The Danger of Misapplying Powerful Tools

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When I was a software engineer, I frequently used powerful tools such as C++ and techniques such as object-oriented analysis and design to implement software that performed complex operations in an efficient and effective manner. I also spent a lot of time sharing these with others. However, I learned to provide a caveat: if misapplied, these tools and techniques can result in a much more significant problem than would result when applying less powerful ones. That is, if you are not skilled in the deployment of these tools and techniques, the risk is much larger than the benefit.

Other engineers didn’t always appreciate this caveat. So, I would try to communicate with an analogy. You can build a desk with a saw, hammer, screwdriver, and drill. You can build a desk more efficiently using a table saw, drill press, and nail gun. If you make a mistake with the hammer, you may loose a fingernail. If you make a mistake with the table saw, you may loose a finger. If you are not adept at deploying the tools and techniques, maybe you should stick with the hand tools until you are.

In reality, the risk of misapplying these tools and techniques is more significant than the impact on the immediate project. The broader risk is that others who observe the troubled project associate the failure with the tools and techniques instead of the application of those tools and techniques. People get the impression, and share their impression, that “C++ and object-oriented analysis and design is a load of crap. Did you see what happened to project X?” Rarely do people, especially people not skilled with these tools and techniques, have the impression that the problem is the application of the tools and techniques rather than the tools and techniques themselves. This, in fact, is a much more serious risk that threatens future applications of the tools and techniques in a proficient manner due to their now tarnished reputation.

A series of articles and posts recently reminded me of my experience writing software and this analogy. I feel compelled to start with a disclaimer since this post has the potential to come across as arrogant, which is certainly not my intention. I have not performed any longitudinal studies that support my conclusions. My conclusions are based on few observations and my gut instinct. I tend to trust my gut instinct since it has served me well in the past. So, if you find this post arrogant, before you write me off, see if these ideas resonate with your experience.

**SBAR**

Let’s start with Standards-Based Reporting and Assessment (SBAR) (a.k.a., Standards-Based Grading (SBG)). Last year, my school started [adapting SBAR school-wide](https://pedagoguepadawan.net/23/growingsbarschoolwide/). SBAR is a powerful methodology that requires proficient deployment. It is not easy to adapt and effectively apply SBAR to a classroom in an effective way that resonates with parents, students, teachers, and administrators. Proper deployment requires a fundamental change in the teacher’s and students’ philosophy of learning. While the effect of a failed deployment on the individual classes is unfortunate, the larger problem is that teachers and parents attribute the problems to SBAR and not its application. It takes much less effort to convince a parent confused about SBAR of its value than it does to convince a parent livid about SBAR due to a poor experience in another class. At my school, one early SBAR adopter stopped referencing SBAR or SBG at all in his class to distance his methodology from the problematic applications. Fortunately, my school has pulled back a bit this year. This is the risk of mandating application of a powerful tool by those not proficient in its deployment. This is not [a unique experience](http://t-cubed-teaching.blogspot.com/2011/10/sbg-goes-up-in-smoke.html).

Two years ago, another teacher and I decided to try to apply SBAR to our Honors Physics class. We mitigated the risk by limiting deployment to six sections of a single class taught just by the two of us. We sent letters to parents, talked to parent groups, discussed the system with students during class. Only after gaining a year of experience, did we attempt to adapt SBAR to our General Physics class which contained ten sections and was taught by four different teachers. The risk of trying to deploy SBAR on this scale initially was too great given our proficiency.

**Technology**

Someone recently shared [this New York Times article](http://www.nytimes.com/2011/09/04/technology/technology-in-schools-faces-questions-on-value.html?_r=2&pagewanted=all) that questions the value of technology in the classroom. In general, a given piece of technology on its own isn’t effective or not effective. Whether technology is effective or not depends as much on its application as the technology itself. It depends on the teacher and the students and the class. Personally, I’ll stick with my [$2 interactive whiteboards](http://fnoschese.wordpress.com/2010/08/06/the-2-interactive-whiteboard/). This isn’t because SMART Boards are inherently ineffective. It is because they aren’t effective for me and my students given my classroom and my expertise. I expect there are teachers out there who use SMART Boards quite effectively. They are probably sick of hearing how they are a complete waste of money.

I hope to have a class set of iPads at some point this year. My school isn’t going to buy iPads for every student. Instead, we’ll put iPad in the hands of 25 General Physics students in my classroom and see what we can do together. Start small, reflect, adjust, expand.

**Modeling**

I participated in a [Modeling Instruction Physics](http://modeling.asu.edu/) workshop in the summer of 2008. I didn’t dare to really start modeling in my classroom until last fall. Why? I believed that the potential risk to my students due to a misapplication of the modeling methodology was tremendous. I decided that it was better for my students to learn what they could via more traditional instruction than what I foresaw as a potential disaster if I misapplied the deployment of modeling. Even more importantly, I was concerned that I could put Modeling Instruction at risk of never being adopted if my failed deployment was interpreted as a failure of Modeling Instruction itself. Only after more research, practice of Modeling Instruction techniques, and discussions with others, did I feel comfortable deploying Modeling in my class last fall. In an attempt to shield modeling from my potential deployment failures, this is the first year that I’ve associated the label “Modeling Instruction” to my class.

