The PET curriculum provides students with a myriad of tools to help their learning. The curriculum activities are designed to elicit and challenge students prior knowledge, and to provide evidentiary support that helps students decide, if appropriate, to change their ideas.
The course pedagogy uses social interaction as a means to help students make their ideas explicit and to provide them with opportunities to consider alternative ideas. The “authority” role is shifted from the teacher to the students by having whole class discussions in which groups present ideas supported by observational evidence and the class can come to consensus. The teacher plays a supportive role, sometimes helping to clarify ideas.
In addition to using simple apparatus to conduct hands-on experiments, students also have access to some important technological tools: the MBL motion sensor and specially designed computer simulations.
The first activity in Chapter 2 provides a nice context to see the mutual and complementary roles of the hands-on equipment: the MBL motion sensor and the computer simulator. The title of the activity is Interactions and Forces (pdf). The activity introduces the idea that interactions can be described in terms of forces and elicits students' initial ideas about whether force can be transferred. In the experimental phase of the activity, students first apply successive pushes to a cart and observe its motion. Then they use the motion sensor to examine the motion of the cart in greater detail both during and in between impulsive pushes.
Following the experiments with the motion sensor, students model the same situation on a computer simulator that includes a force-time graph.
Students are shown a speed-time graph representing successive pushes to a low-friction cart moving along a track and are asked to predict how the force-time graph might look.
Then students are directed to a special simulator program. Click here to open the simulator in a separate window.
|The set-up shows a blue square that represents the cart, together with speed-time and force-time graphs.|
To start the simulation, press the Run button in the palette on the lower left of the simulation window. After pressing the Run button, you can give the cart a push by pressing on the space bar of your computer keyboard. The push will continue (at a constant strength) as long as you hold the spacebar down. To simulate successive pushes, you can press on the keyboard for a couple of seconds, then release the spacebar for a couple of seconds, then press again, etc.
The simulator stops on its own after 12 seconds. You can rewind by pressing the Rewind button, and then repeat the entire process. After practicing, you should try to duplicate the speed-time graph shown above and then compare the computer-drawn force time graph with your prediction.
From their work with the simulator, as well as with the motion sensor, students gather evidence that supports the following ideas:
the speed of the object changes only during the time a force is applied; and
when no force is being applied, the speed of the cart remains constant.
The computer simulator evidence also helps challenge the common belief that force can be transferred to an object.
Computer simulations are used extensively throughout the PET curriculum, both to support in-class activities and as part of regular homework assignments. Further examples are provided on the Sample Activities page.