AP PhysicsTeaching waves with the iPad

Learning Objectives

Students will be able to demonstrate their knowledge of wave terminology, the principle of superposition, and resonance using iPad apps.

Activity Type
These activities could be used as an introduction to the associated wave topics, or they could even be used as a form of assessment. 

Assignment Details

• Each of the iPad apps below can be used by teachers or students to demonstrate physics principles related to wave motion, the principle of superposition, and resonance. For each app, a sample activity idea is provided. Each of the apps listed in this post are free educational apps available in the iTunes App Store.
• String: This app consists of a simple string running the length of the iPad. Much like the "Wave on a string" simulation from PhET, you can adjust the properties of the string to make a variety of pulse, oscillating, standing, or traveling waves.

• Make a wave activity: Students work as individuals or in groups to create types of waves specified by the instructor. They pause the screen to demonstrate to the instructor that they have successfully created the assigned wave type. For example, students could be asked to create: one fast and one slow traveling wave, a standing wave with two antinodes, or two pulse waves headed toward destructive interference. 

• LU Wave Lab: This app acts as a virtual wave table with several different modes of operation. A simple touch on the screen can send a single 2D pulse wave in all directions or start a sinusoidal pulse oscillating.

• Characterizing interference patterns: Students use the "sinusoidal wave source" mode of the app to experiment with how the separation between two pulsing sources influences the shape of the interference pattern. Student should try a variety of source arrangements to determine a general rule that describes the shape of the interference pattern based on the placement of the sources. After discussing as a class, formalize the rule by writing it on the board. Then ask students to predict what an interference pattern would look like with three oscillating sources. 

• Fourier Touch: This app provides a wonderful illustration of the principle of superposition and Fourier synthesis. Any touch on the screen produces a sinusoidal waveform and an associated sound. The exact location of the touch on the screen influences the frequency and amplitude of the waveform. Multiple simultaneous touches produce multiple waveforms - each of their own frequency and amplitude. The sum of all of these waveforms is shown in the center of the screen.

• Beat patterns demonstration: By selecting two waveforms that are very close in frequency, this app nicely demonstrates the beat pattern that emerges. The audio generated by the two waveforms will clearly illustrate the characteristic wah-wah of a beat. By making small changes to the frequencies of the two waveforms, you can convincingly show that the beat frequency is equal to the difference between the frequencies of the two waveforms.

Instructor's Notes

• Each of these activities could be modified for a one-to-one setting or a classroom with only a single iPad. If only one iPad is available, ask a student volunteer to come to the front of the room to use the app as a demonstration. 
• In the LU Wave Lab, be sure that you modify the "mesh boundaries" setting to "MTC" to make sure that the waves don't bounce off of the walls of the simulation. 
• For further analysis of sound waves include Fourier decomposition, you may consider using the free iPad apps: oScope Lite, Octave Lite, and Fourier Lite, which use the built-in microphone to analyze sounds by creating a frequency spectrum. 

AP PhysicsChallenge Circuits

Learning Objectives

Students will build several circuits using switches and principles of series and parallel circuitry.

Activity Type
This activity would best be used as an introduction to circuits and electricity. No previous experience in electricity or circuits is required for students to complete these challenges. This activity could also be used as a practicum component to a unit test on circuits and electricity. 

Assignment Details

• Teams of students will use a variety of simple circuit equipment (batteries, bulbs with holders, wires, alligator clips, and SPDT switches) to complete four circuit challenges. 
• Circuit Challenges:

1. String of Lights: Create a string of three lights that could be used for a Christmas Tree. If one of the three lights breaks (or is loosened from its socket) the other lights should still stay on.
2. Lighting a Tunnel: Designing lights for a tunnel, you would like to be able to control two lights with one switch, which both turns on the light in front of you and turns off the light behind you. Create such a circuit. 
3. Lighting a Stairwell: In this case we want to control one light with two switches - one at the top and one at the bottom of a stairwell. Wire a circuit with one bulb in which either switch can turn the bulb on or off at any time.
4. Dimmer Switch: See if you can make a switch that would not only allow you to turn on and off a light, but also control how bright the light bulb gets. Try to create such a circuit. 

• After a team completes one of the challenges, the team must demonstrate the function of the circuit to the instructor. Then, each student on the team must draw an accurate diagram that would allow them to rebuild the working circuit.

Instructor's Notes

• The circuit challenges are listed in order of difficulty with the easiest circuit first. It is acceptabe if some of the groups never reach the last two challenges, which are particularly tricky.
• As you review the student circuits, be sure that they are not using a short in the circuit to make the light go out. Each of these circuits can be built without a short circuit. 
• Proper understanding of SPDT (single pole double throw) switches is important for completing challenges #2 and #3. The "off" position of the switch must still make an electrical connection in order for students to create these circuits.
• Students do not necessarily need to know about proper circuit diagrams before making their circuit drawings. In fact, it may be helpful for students to experience the difficulty of drawing a circuit before learning about circuit diagram conventions. 
• Creating a dimmer switch (challenge #4) will require some way to change the current of the circuit. This could be accomplished by adding more than one bulb, or by adding a potentiometer (adjustable resistance device) to the circuit. 

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).  

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 (http://www.hemispheregames.com/osmos/). 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.
  

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.