I used to be surprised at how adamantly some Modelers warned teachers not to do Modeling Instruction unless they had taken a workshop. I now believe they are worried about the same potential risk that I am. Modeling Instruction is a collection of powerful tools and techniques. Done well, by a skilled practitioner, Modeling Instruction can be incredibly effective. Applied ineffectively, Modeling Instruction can be a disaster and tarnish its reputation. I think students are better served by traditional instruction than by Modeling Instruction applied ineffectively. Traditional instruction may result in a lost fingernail. Ineffective modeling instruction may result in a lost finger. There, I said it. Disagree in the comments. Just don’t take that quote out of context.

While not directly related to modeling, I believe [this recent article](http://www.palmbeachpost.com/news/schools/science-teachers-at-loxahatchee-middle-school-strike-back-1916851.html?viewAsSinglePage=true) supports my conclusions. The problem isn’t that hands-on labs are ineffective, it is that ineffective deployment of hands-on labs is ineffective.

**Conclusion**

I don’t want my thoughts that I’ve shared here to paralyze you into inaction. Rather, I hope that I’ve encouraged you to make sure that you have sufficient expertise so you can apply your powerful tools and techniques in an effective manner. Your students will benefit and the reputation of these powerful tools and techniques will benefit as well.

How do you do this?

* Attend professional development opportunities (e.g., [Modeling Instruction Workshops](http://modeling.asu.edu/MW_nation.html)) that increase your skill with these powerful tools and techniques.
* Apply these powerful tools and techniques in a limited manner as you gain experience and expertise.
* Participate on Twitter, start a blog, read a bunch of blogs, participate in online discussions (e.g., [Global Physics Department](http://globalphysicsdept.posterous.com/#!/)), and subscribe to email lists to accelerate your knowledge of these powerful tools and techniques.
* Observe [skilled practitioners](http://quantumprogress.wordpress.com/2011/08/25/my-grading-sales-pitch/) of these tools and techniques, [find a coach](http://quantumprogress.wordpress.com/2011/10/06/taking-my-pln-to-the-next-level—virtual-coaching/) to observe you, welcome feedback from everyone.

N3L Activity Stations

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While the [Newton’s 1st Law activities](https://pedagoguepadawan.net/147/n1lactivitystations/) serve as a fun and short introduction, the Newton’s 3rd Law activities provide a shared experience that spans several classes. The activities that the students explore are selected to highlight the most common preconceptions that students have about Newton’s 3rd Law. I stress how important free-body diagrams are as a tool in their physics toolbox and that, once they are adept at drawing free-body diagrams and once they actually trust their free-body diagrams, they will be able to explain a number of counter-intuitive situations. I introduce these activities by stating that Newton’s 3rd Law is one of the most easily recited laws of physics and yet is least understood. Here are the activities:

Download (PDF, 35KB)

**Sequential Spring Scales**

Sequential Spring Scales

The spring scales are initially hidden under the coffee filters. Only after students make their prediction are the coffee filters removed. Most students do not predict that the spring scales will read 10 N. Some predict 5 N (the spring scales split the weight). Some predict 20 N (10 N each way adds up to 20 N). In addition to drawing the free-body diagrams, this scenario can be explored further by asking students to predict the reading on the scales if one of the weights is removed and the string is tied to a clamp instead.

**Bathroom Scale**

This station provides an important shared experience that we will refer back to when discussing the elevator problems later in the unit. This station also generates a number of excellent questions such as “would the scale work on the moon?” and “how could you measure mass on unknown planet?”

**Twist on Tug-of-War**

tug-of-war

Students were very interested in this station this year since they were in the midst of Homecoming Week and inter-class tug-of-war competitions were being held. It may have been the first time free-body diagrams were used in the planning of the tug-of-war team’s strategy. The dynamics platform in the photo is a cart build from plywood and 2x4s with rollerblade wheels and has little friction. Most students claim that whoever wins the tug-of-war pulls harder on the rope than the person who loses. Only after drawing the free-body-digram and trusting it, do they realize this is not the case.

**Medicine Ball Propulsion**

Medicine Ball Propulsion

This is a fairly straight-forward station. I often wander by and ask the students exploring it why they don’t move backwards when playing catch under normal situations. I also check at this point and see if they are convinced that the force on the ball by them is equal to the force on them by the ball.

**Computerized Force Comparison**

*This is the most important station in that it helps students truly appreciate Newton’s Third Law.* I setup several of these stations to make sure that everyone has an opportunity to watch the graph in real-time as they pull on the force sensors. This is the standard Modeling activity for Newton’s 3rd Law. For students still struggling to accept Newton’s 3rd Law while working through this activity, I challenge them to find a way to pull on the two sensors such that the forces are not equal in magnitude and opposite in direction. This activity also counters the misconception promoted by some textbooks (perhaps unintentionally) that the “reaction” force follows the “action” force. Students can clearly see that both forces occur at the same time. (We refer to paired forces according to Newton’s 3rd Law, not action-reaction forces.)

**WALL-E and the Fire Extinguisher**

Who doesn’t love WALL-E? I repeatedly loop through a clip from the [WALL-E trailer](http://youtu.be/ZisWjdjs-gM?t=2m26s). In addition to the questions on the handout, I ask students what is incorrect about the physics in the scene. This year, I also showed students this clip that [Physics Club](http://physicsclub.nnscience.net/) filmed several weeks ago:

N1L Activity Stations

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I like to introduce Newton’s First Law with a series of activity stations for students to explore followed by a couple of demos. They have fun and it provides shared experiences which we can refer back to later. Here is the activity sheet that guides them:

Download (PDF, 32KB)

Many of these stations and demos have as much to do with impulse as they do with Newton’s First Law. I mention this and we revisit these stations and demos later when studying impulse.

