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Bruce C. Palmquist
Professor
palmquis@cwu.edu
Department of Physics / Department of Science Education
Central Washington University
Sorting Trash with Static Electricity 

Recycling plastic is an effective way to reduce waste in landfills. However, in order to effectively reuse recycled plastic, different types of plastics must be separated from one another. This is a time intensive task. Engineers in Japan have tested a way to separate plastics using static electricity. In this interrupted case, students will design a method to separate plastics using static electricity, make hypotheses based on what the Japanese engineers did, and analyze their actual data with a focus on bar graphs. The case can be used as a course transition from electric charge to electric fields. Students should have prior knowledge about the triboelectric series and Coulomb's Law; they should also be familiar with the basic kinematic equations for objects moving with constant acceleration. Although originally developed for an introductory calculus-based physics class, calculus is not required, and so the case can easily be used in an algebra-based college physics class or even a high school physics class that covers static electricity concepts.


The Itsy-Bitsy Spider: An Analysis of Spider Locomotion 

The evolution of physiological characteristics can be strongly influenced by physics. Animals whose physiology allows them to better escape predators will live longer, on average, and be more likely to pass on the genes that led to these favorable traits. In this interrupted case study, students design a method to compare the motion and leg characteristics of different spiders, make hypotheses based on the actual experiment, and analyze the scientists' actual data and scatter plots. Since spider locomotion can be modeled as three different types of pendulums, this case can be used as an application activity following a unit on pendulums or energy conservation. The case was originally written for an introductory calculus-based physics class; however calculus is not required for the analysis, so this case would also be appropriate for an algebra-based college physics class or even a high school physics class that covers pendulum motion and energy concepts.