The Caliper

Innovative Uses

An interesting article by Inge H. A. Pettersen (Stavanger, Norway) called "Speed of Sound in Gases Using an Ultrasonic Motion Detector" appears in the May 2002 issue of The Physics Teacher. It provides a good lesson in how motion detectors work, and on how the speed of sound varies. The motion detector is placed pointed upward inside a large bucket with a lid. Normally it reads the distance to the lid, as you would expect. But what happens if you vary the temperature of the air inside the bucket, or inject CO₂ (from dry ice) into the bucket? An original CBL was used for the experiments described, but they can also be done with a LabPro or CBL 2.

There is a very interesting article on "Bridge Swinging and the Maximum Tension in a Pendulum String" by Edward P. Wyrembeck (Howards Grove HS, WI) posted on our Vernier Idea Board. In this article, Edward and his students explain how they measure the maximum tension in a pendulum string and compare the results to the theoretical model. The Vernier Idea Board is a place for teachers and students to post ideas on how to use Vernier products that might be useful to others. Go to www.vernier.com and click on Idea Board.

The September 2002 issue of The Physics Teacher was full of articles that relate to Vernier products:

"The Hard Drive: An Experiment for Faraday's Law" by Brad Hinaus and Mick Veum (University of Wisconsin-Stevens Point) used Logger Pro and our Voltage Probe to nicely demonstrate how a computer hard drive operates.

"Interfacing Microcomputers: Back to the Future" by Marvin De Jong (College of the Ozarks, MO), has an interesting history of the early days of MBL, including early Vernier products. It also shows how to build some homemade sensors using modern equipment.

"A Friction Experiment" by Leo Takahashi (Penn State Beaver, PA) shows a way to do the friction lab in our Physics with Computers lab book in a different way with improved results.

In the October 2002 issue of The Physics Teacher, there was an article by Chris A. Gaffney and David Kagan (California State University, Chico) entitled "Beats in an Oscillator Near Resonance." In this article, they study the motion of sinusoidally-driven mass-spring system. Their experiment is a good lesson in resonance and related issues. The great thing about it is that you can drive the oscillator (a small speaker with a hook glued on) using LabPro and our Function Generator program (free on our web site).

Shelly Nash (Sioux City West HS, IA) has sent us lots of good ideas for open-ended student investigations using LabPro. She says, "One of the major things Vernier equipment does for me is allow my students to wonder about things and then make measurements regarding their scientific nature." Some of the topics investigated by her students include:

• What is the pressure at the bottom of the school swimming pool?
• How do temperature, pressure, and relative humidity vary with altitude?
• How does the force exerted on the bottoms of your feet vary as you ride an elevator? (We investigated that one ourselves in this newsletter.)

The January, April, and May, 2002 issues of The Mathematics Teacher contain three interesting "Technology Tips" from Bob Ruzich, a mathematics teacher at Fenton HS in Bensenville, IL. The January issue contains an article entitled "The arithmetic of calculus: list and the rates of change." In this tip, Bob describes a mathematical analysis of distance data collected with a motion detector to understand velocity and acceleration. The April tip is entitled "The arithmetic of calculus: sum to average value of a function area under the curve." He describes the use of a Voltage Probe to explore AC voltage and the associated RMS voltage. In the third installment, "The arithmetic of calculus: cumulative sum to velocity and distance," Bob uses an accelerometer to measure acceleration and then works backward to develop the corresponding velocity and position functions. In each of these activities, the math student uses the data to further explore the analysis features of the TI-83 Plus.