Most of these stations and demos are fairly self explanatory. However, a few can benefit from a photo. Here is the “Nuts about Hoops & Bottles” station:

nuts, hoop, bottle

You quickly grab the hoop with a fast, horizontal motion. This station can become overcrowded because some students obsess over trying to capture the most nuts in the bottle. (I’ve seen students catch over twenty.)

The “Hitting the Stake” station is perhaps the most surprising to students. It is easy to build and looks like this:

hitting the stake

The “Spin the Human” station works best on teachers with little hair. We have one constructed from pool balls. This one is built with golf balls and a coat hanger:

spin the human

It is best to put the “Chopping Blocks” station in the corner. Some students have an incredible amount of aggression to release.

I’m sure everyone has seen the “Clearing the Table” demo. If not, MythBusters has an [extreme version](http://dsc.discovery.com/videos/mythbusters-tablecloth-pull-high-speed-2.html).

A couple of years ago, I captured the “Egg Drop Soup” demo with the high-speed camera. I usually have all four eggs make it.

What is interesting about these activities is the evolution of this lesson. When I started teaching, these were all demos. I put on the show and the students’ engagement was that they laughed. A few years ago, my team transitioned these from demos to activities. More fun, more engaging. Based on a suggestion from my instructional coordinator, I now introduce each station and have the students record their predictions before get up and start visiting stations. This ensures they actually make predictions since many of these stations are too enticing for them to make predictions before playing with them.

Maybe I’ll let students “Clear the Table” next year.

Next-Time Questions

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One of my favorite resources for developing conceptual understanding of physics are Paul Hewitt’s Next-Time Questions. Older ones are [hosted by Arbor Scientific](http://www.arborsci.com/Labs/CP_NTQ.aspx) and every month a new one is published in [The Physics Teacher](http://tpt.aapt.org/).

These questions often appear deceptively simple. However, a student’s first impression is often incorrect. I find that these are a great way to discuss and refine preconceptions. These questions are intended to be presented during one class and not discussed until the next. I always have students who are so excited to share their answer they are practically bouncing in their seats. I have to remind them that these are “next-time” questions and, therefore, we will discuss them the next-time we meet. I encourage them to discuss them with their friends over lunch or after school.

Hewitt implores us to use them as he intends:


Although these are copyrighted, teachers are free to download any or all of them for sharing with their students. But please, DO NOT show the answers to these in the same class period where the question is posed!!! Do not use these as quickie quizzes with short wait times in your lecture. Taking this easy and careless route misses your opportunity for increased student learning to occur. In my experience students have benefited by the discussions, and sometimes arguments, about answers to many of these questions. When they’d ask for early “official” answers, I’d tell them to confer with friends. When friends weren’t helpful, I’d suggest they seek new friends! It is in such discussions that learning takes place.

Here is one that I recently used during the Balanced Force Particle Model unit.

Next-Time Question

The next time my class met, the discussion of this question consumed almost the entire class time. The discussion started with a review that the forces must be balanced since the book is at rest (the special kind of constant velocity where the velocity is zero). We practiced drawing the free-body diagram for the book which was a good review of the force of friction and the normal force. We were just beginning to explore vector components, and this was a great introduction since the force from the woman’s hand is directly both upward and to the right. We then debated if the force of friction should be directed upward or downward. Students had valid arguments for each. Another student asked if there was a force of friction at all. Eventually, we drew three different free-body diagrams for the cases where there is no friction, where there is friction directed upward, and where there is friction directed downward. A fantastic discussion all centered around a single drawing and simple question.

Some time ago, I reviewed every next-time question, downloaded those that aligned with concepts we cover, and copied them into unit folders so I would remember to use them when the time was appropriate. Now, I just review each month’s next-time question in The Physics Teacher and file it appropriately.

Give one a try in class. I think you and your students will love it.

CV Buggy Lab

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Last week, I participated in a great discussion on Twitter about the various ways Modelers perform the Constant-Velocity Buggy Lab in their classrooms. The CV Buggy Lab is the paradigm lab for constant-velocity and, as a result, Modeling classrooms are filled with toy cars in the fall. I’m not sure why, but it seems that the red cars are always configured to go “fast” and the blue cars configured to go “slow”.1

CV buggies

We’ve always done a CV buggy lab, even before I started modeling, but this year we did something different. To provide some context, before we do the CV buggy lab, students have already completed a mini-modeling cycle involving the bouncing ball and explored non-linear relationships with the sliding box of mass and rubber bands. We have also briefly discussed the concept of position in terms of specifying the location of something relative to a commonly defined point. For example, “my chair is 5 floor tiles from the south wall and 10 floor tiles from the west wall.” Another teacher and I were discussing that since students were rocking these labs, our typical buggy lab that involves only one car might not be as engaging or beneficial. She decided to have students start with both cars from the start. I thought this was a great idea and decided that I also wanted each group to analyze a different scenario which would make the post-lab whiteboards discussion more interesting.

As a class, we go through the usual process of making observations, determining what we can measure, and, eventually, coming up with the purpose for the lab:

To graphically and mathematically model the relationship between position and time for two buggies traveling at different speeds.

At this point, I had to constrain the lab more than I usually would by specifying the starting position and direction for each car. I assigned each lab group a scenario (this allowed some degree of differentiation in terms of difficulty):

1. red positive direction, blue negative direction; red at 0 m, blue at 2 m
2. red positive direction, blue negative direction; red at -1 m, blue at 1 m
3. red negative direction, blue positive direction; red at 2 m, blue at 0 m
4. red positive direction, blue positive direction; red at 0 m, blue at 0.5 m
5. red positive direction, blue positive direction; red at -1 m, blue at -0.5 m
6. red negative direction, blue negative direction; red at 2 m, blue at 1.5 m

Their homework was to draw a picture of their scenario and brainstorm on how they would design the experiment.

