Wednesday, November 16, 2011

AP Physics:
How Do Pulleys (Do) Work?

Learning Objectives
Students will explore the significance of work by experimenting with pulleys.

Assessment Type
This activity is meant to partially replace a traditional lecture on the topic of work. It can be used as a brief hands-on laboratory activity, or it can be completed using the provided simulation in an online or hybrid classroom. The purpose of the activity is to generate class discussion and is best left ungraded.

Assignment Details
  • Work is a difficult concept for students to understand, even the second or third time they encounter it. Simple machines in general, and the pulley in particular, provide excellent tools for exploring work since simple machines allow us to trade force for distance to transfer the same amount of energy. 
  • Begin the lesson by introducing the concept of work and providing students with the equation for work.
  • Without making any apparent connection to work, introduce students to the pulley. This can be accomplished with a set of physical pulley systems around the classroom (1-, 2-, and 4-pulley systems would work best). Alternatively, you can use the pulley gizmo with its 5-minute free trial. 
  • Do not over-introduce how pulleys work - simply point out that pulleys can make it easier to lift heavy objects, and that the more pulleys there are, the easier it is to lift the object.
    • Pose this question to students: How can simply adding pulleys make something lighter?
    • Ask students to work in teams of 2-3 to investigate this question and write out their explanation (including a drawing) on a white board or sheet of paper. 
    • When students are complete, ask a few groups to share their work with the class and discuss.

    Instructor's Notes
    • To make the investigation more quantitative, provide students with force meters and meter sticks. Students should be able to show that the same amount of work is done with each pulley configuration. 
    • A good transfer of knowledge question (in class, on homework, or on a test) would be to ask why pushing a cart up a ramp is 'easier' than lifting it straight up. You could follow up by asking whether we measure the difficulty of a task by the amount of work required or by the force required (the answer is not trivial).  

    Sunday, October 16, 2011

    AP Physics:
    Is Momentum Conserved in Osmos?

    Learning Objectives
    Students will design an experiment to determine if momentum is conserved in the video game Osmos.

    Assessment Type
    This activity can be used as a formative assessment, extracurricular project, or challenge problem for advanced students. There are multiple methods that could be used to answer the question. The ultimate goal is to promote student creative thinking and problem solving.

    Assignment Details
    • Students should begin by downloading and installing the free demo of Osmos, which is available on a variety of platforms including Windows and Mac computers ( Osmos is also available for purchase through the iTunes App Store for iPad, iPhone, and iPod Touch.
    • Students should experiment with the game to learn how it works. In particular, students should recognize how the conservation of momentum is essential to motion within the game. 
    • Students are challenged to answer the following question: Is momentum conserved when the mote propels itself? 
    • Students are asked to design an experiment to answer this question. In particular, they must clearly outline: 
      • The process they followed to reach their conclusions.
      • The data they collected
      • The assumptions they had to make.
      • The calculations they performed. 
    • Students should submit their solution in the form of a 2-page report or a 2 minute video. 

    Instructor's Notes
    • In order to answer this question, students will have to wrestle with these additional questions:
      • How does the mass of the player mote compare to the mass of the expelled mote?
      • How can we determine the velocity of the motes?
      • Do we need to know the absolute velocity or will relative velocity suffice?
    • You may recommend that students use video analysis software to collected data on motion within the video game. By using a combination of screen capture software (such as Jing) and video analysis software (such as Tracker) students can extract numerical data to draw their conclusions.
    • A few well-timed screenshots could also be used instead of video analysis to measure the recoil of each mote and ultimately answer the question. 
    • The following could be used as a simple rubric for evaluating this student project:
    • (10 pts) - Process for solving the problem is clearly outlined and accurate
      (5 pts) - Assumptions are appropriate and data is collected
      (5 pts) - Calculations are accurate and solution is correct.

    Thursday, September 15, 2011

    AP Physics:
    Newton's Laws in Three Pictures

    Learning Objectives
    Students will be able to recognize Newton's Laws of Motion in ordinary situations.

    Assessment Type
    This activity can be used as a formative assessment to check student's conceptual understanding of Newton's Laws of Motion.

    Assignment Details
    Ask students to go around the school, looking for examples of Newton's Laws of Motion. When they find a situation that illustrates one of Newton's Laws, students should take a photograph using a digital camera (cell phones would work fine).

