAR
Carry That WeightThe Beatles1969
First PushDeVotcKa2005
Force of Nature (Bonus Track)Lenka2008
Force TenRush1987
Forces ... Darling (Featuring Earl Zinger)Koop2006
FrictionImagine Dragons2014
FrictionMorcheeba1998
FrictionShame2018
FrictionTauk2014
FrictionTelevision1977
The Girl With the Weight of the World in Her HandsIndigo Girls1990
Grace In GravityThe Story1991
GravityAgainst The Current2015
GravityDaughtry2018
GravityJesse Cook2005
GravityJohn Mayer2006
GravityA Perfect Circle2003
GravitySara Bareilles2008
GravityWith Confidence2017
Gravity (feat. JMR)Jai Wolf2016
Gravity (Stripped)Wage War2017
Please Push No MoreGary Numan1980
PullBlind Melon1996
PullMicrowave2019
Pull ShapesThe Pipettes2007
Pulling Mussels (From The Shell)Squeeze1980
PushMatchbox Twenty1996
PushSarah McLachlan2003
Push on for the DawnCorinne Bailey Rae2016
Stop Draggin' My Heart AroundTom Petty & The Heartbreakers1981
Tension Is A Passing NoteSixpence None The Richer2002
WeightlessAdam French2017
WeightlessBlondfire2004
WeightlessBrina Eno and Daniel Lanois1989
WeightlessChris Burkich2016
WeightlessCity And Colour2011
WeightlessThird Eye Blind2016
WeightlessWashed Out2013
Weightless3112011
Weightless (feat. Shungudzo)Hayden James2019

Saturday, September 21, 2019

Where we are with phones in the classroom

Students being distracted by phones at school began registering in the early 2010s. By the late 2010s, the problem was full-blown.

Teachers and administrators were somewhat flat-footed in their response. They didn't understand the depth of the phone addiction epidemic because they hadn't ever suffered from it. That was a mistake.

Amid the generational gap in understanding, teachers were overrun. Many wearied of pleading and admonishing and bribing and punishing students to keep them from using their phones in class. 

As in any profession, teachers populate a spectrum of professionalism. And at one end of the spectrum, some teachers were delighted to discover that they could produce a silent classroom of happy students by letting them "phone out" (zone out on their phones). Teacher effort required: zero. A perfect pacifier. 

There were also the "treat-em-like-adults" optimists who felt that given free anytime access, 14 year-olds in class would exercise  only use their phones if they truly needed to. They were shocked by the ubiquity of that need. 

There were also jerks like me. I never harbored any patience for unauthorized phone use in class. And my authorizations were few and far between. Very few. The "No Phone Zone" policy is displayed and repeatedly announced. But there were always students who were undeterred. 

Those students were accustomed to teachers begging and pleading. They'd often make an attempt at discretion by hiding their phone behind books or a backpack on the desk. They were in complete disbelief when I assigned them Saturday school upon their very first phone infraction. But that tended to keep subsequent infractions in check to some extent.

Two years ago I cleared out part of my room to make space for a backpack cubbies. Thirty-two: one for each seating location in the classroom. And I authored an accompanying limerick:

The phone goes into the pack
The pack goes into the rack
Kindly observe
That the parking's reserved
In an hour you'll get it all back

The backpack rack is reasonably effective. But phone addiction is strong among teenagers. And getting stronger. Some keep their phone in a pocket rather than surrendering it to the pack which will lie feet away from them for the duration of the period. And, as mentioned previously, my zero tolerance casts me as an intolerant jerk who just doesn't "get it". Some colleagues would suggest I'm not meeting the students where they are.

In 2019, we have sporadic tales of schoolwide attempts to minimize phone distraction in class. My own school flirted with Pocket Points. It required no expenditure and was simple to defeat. Other schools are trying magnetically locked phone bags. The logistics seem cumbersome and, again, teenagers know how to defeat these measures. The addiction is strong.



There is no research that I'm aware of that touts the benefits of student phone use in class. Research to the contrary doesn't seem hard to find. For example:


France has banned phones from classrooms. I don't foresee this happening anywhere in the US. Because
1. many parents delight in having immediate access to their children throughout the school day.
2. classroom teachers, many of whom have all but surrendered on the phone issue, strive to find positive uses for the phones they know will be up and running during class.
3. administrators fall behind in assigning phone-violation discipline as it is. That only stands to get worse with an all-out ban

I will continue to be a No Phone Zone jerk in my own classroom, allowing phone-friendly colleagues to appear "chill" in comparison. Some will argue that students won't be able to concentrate, anxious from having been separated from their phones.

I plan to retire in 2023.

Sunday, September 15, 2019

The threat of gun violence at schools

When I began teaching in 1986, all the doors on my school's sprawling 64-acre campus opened via doorknobs. And those doorknobs locked from the outside. All classrooms open to the great outdoors. We had emergency procedures for fires and earthquakes.