The next day, groups designed their experiment. I didn’t provide any additional restrictions. I only verified that their pictures matched the scenarios that I had specified. Some groups decided that their independent variable would be time; others, position; others, distance. One group decided to gather data from both cars at the same time! Another group taped a marker to the back of the cars which traced their paths on butcher paper and allowed them to make more accurate measurements of the actual distance traveled.

When groups started graphing their data, I requested that they plot time on the horizontal axis. Some objected and remarked that if time was their dependent variable it should be plotted on the vertical axis. I explained that I wanted all the groups to be able to share their results which would be easier if we used a common set of axes. I reassured them that the graph police would not come and get them for plotting their dependent variable on the horizontal axis. (Anyone know why this is the convention?)

Some expected and unexpected issues emerged as students began to graph their data. As expected, those groups who chose to measure distance instead of position soon realized that their graph wasn’t going to convey everything they wanted. They went back, and using their picture, calculated positions corresponding to each distance. We use LoggerPro for graphing, and those groups who made time their independent variable, simply added a new column for the position of the second buggy. LoggerPro makes it super simple to graph multiple sets of values on the vertical axis (click on the vertical axis label and choose More…). However, those groups that made position their independent variable had more trouble since LoggerPro only allows one column to be plotted on the horizontal axis. These groups required more assistance and, in the end, I discovered that it was best to create two data sets and name the time columns identically for each. LoggerPro would then plot this “common” time column on the horizontal axis and the two position columns on the vertical axis. Not super simple, but doable.

2 data sets in LoggerPro

Each group drew their picture, graph, and equations on a whiteboard. We did a “circle whiteboard” discussion rather than having each group formally present their results. At first, the discussion focused on how the graph described the motion of the buggies. As students became more comfortable with those ideas, the discussion shifted to comparing and contrasting the different whiteboards. This was the best whiteboard discussion for the CV Buggy Lab that I have ever had. At the end of class, I confidently shared that their whiteboards captured everything that we would learn about constant velocity. We just needed more time to digest, appreciate, and refine what they had already created.

I’ll definitely do this again next year, but I hope to find a way to not assign each group a scenario and yet still end up with a variety of initial positions, directions, and relative motion. Perhaps, if I ask each group to design their own scenario, I can subtly encourage small changes to ensure the variety still exists. Plus, students usually create scenarios that I never would consider!

1 There are many ways to make the blue buggy slow. I have used wooden dowels wrapped in aluminum foil and wooden dowels with thumbtacks and wire. Others have shared that they use dead batteries, electrical tape, and aluminum foil. This year, I tried something completely different. I found these wires with magnetic ends while cleaning last spring (I have no idea who sells them). While in previous years, it seems that in every class someone’s blue buggy has an intermittent connection, I had no problems at all this year.

making a slow car

Physics Club and the Row-Bot Challenge

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Three years ago my instructional coordinator encouraged myself and another physics teacher to start an after school club for students to “do cool physics stuff.” That first year, we focused on building small projects related to physics. We built candle-powered steam engines, homopolar motors, LED throwies, vibrobots, and styrofoam plate speakers. Two years ago, we started with the small projects, but then the students were inspired to launch a near-space balloon. Once the students set their minds to lauching their own near-space balloon, the club transitioned from a primarily teacher-led organization to a student-led one.

Last year, we started with a ping pong ball launcher challenge. After this kickoff, students decided to build a large hovercraft in the fall and then take it on tour to share with the community and excite people, especially younger students, about STEM. In the spring, we [launched our second near-space balloon](https://pedagoguepadawan.net/60/nearspaceballoon/).

While Physics Club has increased in popularity and size in the past three years, we were amazed when over fifty students stayed after school on Friday to join Physics Club. We’re still figuring out how to keep this many students engaged and what our big project will be for the fall. To keep everyone active while we figure this out, we introduced the 2011 Physics Club Row-Bot Challenge:

The club will document this project on [its web site](http://physicsclub.nnscience.net/rowbots). I’ll let you know how it goes.

Why the Row-bot Challenge? Well, we are considering building some sort of remote-controlled craft that can film video hundreds of feet underwater. This challenge may be a good precursor for that.

In addition to kicking off the challenge, the students had a great time filming with the high-speed camera. They are still trimming the footage and preparing the website, but here’s one of my favorites:

We also borrowed a thermal imaging camera that is normally used to diagnose computer hardware issues. While we don’t let the students use this camera, we still found some interesting things to image. One of my favorite was this comparison of an incandescent, CFL, and LED light bulb:

thermal images of light bulbs

While not planned, we also debunked those ghost TV shows. One student noticed that the camera was picking up what appeared to be a thermal ghost inside the adjacent room. This was puzzling until another student realized that the “ghost” was simply my infrared reflection off the glass door in the adjacent room. Science for the win!

The Preconception Eliciting Tennis Ball

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After investigating the motion of a falling object, I ask my students to draw position vs. time, velocity vs. time, and acceleration vs. time graphs of a ball that is thrown upward and then caught at the same height. As I walk around the room, most students have the position vs. time graph correct but struggle with the velocity vs. time and the acceleration vs. time graphs. For those students that struggle, the most common sketch of the velocity vs. time graph is a ‘V’ rather than a straight line with a negative slope. They then struggle to reconcile an acceleration vs. time graph with this V-shaped velocity vs. time graph.