    After returning to the classroom, students should write a brief description of how each image illustrates one of Newton's Laws. For example, a student description for the images above may look like:

    1st Law:
    A stapler is sitting on a desk illustrating that objects at rest will stay at rest.

    2nd Law: When pushing someone on a swing, a greater force must be applied to someone with a greater mass in order to achieve the same acceleration.

    3rd Law: When the hamster runs in his wheel, there are two forces between his feet and the wheel -- one pushing his feet forward and the other pushing the wheel backward.

    Instructor's Notes
    Students can use one of several free online tools to create an animated .gif of their images (as above). The student's work can then be added to a class website, showing all the different ways Newton's Laws can be found in everyday life.

    This same activity can be used to check student understanding for a wide variety of conceptual topics in AP Physics. For example, conservation of momentum, oscillations, refraction, and resonance would all make for an interesting series of photos.

    As a formative assessment, this activity could be graded on a completion basis. Rewards, such as placing the best examples on the class website, could be used to motivate students toward excellent work.

    Monday, August 15, 2011

    AP Physics:
    The Kinematics of Plants vs Zombies

    Learning Objectives
    • Students will be able to apply equations of motion to the video game, Plants vs Zombies

    Assessment Type
    This lab activity asks students to use video analysis software to address several questions related to the motion of zombies in the popular video game, Plants vs Zombies. This activity could be used as a formative or summative assessment of students' knowledge related to constant-velocity motion. It could also be used as an introductory review activity for AP students prior to starting the first unit.

    Assignment Details
    • Before beginning this activity, students should download and install the required software:
    • Tracker: This is a powerful open-source video analysis tool for physics teachers. It makes a great free alternative if you do not have Vernier's LoggerPro software, which can also perform the same video analysis.
    • Plants vs Zombies: While the video snippets needed for this activity can be downloaded below. It will be helpful for students to have some experience with the actual game. It can be played in the web browser or downloaded as a free demo.
    • The activity can be presented to students as a series of questions. Students are directed to collect data that clearly and convincingly answers the following questions.
    • Question 1: Does the pea shooter slow down the zombies?
    • Question 2: At what position and time will the javelin-carrying zombie pass the cone-wearing zombie?
    • Question 3: By how much does the frozen pea shooter slow down the zombie?
    • Students will create a lab report or a brief video that presents their data, describes their analysis, and explains their conclusion.

    Instructor's Notes
    • If you have screen recording software available, you can ask that students make their own videos for analysis, otherwise students can use the following videos to address each of the questions.
    • Question 1 Video
    • Question 2 Video
    • Question 3 Video
    • Students could be assigned to answer all three of the questions or given the option of choosing just one question to answer. Question 2 is the most open ended and would require students to make careful choices regarding their frame of reference for measurements.
    • Students can compare their prediction in Question 2 to this video, which shows the javelin-carrying zombie passing the cone-wearing zombie.
    • The following could be used as a simple rubric for evaluating this student activity:
      (10 pts) - Clear and convincing conclusions are drawn that are consistent with the data
      (5 pts) - Data analysis is correct and appropriate for the question being addressed
      (5 pts) - The data was collected accurately and illustrates the motion shown in the video.

    Friday, July 15, 2011

    AP Physics:
    The Physics of Osmos

    Learning Objectives
    • Students will be able to recognize and explain physics concepts in novel situations.

    Assessment Type
    This activity asks students to recognize physics concepts within the video game Osmos. Students are then asked to use the video game to demonstrate and explain the concept that they have identified. This activity can be used as a formative assessment of student understanding or as a summative assessment after a comprehensive introduction to kinematics or momentum.

    Assignment Details
    • Students should then download and install the free demo of Osmos, which is available on a variety of platforms including Windows and Mac computers ( Osmos is also available for purchase through the iTunes App Store for iPad, iPhone, and iPod Touch.
    • Students will experiment with the game, looking for physics concepts that could be demonstrated using the video game as their laboratory.
    • Using screen capture images or free video screen capture software (such as Jing:, students can create their own video demonstration and post it to YouTube as a response to the original "Physics of Osmos" video.

