Monthly Archives: August 2011

From Digital Junk Drawer to Online Exploration for Students

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 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. 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:


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:


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 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 &amp; "&lt;/ul&gt;"
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, 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 and are wondering, Input is one of mine.

Measurement Uncertainty Activities

I was inspired after a recent Global Physics Department Meeting, where we discussed uncertainty, to update the measurement uncertainty activities we do at the start of the year.

Measurement Uncertainty

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 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

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 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).

2.2 Distinguish between and calculate instantaneous and average quantities for velocity and acceleration.

2.3 Solve problems involving objects with constant acceleration moving in straight lines.

2.4 Analyze straight-line motion by interpreting graphs.

2.5 (FR) solve problems involving falling objects by applying the kinematic equations.

SaaP 2 (Lab) Create and populate data tables for an experiment.

SaaP 3 (Lab) Measure lengths and time intervals in the laboratory with minimum error.

SaaP 4 (Lab) Create graphs from data measured in an experiment.

SaaP 5 (Lab) Use graphs of data measured in an experiment to perform analysis.

SaaP 6 (Lab) Analyze error in an experiment.

SaaP 7 (Lab) Write a complete formal experiment report according to the specified format

3.1 Add and subtract vectors using graphical and trigonometric techniques.

3.2 Describe the motion of a projectile.

3.3 Solve problems involving projectiles with an initial horizontal velocity.

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.

3.5 (FR) Solve problems involving projectiles with an initial velocity at an arbitrary angle.

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.

3.7 (Lab) Model the path of a projectile based on experimental data and use this model to hit the predicted location.

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.

4.2 Distinguish between mass and weight and convert between the two.

4.3 Solve problems in terms of Newton’s second law.

4.4 Solve problems involving friction.

4.5 (FR) Solve force problems using free body diagrams and net force equations for single objects.

4.6 (FR) Solve force problems using free body diagrams and net force equations for objects on inclined planes.

4.7 (FR) Solve force problems using free body diagrams and net force equations for multiple connected objects.

SaaP 8 (Lab) Create data tables and graphs to display the relationship between three related variables.

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.

5.2 Solve problems involving objects experiencing a centripetal force.

5.3 Apply Newton’s Law to objects undergoing horizontal uniform circular motion.

5.4 Apply Newton’s Law to objects undergoing vertical circular motion.

5.5 Define Newton’s Universal Law of Gravitation and use it to solve problems.

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).

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.

6.3. Solve problems involving gravitational potential energy (GPE) and elastic potential energy (EPE).

6.4. Know the law of conservation of mechanical energy and apply it to solve problems involving translational motion.

6.5. Know the definition of power and apply the equations for power to solve problems.

6.6. (FR) Know the law of conservation of energy and use it to solve problems involving dissipative forces.

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.

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.

7.2. Apply the law of conservation of momentum to interactions in a 1-dimensional closed system.

7.3. Apply the law of conservation of momentum to perfectly inelastic interactions in a 1-dimensional closed system.

7.4. Use the definition of impulse to solve problems.

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.

9.1. Know and apply the conditions of equilibrium of concurrent forces to solve problems.

9.2. Know the following terms and their use to solve problems: elongation, stress, strain, shear, elastic modulus, shear modulus, and bulk modulus.

9.3. Know the following terms and use them to solve problems: fracture and ultimate strength of materials.

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.

9.6. (Lab) Apply the conditions of equilibrium to create a mobile.

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.

11.3. Distinguish between transverse and longitudinal waves and define the following in a wave: amplitude, wavelength, frequency, wave velocity, node, antinode.

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.

12.3. Solve problems involving the intensity level of sound.

12.4. Solve problems involving harmonics with string instruments and open or closed-end tube instruments.

12.5. Solve problems involving the interference of sound waves (e.g., beats, shock wave).

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.

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.

19.1. (Lab) Draw, construct, and analyze a combination circuit given its description.

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.

Inspirational Syllabus Challenge

A couple of weeks ago, John Burk challenged us teachers to create more inspirational syllabi for our courses. He posted this just as I was about to send my syllabi for the fall out for copies to be made. Arrrgg!

While I don’t have visually arresting design skills, I did take another pass at my syllabi since previous versions were very dense and not at all inspirational. I wanted the revised version to share my essential goals, which I hope students find inspirational, and provide the most critical information on the first page. The details, the boring dense stuff, could be relegated to additional pages.

Here’s what I came up with for my General Physics class.

General Physics Syllabus

My Honors Physics class syllabus is very similar.

Honors Physics Syllabus

I’m going to send these out for copies before John can write another post that guilts inspires me to do more work. Hopefully, my students will benefit from these revisions as well!