I then model how I reason through these types of conceptual problems. I hold the tennis ball in my hand and ask, “Immediately after I release the ball, in which direction is it moving?” (They confidently say “up.”) I ask, “Immediately after I release the ball, is it moving fast or slow?” (They confidently say “fast.”) I then encourage them to plot that point on their velocity vs. time graph. I then ask while climbing on top of a lab stool, “As the ball travels upwards, how does its velocity change?” (They confidently say “it slows.”) While holding the ball near the ceiling, I ask, “When the ball is at its peak, what is its velocity?” (They confidently say “zero!”)

I now expose their preconception by immediately asking, “What is its acceleration?” (The answers are split between “9.8 m/s/s” and “zero!” depending on the class) I keep the ball near the ceiling and ask one of the students who enthusiastically answered “zero!”, “If its acceleration is zero and its velocity is zero, what would happen to the ball?” After some thought, the student realizes that the ball wouldn’t fall. I then release the ball and it sticks to the ceiling.

This demonstration appears to be sufficiently memorable due to its humor or unexpected outcome, that students can replace their preconception about the acceleration of an object at its peak. After some laughs, a reference to all the balls that are not suspended in midair over the tennis courts, and an [xkcd comic](http://xkcd.com/942/), I continue demonstrating how I reason through the creation of velocity vs. time graphs. I ask the final part, “When the ball is about to be caught, in which direction is it moving?” and “Is it moving fast or slow?” I encourage them to plot this final point and then they have replaced the V-shaped graph with the proper velocity vs. time graph. The slope of their corrected velocity vs. time graph confirms that the acceleration of the ball must remain constant. The tennis ball spends the rest of the class period stuck to the blackboard.

We have a group of Physics teachers that meet at an area school monthly and share ideas. I learned this demo from a great Physics teacher at one of these meetings. He has practiced enough where he can throw the tennis ball and have it stick. He showed us how to modify a tennis ball:

tennis ball demo materials
*Materials: Neodymium magnets, tennis ball, utility knife, hot glue gun.*

magnet glued inside tennis ball
*Slice the tennis ball, squirt in a bunch of hot glue, and stick in the magnet.*

tennis ball sealed
*Seal the slit in the tennis ball and let harden.*

tennis ball experiencing no acceleration
*Stick the tennis ball on the ceiling!*

From Digital Junk Drawer to Online Exploration for Students

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I’m not sure how many people will be interested in this post describing the tools and process I use to transform the bits in my digital junk drawer into online explorations for my students. However, I notice more and more educators using Macs, and, for those who don’t, they may be able to generalize these ideas using their own tools.

I create a topic page in [Schoology](http://schoology.com/) for every unit:

Topic page

This topic page contains a bunch of links at least somewhat related to the unit. Each topic page has categories for simulations, articles, videos, and projects to make. This topic page is from the first unit which is somewhat less focused than the others and, therefore, has subcategories as well. While some of this material will be referenced in class, most of it is just for students to explore and enjoy. When I introduce topic pages, I tell students that when they are procrastinating, they should click on these links rather than randomly browse the web.

Creating these topic pages takes very little effort because of the tools that I use.

Every time I encounter something that may be somewhat related to physics, or at least science, or maybe just education, I drop it in my digital junk drawer which is [Yojimbo](http://www.barebones.com/products/yojimbo/). To be more precise, I tag it as I drop it in Yojimbo. This is as simple as a clicking a button or hitting a keystroke in Safari or NetNewsWire and typing the tags. My tags are organized around the units that I teach, the main concepts that are covered, and the types of activities I perform as an educator. I keep a list of my tags in a text document that I can reference if I can’t remember which ones to use. My Yojimbo window looks like this:

Yojimbo

Yes, I have over 4000 items in Yojimbo and most of them are related to education. Most of the time, I just keep tagging and adding items to Yojimbo. When we’re ready to start a new unit and its time to create or update the topic page, I use Yojimbo’s collections to organize the links that I want to feature:

Collections

It is easy to filter by tags in Yojimbo and sort by date. I review the new items that I’ve added since I last updated the topic page and drag them into these temporary collections corresponding to the topic page categories (the lessons/labs are for items that I want to incorporate into class rather than the topic page). Once I’ve reviewed all of the new items, I highlight all of the items in a category and use [FastScripts](http://www.red-sweater.com/fastscripts/) to run an AppleScript that generates HTML for all the items:


tell application "Yojimbo"
	set urlList to "<ul>
"
	set selectedItems to the selection
	repeat with bookmarkItem in selectedItems
		if the class of bookmarkItem is bookmark item then
			set urlList to urlList & "	<li><a href=\"" & (location of bookmarkItem) & "\">" & (name of bookmarkItem) & "</a></li>
"
		end if
	end repeat
	
	set urlList to urlList & "</ul>"
	set the clipboard to urlList
	
end tell

The script copies the HTML to the clipboard so all I have to do is paste it into the page editor in Schoology.

While I’ve focused on using Yojimbo to make it easy to create these topic pages, this is just one example. When I or another teacher vaguely remembers something, I can usually find it in Yojimbo in a matter of seconds. While I love [1Password](http://agilebits.com/products/1Password), Yojimbo keeps an encrypted record of all my passwords and serial numbers. I also encrypt weekly backups of my web-based grade book since I certainly don’t trust its security. Yojimbo can handle more than just bookmarks, I give it images, PDFs, and text notes referencing journal articles or books which aren’t available online.

