UND physics lab instruction has been experiencing take data and run problems. Assessment results such as FCI or DIRECT support our observation that students are not learning much. In order to improve the situation, five years ago we had rewritten the lab instruction from procedure and data centered approach to more conceptual or descriptive form. However, the instruction lacks enforcing mechanisms to assure students’ active involvement, to make students actually read lab manuals and start thinking about lab exercises before they come to the lab . Thus regardless of considerable effort on our part the improvement was not significant.
Video capture is a direct way to acquire data from movies.
• Does not require additional machine interface.
• Web cam provides sufficient (cost less than $100) sampling rate.
(frame rate 15 to 30 per second. Select shorter exposure time to avoid blurring.
• Can take two dimensional data unlike other data acquisition techniques (photo gate, motion detector etc.)
• Seeing themselves in the video clips makes more interesting to students. Currently, an excellent inexpensive software for analysis tool is available.
• The major problem for video data taking is the distortion due to the camera angle. Even when the camera is set perpendicular to the plane of motion the distances between the camera and the object vary. However in our lab set up such distortion can be brought within the error margin.
Students work in teams with assigned roles (Manager, Skeptic and
Recorder ).
• Problems are designed to be too difficult for any individual students to
solve but not too hard for a group of students to solve.
• Context is added to the problems.
• Video capture for data taking (Mechanics Labs)
• Computerized pre-lab quizzes ensure that students have studied relevant
background material.
UND Physics and UM-Crookston are working jointly to reorganize traditional introductory Physics laboratory exercises by adapting the UMN Cooperative Problem Solving Lab (CPSL) approach: (3 year Project).
Video capture for data taking has been advocated by the UMN group. It is the most direct way of taking data. Now inexpensive web cameras are available and excellent software for digitization and data analysis are also available for minimal cost. Thus use of video capture is an attractive alternative to the traditional methods of data taking.
During the Year 1 of our current CCLI funding we have been rewriting Existing labs suitable for use of video capture for data taking to PSL form.
Comprehensive rewrite from the original PSL lab instruction developed by UMN Physics Education Research group to meet our local environment and needs. (in progress).
So far the following units are made.
Motions (1D and 2D including Drop and Shoot))
Force and Newton’s Laws of Motion
Energy (Work and Energy, Rollercoaster—under construction)
Linear Momentum
Mechanical Oscillation (SHM, Dumped oscillation Bungee jump)
Sample Questions from Friction Lab
Given a pair of surfaces what determines the frictional force?
Mass of the object?, Velocity?, Acceleration?
Analysis Questions:
Physics measurements should be repeatable. If every time you measure the results are vastly different such an experiment would not deliver a valid information. On the other hand, most of the physics measurements are statistically repeatable. Is your measurements repeatable? To what extent are your measurements significant?
Examples of Computer Screen
Hockey Puck
At the beginning of each problem context is added to promote students understanding to relate the lab exercises with real world problems.
• Standard “theory” sections are changed to guided questions about reading.
• Data tables are not provided but are created by the students before the lab.
• Ample time to fiddle the equipment before taking actual measurement is provided.
• Students are asked to predict before actually taking measurements.
• In depth analysis questions are added.
We are grateful for the generosity of Minnesota
Physics Education Group, particularly Professors
Kenneth Heller and Patricia Heller for their kind encouragement and providing helpful suggestions for our project.
The project is funded by NSF DUE-0510570 and DMR-0453518
Using shorter exposure time (1/120 s) one can get surprisingly good video of a drop and shoot experiment using inexpensive web cam (flame rate 15/sec) within 5% accuracy.
Coffee filter with small mass (piece of tape) is dropped. Due to the air drag the velocity is strikingly linear.
To model Bungee Jump a 200gr mass attached rubber bands is dropped damping effect is seen on video. The analysis tool confirms a beautifully damped harmonic motion.