SciGen Teacher Dashboard
Unit E1
Potential and Kinetic Energy
Lab: Rubber Band Energy
Duration: Approximately 50 minutes
This lab is an investigation of the relationship between kinetic energy and potential energy. Students will measure the kinetic energy released by a stretched rubber band.
LEARNING OBJECTIVES
Students will look for an observable relationship between kinetic energy and potential energy.
Teacher Tips
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The actual energy transfers during the experiment consist of:
- a) storing potential energy in a rubber band;
- b) releasing it as rubber-band kinetic energy;
- c) transferring a fraction of that kinetic energy from the rubber band to the half-cup, and;
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d) dissipating the half-cup kinetic energy by air and surface friction.
- The relationship of rubber-band extension to potential energy is quadratic, and the relationship of half-cup movement to kinetic energy is not easily modeled. If the goal is to connect the potential energy of a spring to kinetic energy, that connection is implicit in the fact that the rubber band moves when it is released; one could simply shoot it upward and see how high it goes if a quantitative test is wanted.
Materials (per group)
- a rubber band
- a paper cup sliced in half lengthwise (plastic and Styrofoam cups can also work)
- a ruler
Safety Checks
- Review with your students all your school's safety protocols when doing labs.
- Rubber bands should be pointed only inside cups.
- Cups should be positioned so that no student (or teacher) can get hit by wayward rubber bands that miss their targets.
- Flying rubber bands can cause injuries, especially to eyes. Consider protective goggles.
Teacher Tune-ups
Teaching Notes
ACTIVITY OVERVIEW
- Set-up (10 minutes)
- Conduct tests and gather data (20 minutes)
- Graph and discuss findings (20 minutes)
Set-up (10 minutes)
Have students work in pairs or small groups. They should agree how far to stretch the rubber band for each of the 3 conditions and then carefully extend the rubber band the determined distance. The lab requires that students conduct three trials for each condition. Students record how far the Styrofoam cup moves and calculate the mean movement for each condition.
You will need:
- a rubber band
- a cup sliced in half lengthwise
- a ruler
Here is how to cut a cup in half lengthwise:
Conduct tests and gather data (20 minutes)
Review the testing procedure with students. A lab worksheet is provided, or you may have students work in their own notebooks.
Procedure:
- You will stretch your rubber band to three different lengths – short stretch, medium stretch, and long stretch. Each length of the rubber band is a “condition” of your experiment.
- Conduct 3 trials for each condition.
- For the 3 trials for each condition, make sure the rubber band is stretched exactly the same length and that the cup starts in the exact same place.
- Carefully aim the rubber band at the same spot on the cup (so the cup will move in the same direction).
- Record how far the cup moves for each trial. Then calculate the mean distance for each of the 3 conditions.
Graph and discuss findings (20 minutes)
Line Graph
Bar Graph
Scatter Plot
After students determine the average for each condition, instruct students to display the data on a graph. Students could make a line graph, bar graph, or scatter plot. Hypothetical examples of each are provided. Traditionally the dependent (outcome) variables are graphed on the y axis.
:
- Do you see a trend in the points or bars that you plotted?
- Does the data support ideas about how potential and kinetic energy are related in this simple system?
- Where on the graph is potential energy greatest?
- Where on the graph is kinetic energy the greatest?
BETA Version - Please send comments and corrections to info@serpinstitute.org
This project was supported by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science.
Strategic Education Research Partnership
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info@serpinstitute.org