And yes, if you are familiar with [Now, Discover Your Strengths](http://www.amazon.com/Discover-Your-Strengths-Marcus-Buckingham/dp/0743201140/) and are wondering, Input is one of mine.

Measurement Uncertainty Activities

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I was inspired after a recent [Global Physics Department Meeting](http://globalphysicsdept.posterous.com/#!/), where we discussed uncertainty, to update the measurement uncertainty activities we do at the start of the year.

Download (PDF, 35KB)

I just finished these activities with my Honors Physics classes.

I have a different purpose in mind for each station beside practicing measuring and the crank-three-times method (I found [this document](http://www.av8n.com/physics/uncertainty.htm) extremely helpful in refining my understanding of uncertainty and introducing me to the crank-three-times method):

1. **area of the desk**: I want students to appreciate that using a reasonable measuring device can result in results with relatively small uncertainties. I also wanted students to appreciate how the uncertainty of individual measurements are compounded during calculations. I was pleased that students mentioned how the curved edge of the desk made this measurement more uncertain and how ensuring that the meter stick was parallel to the side being measured was challenging.

2. **classroom volume**: I want student to appreciate that the uncertainty of a measurement is not solely due to the measurement device (e.g., the meter stick) but also to how you use it (e.g., having to lay meter sticks end-to-end or marking and moving a meter stick). This is also a good opportunity for students to learn to express results using unit prefixes that are easier to comprehend. Cubic meters work better than cubic centimeters.

3. **dime volume**: I want students to appreciate that what is a reasonable measuring device for one measurement is not for another. You shouldn’t use a ruler to measure the thickness of a dime; if you do, your uncertainty as a percentage of your measurement is huge. Students suggested using both alternative measuring devices (e.g., calipers) as well as entirely different techniques (e.g., water displacement of multiple dimes).

4. **time light**: I wrote a LabVIEW VI that lights a bulb on the computer screen for a specific amount of time. This activity reinforces the lesson from #2 (i.e., the uncertainty of measuring a time interval with a stopwatch is overwhelmingly due to human reaction time and not the precision of the stopwatch display). I also wanted to gather this data to calculate the uncertainty of this type of measurement which we can use in future labs. Below are the results.

5. **cart on a ramp**: This also reinforces the lesson from #2 but involves additional uncertainty due to the interaction of multiple people (i.e., one person calling out second intervals and others marking position). Students realized that they couldn’t define a single measurement uncertainty for all position measurements since it appeared that the uncertainty was greater the faster the cart was moving. I also wanted to gather this data to calculate the uncertainty of this type of measurement which we can use in a lab next week.

6. **pendulum period**: I want students to realize that the experimental procedure can have a dramatic affect on uncertainty (i.e., timing 10 cycles results in much less uncertainty than timing just one).

Throughout the day, we captured 275 time measurements for the blinking light. I created a histogram in LoggerPro and calculated the standard deviation:

histogram of time light

The distribution appears to be gaussian in nature and the standard deviation is 0.1 seconds. So, this year, when using a stopwatch to measure a time interval, we will use ± 0.1 seconds as our measurement uncertainty. The actual value programmed was 4.321 s.

Here are the histograms for the position measurements:

histogram of position at 1 s

histogram of position at 2 s

histogram of position at 3 s

The distributions for the position measurements had much greater uncertainty than I hoped. Also, they were more complicated to make; so, I don’t have as much data as I do for the timed light. I’ll have more classes do this activity next week which will provide more data. Regardless, we may need to reconsider next week’s accelerated motion lab since measuring position visually based on a stopwatch time has a very high uncertainty. In past years, we used spark timers and tapes for accelerating objects, but our spark timers no longer make clear dots on the tape. Any suggestions?

Honors Physics Standards

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This year, our entire school is replacing the traditional report card with a standards-based report card. I’m excited that students and parents will see more than a letter that represents their understanding of physics. The standards reflected on this report card, which we call report-card standards, represent an aggregation of several of the more-specific standards and are common across both high schools in our district. For Honor Physics, we have defined the following report-card standards for the whole year:

Report-Card Standards
———————

* science as a process
* understand the basic concepts of kinematics
* understand, explain, discuss, and apply Newton’s Laws
* understand the basic concepts of energy and energy conservation
* understand the basic concepts of momentum and its conservation
* explain, discuss, and calculate the properties of electrostatics
* explain, discuss, and calculate the properties of electric circuits
* understand, explain, and discuss the properties of magnetism
* describe wave type, properties, and interactions
* explain, discuss, and calculate the properties of geometric optics
* understand the relationships among science, technology, and society in historical and contemporary contexts

Below are the more-specific standards that we use for Honors Physics during the fall semester. They reflect a couple of lessons learned during our first two years of standards-based grading. First, we’ve significantly reduced the number of standards. Too many standards made assessment and reassessment too difficult. However, the problem with this is that the standards become too broad for students to know what is expected. So, we supplement each standard with a few daily “learning targets” to make the expectations clear. As documented in the [syllabus](https://pedagoguepadawan.net/117/inspirationalsyllabuschallenge/) for Honors Physics, standards prefixed with (FR), for the more challenging standards that are initially assessed with free-response assessments, count twice as much as the other standards. The first number that prefixes the standard corresponds to the chapter in Giancoli, 5 edition.

I should disclose that, unlike my General Physics class which strongly reflected the Modeling Instruction methodology, my Honors Physics class does not as strongly. That said, many of the pedagogical techniques of Modeling Instruction are incorporated into the class.