    Instructor's Notes
    • There are a wide variety of concepts that can be demonstrated with this game. If students' need help identifying possible topics, direct them toward: Newton's 1st, 2nd, or 3rd law, elastic collisions, inelastic collisions, conservation of momentum, or rocket propulsion.
    • Using later levels of the game, students can also explore gravitation and orbits, these levels could be used as a demonstration of Kepler's Laws, uniform circular motion, or simple harmonic motion.
    • As a possible follow-up to this activity, include screenshots from Osmos on an end-of-unit test or final exam. Ask students to solve a problem involving the glowing orbs or to explain a concept in the context of the game.
    • The following could be used as a simple rubric for evaluating this student project:
      (10 pts) - Physics concept is named and explained in the video
      (5 pts) - Concept is convincingly demonstrated using the game
      (3 pts) - Video is clear, concise, and easily understandable
      (2 pts) - Student showed creativity or insight in their demonstration

    Tuesday, June 14, 2011

    AP Physics:
    Air and Fluid Pressure Activity

    Learning Objectives
    From Chapter 7 of AP Physics B
    • Understand and apply the relationship between pressure and depth in a fluid.

    Assessment Type
    This activity challenges students to explain very familiar phenomena using the concept of fluid pressure. In the process, even advanced students will have their misconceptions about pressure revealed. This activity can be used as a formative assessment of conceptual understanding or even as "practicum" component on a test or quiz.

    Assignment Details
    1. Provide students with a few basic supplies: 5-10 plastic straws, a small cup filled with water.
    2. Ask students to perform the following three experiments and record their observations as well as a detailed explanation using the concept of pressure.

      Experiment 1: With the straw only in air, place a finger over the top of the straw, closing the top end off. Put the bottom end of the straw into the cup of water and record your observations and explanation.

      Experiment 2: With the straw open on both ends, put the straw halfway submerged into the water. Place a finger over the top of the straw, closing the top end off. With a finger still over the top, remove the straw from the water and record your observations and explanation.

      Experiment 3: Make an extra long straw by connecting two straws together in a chain. Place the straw in a cup of water and attempt to move the water up the straw to your mouth with a single long and constant draw. If you are successful in getting water all the way to the top, then add another straw to your chain and try again. Find the highest straw length where it is no longer possible to move the water to your mouth with a single constant draw. Record your observations and explanation.
    3. Allow the students to experiment, providing as much autonomy as possible and trying not to influence their observations or explanations.
    4. After students have completed the experiments, ask them to share their observations by facilitating a class discussion. Go through each experiment one-by-one, with students sharing their observations and then discussing their explanations of the results.
    5. Use leading questions to correct misconceptions and always return to the experiment when there is disagreement about what actually happened.
    6. As a final test of their understanding ask students if there is an absolute limit to the height of a usable straw (even if a machine used the straw instead of a person). If so, what would cause this limitation? and how high would the maximum height be?

    Instructor's Notes
    • Each of these experiments demonstrates the strong influence of air pressure. Students will be tempted to explain the experiments in terms of "vacuums" and "suction." Feel free to forbid the use of these two terms at the start of the lesson.
    • When "sucking" water up the straw, be sure that students keep the straws vertical, so that they do in fact reach a limit. Students will reach various limiting heights with their straws. This height is limited by the degree to which the pressure in the straw is lowered below atmospheric pressure. In some sense, this height can be used as a measure of lung strength.
    • The absolute limiting height up to which a straw can be used is determined by atmospheric pressure. The pressure caused by the weight of the column of air above the surface of the water can push the water up the straw until the weight of the fluid in the straw matches that of the column of air. Estimates on a numerical value for this height can be performed using the densities of air and water as well as the approximate column height of the atmosphere.

    Sunday, May 15, 2011

    AP Physics:
    Free-Fall Motion Inquiry Activity

    Learning Objectives
    • Understand and apply the principle of free-fall motion in a uniform gravitational field.

    Assessment Type
    This inquiry activity is a wonderful launch point for a discussion on free-fall motion and particularly the non-negligible role that air resistance play in free-fall acceleration. The activity can also be used as a formative assessment of students' abilities to design an experiment, generate and test a hypothesis, and make careful observations.

    Assignment Details
    1. Provide students with just a few basic supplies: manilla folders, empty film canisters, and pennies.
    2. Ask students to collect data using these simple tools to answer the following two questions:
      a) Does mass impact the rate at which objects fall?
      b) Does shape impact the rate at which objects fall?
    3. Allow students to experiment, provide as much autonomy as possible and try to accommodate student requests for other resources (rulers, timers, tape, etc) as they carry out their experiments.
    4. After students have experimented for some time, ask them to share their conclusions by facilitating a class discussion. Any statement made by a student or group should be confirmed by a simple experiment shown to the class.
    5. Through the process of testing one another's conclusions, work with the students to generate a statement describing the conditions under which mass and shape seem to impact the rate at which objects fall, being sure that everyone agrees to the language used.
    6. As a final test of their conclusions, choose two new objects that the students have not experimented with -- say a styrofoam cup and a plastic cup. Ask the students to discuss which would hit the ground first when dropped from the same height, and under what conditions the opposite result could be achieved.