Since Columbine, the doors were retrofitted with exterior pull handles and interior crash bars. The doors can be locked from the inside. Emergency procedures of lockdown and shelter-in-place were added.

In recent years, a predictable pattern has emerged. Whenever an unscheduled lockdown or shelter-in-place occurs (and they are rare), the principal will get messages from concerned parents worried that the school had not taken the threat seriously enough. The verdict of disappointment will be shared, and further drills are scheduled.

We were recently placed on lockdown during our half-hour lunch period. I hustled nearby students (none of whom I knew) into my classroom and locked the room down. I was impressed how quickly the bustling outdoor lunch crowd of 1900+ students cleared into classrooms. The lockdown was eventually downgraded to a shelter in place. An administrator checked my classroom to provide an update.

(We later learned that a proximate shooting threat to a nearby school was made on social media. Nothing came of it other than that the recently expelled student from that school who made the threat was taken into custody in another part of town.)

As far as I could tell, the whole episode went to plan. My room of strangers behaved well and emerged unscathed.

But dissatisfaction was phoned in in the aftermath, so staff underwent additional training, and a followup drill was scheduled.

There is an assumption and expectation that schools (including open-air, indefensible campuses) stand ready to protect students from any attack at any time. No such expectation existed in 1986.

In any case, one thing faculty were warned against was any discussion that would do anything to diminish the fear of a potential mass shooting at the school. Stating the real statistics on mass shootings at school was cast as a no-no.

Don't get me wrong. I believe that the unfettered access to military-grade assault weaponry designed specifically to kill humans on the battlefield is a problem. Mass shootings at schools are a problem. But I'm not keen to put a spin on facts and reality. I listened to this just days after our emergency emergency training session.

On the Media: How to Report on Gun Violence in America


I'm fairly confident that every lockdown incident on campus, no matter how well executed by students and staff, will result in complaints of perceived shortcomings sent in by people who were not present during the incident. This will result in further emergency emergency training sessions and drills.

Sunday, September 01, 2019

Mechanical Universe all episode access page

If you want a single page with easy-to-find links to every episode of The Mechanical Universe, we have something in common.

I made such a page and posted it to my phyz.org domain.

College (half-hour) episode links are on the top table, High School Adaptations are listed on the bottom table. I arranged the episodes into groups that make sense to me. I hope they make sense to you, too.

I use the high school version with question sets in my classes. Links to the question sets on my Teachers Pay Teachers site, The Lessons of Phyz, can also be found on the page.

With all episodes of The Mechanical Universe (college and high school) streaming for free, I'm moving these video presentations away from class time to "YouTube homework."

Since I couldn't find anyone selling or streaming the high school adaptations of The Mechanical Universe, I posted them, myself. I wrote about that in a previous post.

Here's the page: The Mechanical Universe of Phyz.

The Motion Playlist of Phyz

The long-awaited Motion Playlist of Phyz is now here. Enjoy!

This playlist is long. You might want to break it up into two smaller playlists for better results. Or you could pare it down. You could also add to it; I'm sure I missed a few gems. Please let me know in the comments.

Click the "playlist" label in the column to the right to see the playlists for Waves, Electricity, Magnetism, and Light.

SONGARTISTYEAR
Built For SpeedStray Cats1982
Don't Stop Me NowQueen1978
Don't Stop NowCrowded House2007
Don't Try To Stop ItRoman Holliday1983
DriveThe Cars1984
DriveR.E.M.1992
Drive My CarThe Beatles1965
Everyday Is A Winding RoadSheryl Crow1996
Fast CarTracy Chapman1988
Get AroundThe Beach Boys1966
GoIndigo Girls1999
Go Your Own WayFleetwood Mac1977
Going Going GoneMaddie Poppe2018
I Feel SpeedLove and Rockets1989
I Feel The Earth MoveCarole King1971
I'm Not MovingPhil Collins1981
Just A Song Before I GoCrosby, Stills, and Nash1977
Keep MovingIvy2005
Life In The Fast LaneThe Eagles1976
Long Distance RunaroundYes1972
Long Train Runnin'The Doobie Brothers1973
MotionKhalid2018
MotionEmotional Oranges2019
MoveMercyMe2010
MoveSaint Motel2016
Move OnKaren Matheson1996
move!NIKI2019
Moves Like JaggerMaroon 52011
Movin' Out (Anthony's Song)Billy Joel1977
Moving In StereoThe Cars1977
Night MovesBob Seger & The Silver Bullet Band1976
On the Road AgianCanned Heat1968
Out On the RoadNorah Jones2012
Real GoneSheryl Crow2006
Road To NowhereTalking Heads1985
Rockin' Down The HighwayThe Doobie Brothers1972
Roll Me AwayBob Seger & The Silver Bullet Band1982
Roll OnThe Little Willies2006
Runnin' Down A DreamTom Petty & The Heartbreakers1989
Running On EmptyJackson Browne1977
Silent RunningMike + The Mechanics1985
Slow DownThe Beatles1964
Slow Pony HomeThe Weepies2005
Slow RideFoghat1975
SomethingThe Beatles1969
Something In The Way She MovesJames Taylor1968
Speed of SoundColdplay2005
Speedball TuckerJim Croce1973
Speeding MotorcycleYo La Tengo1990
The Long And Winding RoadThe Beatles1969
Train In The DistancePaul Simon1983
When The World Is Running Down...The Police1980
Your Move (Single Version)Yes1971