Fall Semester Standards
———————–

> SaaP 1 Select reasonable values for uncertainty of measuring devices and calculate uncertainty for derived measurements.
>
> 2.1 Distinguish between and calculate vector and scalar quantities (e.g., distance, displacement, speed, velocity).
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> 2.2 Distinguish between and calculate instantaneous and average quantities for velocity and acceleration.
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> 2.3 Solve problems involving objects with constant acceleration moving in straight lines.
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> 2.4 Analyze straight-line motion by interpreting graphs.
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> 2.5 (FR) solve problems involving falling objects by applying the kinematic equations.
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> SaaP 2 (Lab) Create and populate data tables for an experiment.
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> SaaP 3 (Lab) Measure lengths and time intervals in the laboratory with minimum error.
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> SaaP 4 (Lab) Create graphs from data measured in an experiment.
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> SaaP 5 (Lab) Use graphs of data measured in an experiment to perform analysis.
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> SaaP 6 (Lab) Analyze error in an experiment.
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> SaaP 7 (Lab) Write a complete formal experiment report according to the specified format
>
>
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> 3.1 Add and subtract vectors using graphical and trigonometric techniques.
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> 3.2 Describe the motion of a projectile.
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> 3.3 Solve problems involving projectiles with an initial horizontal velocity.
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> 3.4 Describe the motion of an object, in 1 dimension, in terms of various frames of reference including a boat moving in a current and an airplane moving through wind.
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> 3.5 (FR) Solve problems involving projectiles with an initial velocity at an arbitrary angle.
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> 3.6 (FR) Describe the motion of an object, in 2 dimensions, in terms of various frames of reference including a boat moving in a current and an airplane moving through wind.
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> 3.7 (Lab) Model the path of a projectile based on experimental data and use this model to hit the predicted location.
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> 3.8 (Lab) Compare predicted values based on a model against experimental results.
>
>
>
> 4.1 Explain everyday phenomenon in terms of Newton’s Laws of Motion.
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> 4.2 Distinguish between mass and weight and convert between the two.
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> 4.3 Solve problems in terms of Newton’s second law.
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> 4.4 Solve problems involving friction.
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> 4.5 (FR) Solve force problems using free body diagrams and net force equations for single objects.
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> 4.6 (FR) Solve force problems using free body diagrams and net force equations for objects on inclined planes.
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> 4.7 (FR) Solve force problems using free body diagrams and net force equations for multiple connected objects.
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> SaaP 8 (Lab) Create data tables and graphs to display the relationship between three related variables.
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> SaaP 9 (Lab) Create a general model of the relationship between force, mass, and acceleration based on experimental data.
>
>
>
> 5.1 Know and apply the velocity, acceleration, and forces that comprise uniform circular motion and distinguish from those that do not.
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> 5.2 Solve problems involving objects experiencing a centripetal force.
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> 5.3 Apply Newton’s Law to objects undergoing horizontal uniform circular motion.
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> 5.4 Apply Newton’s Law to objects undergoing vertical circular motion.
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> 5.5 Define Newton’s Universal Law of Gravitation and use it to solve problems.
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> 5.6 (FR) Solve problems using free body diagrams and net force equations for objects undergoing uniform circular motion with forces at arbitrary angles (e.g., inclined surfaces).
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> 5.7 (FR) Solve problems using free body diagrams and net force equations for objects undergoing uniform circular motion in orbit.
>
>
>
> 6.1. Know and apply the definition of work to solve problems involving a constant force and a varying force.
>
> 6.2. Solve problems involving translational kinetic energy and the work-energy principle.
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> 6.3. Solve problems involving gravitational potential energy (GPE) and elastic potential energy (EPE).
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> 6.4. Know the law of conservation of mechanical energy and apply it to solve problems involving translational motion.
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> 6.5. Know the definition of power and apply the equations for power to solve problems.
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> 6.6. (FR) Know the law of conservation of energy and use it to solve problems involving dissipative forces.
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> 6.7. (Lab) Perform an experiment to compare the loss of PE and the gain of KE of an object moving down an incline in order to calculate the force of friction along the incline.
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> 6.8. (Lab) Explain the results of an experiment by discussing the concepts of work, KE, PE and apply the conclusions to other applications.
>
>
>
> 7.1. Use the definition of linear momentum to solve problems.
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> 7.2. Apply the law of conservation of momentum to interactions in a 1-dimensional closed system.
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> 7.3. Apply the law of conservation of momentum to perfectly inelastic interactions in a 1-dimensional closed system.
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> 7.4. Use the definition of impulse to solve problems.
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> 7.5. (FR) Apply the law of conservation of momentum to interactions in a 2-dimensional closed system.
>
> 7.6. (FR) Apply the laws of conservation of momentum and energy to solve problems involving elastic and inelastic interactions in one and two dimensions.
>
> 7.7. (Lab) Use the laws of conservation of momentum and conservation of energy to calculate the initial velocity of a projectile shot into a pendulum.
>
>
>
> 8.1. Know and apply the definitions, symbols, and units for lever arm, moment arm, moment of a force, and torque.
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> 9.1. Know and apply the conditions of equilibrium of concurrent forces to solve problems.
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> 9.2. Know the following terms and their use to solve problems: elongation, stress, strain, shear, elastic modulus, shear modulus, and bulk modulus.
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> 9.3. Know the following terms and use them to solve problems: fracture and ultimate strength of materials.
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> 9.4. (FR) Know and apply the conditions of equilibrium of concurrent forces and parallel forces to solve problems.
>
> 9.5. (Lab) Apply the conditions of equilibrium to find the value of an unknown mass.
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> 9.6. (Lab) Apply the conditions of equilibrium to create a mobile.
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> 9.7. (Lab) Apply the principles of equilibrium, stress, and strain and the characteristics of materials to design a bridge that meets the specifications.
>
> 9.8. (Lab) Apply the principles of equilibrium, stress, and strain and the characteristics of materials to build a bridge that exceeds the required parameters.
>

