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Teaching Tips and Techniques:

These are the tasks involved in implementing this module. This page also provides questions for you to guide students in the building an analysis of their STELLA models. Most science students are familiar with the scientific method used in the inquiry-based lab, but might need assistance working with computer modeling tools, like STELLA. Students need a basic knowledge of spreadsheets, or else, an introduction to spreadsheets should be added to this module. Also provided is our sample STELLA model for the motion of a pendulum.

Resources:

Off-line:

On-line:

Acess to computer connected to the Internet

Teacher Tasks:

  1. The teacher poses a question: What are the factors that affect the period of a pendulum?
  2. The teacher will define period as the time required for a pendulum to swing through one complete cycle.
  3. In lab groups the teacher will instruct students to choose 3 relevant factors (variables) that affect the period.
  4. The teacher will monitor groups and assist as needed in choosing appropriate variables.
  5. The teacher will direct students to form hypotheses (predictions) about the effect of the chosen variables.
  6. The teacher will then direct students to conduct a physical experiment to test their hypotheses.
  7. After students conduct their experiments, the teacher will review basic Excel spreadsheet skills, if necessary.
  8. The teacher will direct students to analyze their data using Excel.
  9. If necessary the teacher will present basic Stella instruction.*
  10. Teacher will guide students through building a Stella model of a pendulum.

*We suggest the Deer Population and the Flow Rate STELLA models used to introduce students to STELLA were created by teachers from the Maryland Virtual High School.

Here is a SAMPLE STUDENT LAB with RUBRIC for the inquiry-based laboratory and the spreadsheet analysis.

Questions to Guide Students in Building the STELLA model:

  1. What quantities are changing when the pendulum swings? (These are the stocks.)
  2. What are the quantities that cause the change in the stocks? (These are the flows.)
  3. What quantities affect the rate of the flows? (These are the converters.)
  4. What building block is used to indicate that changes in one element cause changes in another element?
  5. What equation should be used to determine the angular acceleration of the pendulum?
  6. What quantity should be displayed on the graph in order to compare the period for various lengths?

Questions for Analysis of the STELLA model:

  1. What is the effect of the length on the period of the pendulum?
  2. What is the effect of the length on the angular velocity of the pendulum?
  3. What quantity in the model is represented by the amplitude of the graph?
  4. What quantity in the model is represented by the wavelength of the graph?
  5. What is the effect of the length on the angular acceleration of the pendulum?

STELLA Model

MAP/MODEL LEVEL EQUATION LEVEL
The STELLA Pendulum Model

STOCK:
Angle(t) = Angle(t - dt) + (- Change_in_angle) * dt
INIT Angle = Initial_Angle_in_Radians
OUTFLOWS:

  • Change_in_angle = Angular_Velocity

    STOCK:
    Angular_Velocity(t) = Angular_Velocity(t - dt) + (- Angular_Acceleration) * dt
    INIT Angular_Velocity = 0
    OUTFLOWS:

  • Angular_Acceleration = Gravity*sin(Angle)/Length

    CONVERTERS:
    Gravity = -9.8
    Initial_Angle_in_Radians = 1
    Length = 25


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