Making Sense of Motion
by Bob Coulter
As our students grow up in an increasingly digital age, keeping them grounded in the fundamentals of physics can be quite a challenge. With real experience being replaced by electronic representations, kids' intuitive sense of how things work can be altered in ways that may not be productive. Examples of this abound in video games as the laws of physics are suspended to make a good game. Players leap from place to place toward a goal, or water droplets change phase from solid to liquid to gas as needed to solve a puzzle. Even if the physics within the game are realistic, there is a world of difference for young learners between seeing a screen representation of a ball being hit and having the experience of hitting one.
One tool to consider in bridging this gap between experience and representation is an electronic motion sensor. With the use of a sensor, students' motion shows up on the computer screen, allowing them to link their bodily-kinesthetic experience with a graphic representation. Probes like this have been used for more than a decade in schools, but they have often required expensive and somewhat cumbersome sets of equipment. Newer models provide a relatively inexpensive alternative with easy setup and a kid-friendly interface.
Data collection on the Go!
For these examples, I'll be using Vernier's Go! Motion probe, part of their Go! series of probes. In addition to the motion probe, others in the series include a temperature probe, magnetic field sensor, and a force plate. (Other probes can be added with an adapter.) Each of these Go! probes comes with basic data collection software and a probe that automatically links to the software. All you need to do is plug the probe into a USB port and start the included Logger Lite software. You're literally ready to start collecting data in secondsno elaborate setup or calibration is required.
The probe collects data by sending out sound waves and "catching" their return when they bounce off an object. A simple introductory activity might involve having a student walk back and forth in front of the probe, noting how their motion is displayed on the screen. As they move away from the probe, their position is recorded higher on the graph; as they move closer, the line on the graph decreases. Once they "get" how the probe records motion, students can use the Predict tool to draw a line on the screen and then try to walk the line. It's not as easy as it sounds! With a couple of tries, they can forge a link between their actions and how they are recorded. As an added bonus, students are also building critically important graph-reading skills as they interpret their data and adjust their motion to match the target line they drew.
Extending the experience
One extension of this activity can be found in the optional Elementary Science With Vernier curriculum guide. Once students have a good understanding of how the probe works, they can write directions to replicate certain patterns in the graph. For example, the directions could tell someone to start 2 meters from the probe, wait 3 seconds, and then move slowly back for 2 seconds, reverse course, and move quickly back to the starting point, and so on. Activities such as this deepen understanding of the tool and build language and math skills in the creation and refinement of the directions.
From here, you and your students can explore more advanced concepts such as periodic motion. If you rig a simple pendulum so that it moves back and forth in front of the probe, students can track the motion of the pendulum back and forth. The trick in doing an investigation like this is to have a large enough target for the sound waves to hit. A balloon-sized target will give you better results than a smaller one, but in either case you will likely get some "noise" in the data. These odd spikes in the graph present a good opportunity to discuss what has happened and why the distance seems to have suddenly jumped. For example, one possibility for a suddenly higher reading might be that the probe missed the target and hit the wall further away from the pendulum.
Adding math to the study
To build a more mathematical dimension to your study, students can measure how many seconds pass between each swing. That data can be collected directly from the table (at the left of the Logger Lite screen), or from the graph itself. By clicking the "Examine" button, students can get the reading at any point in the graph. By gathering the time data for successive high or low points, the period of the pendulum can be calculated. Additional math angles that come from this investigation include looking at the data table to determine how you know the pendulum has shifted direction, and interpreting the velocity readings that are negative numbers. Over time, your students will become increasingly comfortable linking movement they observe with the associated graphic and numeric representations.
Moving forward, a number of additional studies become possible. Your students will have many ideas, but if you're looking for more, the Elementary Science With Vernier book suggests other periodic motion activities, such as having a Slinky bob up and down over a probe pointed upward, and using the probe to mimic bat sonar. In that project, students can act out the role of different insects trying to avoid capture. If you work with older students, you might find activities in the Middle School Science With Vernier book helpful. These include investigations of velocity based on measuring cars on a ramp, studies of falling objects, and measurements of classmates sliding down a playground slide. All of these projects help your students to develop a strong basis for understanding formal physics later in their school careers.
©2009 Synergy Learning, Inc. All rights reserved.
Vernier Data-Collection Technology for computers and handhelds: Find the easy-start package for GO! probes as well as over forty other probes that can connect to your computer. Go! products are Windows and Mac compatible. 888-837-6437. http://www.vernier.com/go.
- Bob Coulter is director of Mapping the Environment, a program at the Missouri Botanical Garden's Litzsinger Road Ecology Center that supports teachers' efforts to enhance their science curriculum through the use of the Internet and geographic information system (GIS) software. Previously, Bob taught elementary grades for 12 years.