Spring Semester Standards
———————–

> 11.1. Solve for various properties (energy, displacement, velocity, frequency, period) of a simple harmonic oscillators.
>
> 11.2. Describe the behavior of pulses in strings or slinkies in terms of reflection, superposition, resonance, standing waves, and harmonics.
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> 11.3. Distinguish between transverse and longitudinal waves and define the following in a wave: amplitude, wavelength, frequency, wave velocity, node, antinode.
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> 11.4. (FR) Solve problems involving standing waves in strings.
>
>
>
> 12.1. (Lab) Experimentally determine the speed of sound from the wavelengths and frequencies of several sounds.
>
> 12.2. List the properties of sound and describe how each is related to wave properties.
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> 12.3. Solve problems involving the intensity level of sound.
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> 12.4. Solve problems involving harmonics with string instruments and open or closed-end tube instruments.
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> 12.5. Solve problems involving the interference of sound waves (e.g., beats, shock wave).
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> 12.6. Solve problems involving the relationship between velocity, frequency, and wavelength (including the Doppler Effect).
>
>
>
> 16.1. Apply Electron Theory to the behavior of static charges, conductors, insulators, and electroscopes.
>
> 16.2. (Lab) Apply Electron Theory to describe how an electrophorus can be charged and transfer that charge to other objects.
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> 16.3. Apply Coulomb’s Law to charges aligned in one dimension.
>
> 16.4. Know the properties and calculate the strength of an electric field between two point source electrodes, between two plate electrodes, and inside and outside a spherical shell conductor.
>
> 16.5. (FR) Solve problems involving the electric force and electric field due to charges in two dimensions.
>
> 17.1. Define electrical potential energy, electric potential, and electric potential difference and solve problems involving these quantities.
>
> 17.2. Know the properties of capacitors and solve problems involving parallel-plate capacitors.
>
> 17.3. (FR) Calculate the electric potential due to point charges.
>
>
>
> 18.1. Apply the relationships between current and charge; voltage, current, and resistance; and resistance, temperature, resistivity, and length in DC and AC circuits.
>
> 18.2. Analyze the power dissipated in electrical circuits.
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> 19.1. (Lab) Draw, construct, and analyze a combination circuit given its description.
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> 19.2. Calculate the net resistance in series and parallel circuits.
>
> 19.3. Conceptually evaluate the effect of resistors, capacitors, and meters in series and parallel circuits.
>
> 19.4. (FR) Use Kirchoff’s rules to analyze I, R, and V in combination series and parallel circuits.
>
> 19.5. (FR) Analyze circuits containing capacitors in series and parallel.
>
> 19.6. (FR) Know how meters work and how they affect the circuits they measure.
>
>
>
> 20.1. Explain the cause and characteristics of the magnetic field of a permanent magnet and an electromagnet.
>
> 20.2. Find the direction of the force on a charged particle moving in a magnetic field.
>
> 20.3. Calculate the magnitude of the force on a charged particle moving in a magnetic field.
>
> 20.4. Determine the magnitude and direction of the force on a current-carrying wire in external magnetic fields and magnetic fields generated by other current-carrying wires.
>
> 20.5. (Lab) Build an electric motor.
>
> 20.6. (Lab) Explain why the armature of the electric motor rotates describing what factors affect its speed and direction of rotation.
>
> 20.7. (Lab) Apply the effects of magnetics fields and electric fields on charged particles to analyze the behavior of a cyclotron.
>
>
>
> 21.1. Use Lenz’s Law and the right (or left) hand rule for straight wires and for coils to predict the direction of the induced current and emf when a wire is moved across a magnetic field.
>
> 21.2. Know and use the relationship between magnetic flux and magnetic field strength to solve problems and calculate the emf induced in a wire when it is moved across or within a magnetic field.
>
> 21.3. Describe what is meant by and solve problems involving “back emf” or “counter emf.”
>
> 21.4. (FR) Calculate input voltage, current, and power and output voltage, current, and power for transformers.
>
> 21.5. (FR) Solve problems combining the concepts of circuits, electromagnetic force, and electromagnetic induction.
>
> 22.1. Describe the properties of electromagnetic waves and the major components of the electromagnetic spectrum.
>
>
>
> 23.1. Know and apply the law of reflection and determine image type, image orientation, magnification, f, do, di, hi, and ho given the appropriate information for plane mirrors and spherical mirrors.
>
> 23.2. (FR) Know and apply the three rules for locating images in curved mirrors using ray diagrams.
>
> 23.3. Describe the refraction of light, tell what causes it and what is meant by the index of refraction; describe total internal reflection and the conditions that are required; and use Snell’s Law to solve problems including calculating the critical angle.
>
> 23.4. (Lab) Measure the critical angle for light and calculate the index of refraction of acrylic using the critical angle.
>
> 23.5. Determine image type, image orientation, magnification, f, do, di, hi, and ho given the appropriate information for spherical lenses.
>
> 23.6. (FR) Know the three rules for making ray diagrams for lenses and apply these rules to find the size, location, and type of image formed.
>
> 23.7. (FR) Solve problems involving combinations of lenses.
>
> 23.8. (Lab) Find the focal length of a double convex lens, investigate the kind of images formed at various distances by convex and concave lenses.