Context-rich problem for cooperative group problem solving - Electric Force
and is replicated here as part of the SERC Pedagogic Service.
This is a problem that students are asked to solve in cooperative groups during a 50 minute period. This problem occurs within the first week of studying electrostatic forces during the second semester of introductory physics for biology students. Students relate concepts from the first semester of physics, specifically forces, vectors, and free-body diagrams, to the electric force. While students work in groups of 3 or 4 to co-construct the solution to the problem, a coach who is either a graduate student or advanced undergraduate student, coaches a group as necessary.
After the groups work on co-constructing solutions and a class discussion of part of the solution, detailed solutions to the problem are handed out as the students leave.
Context for Use
Description and Teaching Materials
You are working in a lab doing research on atmospheric pollution. Your group is trying to determine what unusual types of chlorinated molecules might exist in the upper atmosphere. You have been asked to determine where a chlorine ion of effective charge -e would situate itself near a carbon dioxide ion. The carbon dioxide ion you are investigating is composed of 2 oxygen ions, each with an effective charge -2e, and a carbon ion with an effective charge +3e. These ions are arranged in a line with the carbon ion sandwiched midway between the two oxygen ions. The distance between each oxygen ion and the carbon ion is 3.0 x 10-11 m. Assuming that the chlorine ion is on a line perpendicular to the axis of the carbon dioxide ion and that the line goes through the carbon ion, what is the equilibrium distance for the chlorine ion relative to the carbon ion on this line? For simplicity, you assume that the carbon dioxide ion does not deform in the presence of the chlorine ion. Looking in your trusty physics textbook, you find the charge of the electron is 1.60 x 10-19 C.
Context-rich group problem for Electrostatics (Acrobat (PDF) 37kB Mar31 09)