Monday's Lesson

Motion Two Ways

By Carolyn Staudt and Ed Hazzard

The concept of motion—the rate of change of distance and velocity over time—is a very difficult topic for students to understand. For instance, give this challenge to your students:

A car starts rolling up a ramp. It slows, stops and rolls down under the force of gravity. Graph the position and velocity of the car against time.

Because it is quite common to think that the car stops for a significant time at the top, learners regularly make a prediction that is immediately contradicted by the data. To better understand this motion, students need firsthand experience collecting the data. When they do, and the real motion of a car is represented in a graphical form, math comes alive.

Figure 1. Ramp experiment with a commercial sensor.

The Information Technology in Science Instruction (ITSI) project allows for the integration of a challenge or discovery question with instructions, data collection, and analysis, along with student input in the form of typed or drawn responses to questions. We have created over 100 activities that use probes and models for middle school physical science, earth science, and life science, and high school biology, chemistry, and physics. Most models are open source, so they can be modified. And the probes can be purchased or handmade.

In this “Monday’s Lesson,” we describe two side-by-side motion activities, one with a commercial probe and one with a motion sensor built by students using inexpensive parts.

Motion on a ramp (commercial probe)

To explore motion with your students using any of several commercial ultrasonic motion sensors, go to the following website:

www.concord.org/resources

You can preview (Show) the “Motion on a ramp” activity on the Web, but to collect and save data, click the Run link, which opens a .jnlp file to your desktop. Choose your probeware interface from the pull-down menu before running the activity (see list above). For setup, see figure 1.

Figure 2. Do-it-yourself probe electronics.

Motion on a ramp (DIY probe)

Commercial probeware is fabulous. It allows students to collect real-time data literally at their fingertips. But since some schools simply have no budget for equipment, we developed an alternative–a second motion lesson that supports a “Do It Yourself” (DIY) approach to probeware.

By creating probes used in science investigations, students learn about electronics and information technology, while also saving schools a bundle on hardware. For the cost of a $70 interface and $25 in parts, students can build simple circuits that measure temperature, light, magnetic field, motion and more than 14 different parameters in all. This requires some facility with wiring, but in return, it gives students a valuable introduction to electronics and computer interfacing (see figure 2).

Go to: www.concord.org/resources

First, follow the directions to build your own motion sensor, and then run the “Motion on a ramp” activity with your handmade motion sensor. For setup, see figure 3.

Figure 3. Ramp experiment with a do-it-yourself sensor. missing image file

Prediction and analysis

The initial challenge above asked students to make a prediction: graph the motion of a car moving up and then down a ramp. With both the commercial and the DIY probe motion activities, students are encouraged to predict the motion of the car in words and in graphical form. As students test their predictions and collect real data, the lines they draw remain as a background image on the graph, allowing students to assess how good their predictions were.

All student data is retained automatically when the activity is closed. Students or the teacher can review the data as the basis for a class discussion. A careful examination of the velocity graph shows that the effect of friction is different on the way up and on the way down. Students can also notice that “changing direction” is represented by the velocity graph passing through zero.

The final analysis of student data is a vital part of each activity. Students consider questions such as:

• What is the relationship between a distance vs. time graph and a velocity vs. time graph?
• How would you predict the velocity graph if you knew the shape of the distance graph?
• How would you predict the distance graph if you knew the shape of the velocity graph?

Students explore these questions by comparing the distance and velocity data they have collected.

Using commercial probes or building their own motion sensors, students are able to gather, analyze, model and communicate data to help them easily visualize motion. And that’s certain to get your students moving in the right direction!

Carolyn Staudt (cstaudt@concord.org) directs the ITSI project. Ed Hazzard (ehazzard@concord.org) is a senior curriculum designer.