    Instructor's Notes
    • Physics instructors often teach students that mass does not impact an object's free-fall rate. While this is true in the absence of air resistance, it is not true under normal circumstances. This activity can be used to demonstrate why Galileo's understanding of free-fall motion took thousands of years to emerge.
    • The joy and challenge of this activity is the open nature of the experimentation. Allow students to pursue experimental dead ends and even to make incorrect conclusions from their experiments. Through the class discussion, students will confront their misconceptions and be forced to reconcile them with the experimental evidence.
    • This activity can be used as an introduction to free-fall motion, before the simplifying assumption of ignoring air resistance is made. It could also be used after free-fall motion has been studied in detail and as an introduction to friction and/or terminal velocity.

    Friday, April 15, 2011

    AP Physics Exam Review:
    Physics in the News

    Learning Objectives
    • Conduct a review of the topics discussed throughout the year.

    Assessment Type
    This review activity serves the dual purposes of reviewing physics concepts and applying this knowledge to current events in world news. This activity would be used as a formative assessment as well as a break from the traditional review routine.

    Assignment Details
    1. Students begin by searching various new sources to explore current events. Helpful resources could include Google News, Wired, Scientific American, or USA TODAY.
    2. Students find an article that is related to a physics concept they learned this year.
    3. Students write a brief description of the news article.
    4. They explain what makes physics relevant to this story, using specific examples of physics concepts they learned in class.
    5. Students create an AP Physics review problem related to the news story that they chose.
    6. Students write the complete solution to their problem.
    7. The student-written problems are redistributed around the classroom, and students try to solve a classmate's review problem, checking their solutions when finished.

    Instructor's Notes
    • Consider redistributing the student created problems two or three times for additional practice and review.
    • To increase the incentive for creating a quality review problem, tell them that you will include one of the question they create on the final exam.

    Students can be assessed on the following criteria.
    1 pt - Students provide a concise and clear summary of the news article.
    3 pts - Students correctly describe a physics concept and make a reasonable connection to the article.
    6 pts - Students create a problem related to their news story that is of suitable difficulty and include a complete and correction solution.

    Total = 10 pts

    Sunday, March 13, 2011

    AP Physics B:
    Exploring Models of the Hydrogen Atom

    Learning Objectives
    • Explain qualitatively the origin of emission or absorption spectra of gases

    Assessment Type
    This activity can be used to introduce atomic models and serve as a formative assessment of students' understanding of alternate models of the Hydrogen atom.

    Assignment Details
    1. Direct students to the "Models of the Hydrogen Atom" simulation from PhET.
    2. Click "Run Now" to begin the simulation.
    3. Ask students to explore the various atomic models under the prediction setting, trying to decipher what distinctions can be made between the models.
    4. Students, working in pairs, should examine at least three atomic models in detail (Bohr's model and two others of the students' choosing). Student pairs are asked to discuss the models and create a two-to-three sentence description for each of their three models explaining how the model can be employed to explain the emission of light.
    5. Ask students to turn on the spectrometer and collect spectral data for each of their three atomic models.
    6. Students should then compare the spectra from the three models, and record at least one similarity and/or difference between each pair of models that they observed.
    7. Turning the dial to "Experiment," students can collect spectral data on a 'real' Hydrogen atom.
    8. After sufficient data is collected, the students will compare the experimental data to the predictions of their three models and rank them from most accurate to least accurate.

    Instructor's Notes
    • Use the slider at the bottom of the simulation to make time go faster, making it possible to collect data more quickly.
    • Encourage students to use the camera button on the spectrometer to record their spectral data sets.
    • Ask students to speculate why the spectra from each model differ in the ways they do.
    • A particularly worthwhile discussion could be focused on the relative merits of the Bohr and deBroglie models.

    Students can be assessed on the following criteria.
    6 pts - Students provide accurate two-to-three sentence descriptions for each of their three atomic models.
    3 pts - Students correctly describe at least one similarity and/or difference between each pair of models they observed.
    1 pt - Students properly rank their three models in order of accuracy.

    Total = 10 pts