Sunday, August 11, 2019

Syllabus alternatives

In the last few years I've tried to reflect more on why I do certain things and what the students get out of each. Starting my 14th year I now have way more resources than I can fit in a year and can pick and choose what I want. I am making myself justify each activity, and "because we always have," doesn't cut it. At the start of the year one year I thought about my class syllabus and what I expected students to get out of it versus what my students actually did. I saw it as an important resource of information, a contract between us about how the class would be run with each of us holding up our part of it. My students, and arguably the adults in their lives, saw it as a box to check by signing it without reading it. Students would ask me all year questions that could be answered by reading the syllabus, I would find the copies they were supposed to keep all year on the floor in the first few weeks. So my syllabus was not being read, so it was not working as it was. So I changed it, two different ways for two different classes.

First, I changed my Physics syllabus from two pages of text into a visual syllabus (like an infographic). I loved the one page result that I made using Adobe Photoshop, even printed in black and white students found it much easier to digest.
A few friends wanted their own versions (above left) but I had to edit it for them because they didn't have the software.  This year I rebuilt it in powerpoint (above right) for my Conceptual Physics which makes it much easier to share. It's available here as a pdf so you can see how it turns out and a powerpoint file so you can edit it if you want.

For creating your own I have a few suggestions:
- Use pictures to represent what you can like the book cover and the calculator near the top.
- If you can represent it in a graph, do it!
- Be brief! Try highlighting the important words in your syllabus and see what little is left.

This version is still a paper, that requires a signature and should be kept all year. I retained this part of the traditional approach for my Conceptual Physics students because they will have a notebook in which they keep all their class materials and it will be glued in. For regular physics, as they are older, I will probably not do a printed version again.

When I began teaching AP Physics C and had to draft a new syllabus I again focused on what I needed and why. I wanted my students to read my syllabus as their was important information about the outline of the course. I wanted them to have access to the syllabus to read later but they did not have to necessarily keep the paper. So I decided to make a Google form that had paragraphs from my syllabus interspersed with comprehension questions for my students to answer. I made a similar version for parents with fewer questions and aligned more to things that might concern them more (like the A-/B+ border). The full text version of the syllabus is also posted on Google classroom so my students can access it anytime.

This will be my third year using the digital syllabus in AP and I love it. The students complete it sooner (I can even email it to them the weekend before school starts) and it takes care of a lot of questions because they actually ready it. When our school is completely one-to-one I will probably do a digital syllabus for all my classes but will probably use images like the visual syllabus instead of paragraphs in between.

Friday, August 09, 2019

The evolution of color vision in tetrachromats

Many of us have a sense of color-mixing among trichromats. There's this classic image of the primary and secondary colors of light achieved by overlapping monochromatic circles of primary colors.

We overlap the red, green, and blue in a triangle to produce magenta (red + blue), cyan (blue + green), yellow (green + red), and white (red + blue + green). We have three distinct cone receptors in our retinas, sensitive to red, green, and blue. So this all makes good sense.

But birds have four cones and can seen into the ultraviolet. Researchers say this gives them an additional dimension of color vision. Imagine red + ultraviolet. You can't: we don't have a name for that mixture, nor can we visualize it. A color mix square would be called for. Actually, that wouldn't work.

Seems the number of possible color-mixing outcomes is 2^n – 1, where n is the number of primary colors. Three primary colors yields 2^3 – 1 = 7 outcomes (R, G, B, M, C, Y, W). Then four primary colors produces 15 outcomes. But the color mixing square can only accommodate 13. How unfortunate. Downright unlucky!

Here's what I got when I tried to populate the cells of a color mixing square. D-oh! Now I'm getting why an extra dimension of color is called for here.

For many more details and implications, check out the Science Friday segment below.



When I say I'm a big fan of SciFri and appreciate the science communication work that host Ira Flatow does, you might suspect a "but" is sure to follow. Who am I to disappoint?

Listen again to the minute from 13:15 to 14:15. I cringed when I heard this over the air the first time through. Ladies, has this ever happened to you? Maybe it was the result of multitasking on Ira's part, but I'm reticent to make excuses for him here. In any case: awkward. The guests maintained composure, so good for them. Still though... I hope I'm never that guy (but I probably have been).