Peer Review

The Pendulum Lab

Material Detail page

Bookmark

Overall Rating:

Content Quality:

Effectiveness:

Ease of Use:

Overview:: A collection of virtual experiments based on a simulation of a driven pendulum. Covers undamped and damped motion, drive options include a periodic forces and horizontal, vertical, and rotating pivot drives. A stopwatch is available for quantitative measurements for the undriven case, an oscilloscope is used for the others. Operating parameters can be varied by the user. Each of the systems covered includes some suggested experiments. There are also extensive links to discussions of the underlying theory in the associated lecture room. The latter is very detailed, with extensive definitions of fundamental concepts. This is particularly welcome in the discussion of non-linear dynamics.
Type of Material:: Simulation with additional reference material on the underlying theory.
Recommended Uses:: In-class demo or homework assignment
Technical Requirements:: Uses Java Applets
Identify Major Learning Goals:: Students can explore topics in periodic and non-linear dynamics. Since the lab has extensive depth, either basic or advanced properties of motion may be studied.
Target Student Population:: Lower and upper division undergraduate majors in science, math, and engineering.
Prerequisite Knowledge or Skills:: A basic understanding of simple harmonic motion at the introductory physics level. Some knowledge of differential equations is needed for the advanced material.

Rating:
Strengths:: This site is a very comprehensive treatment of pendulum motion. It is noteworthy in that it includes both traditional material in introductory dynamics as well as discussions of recent results from non-linear dynamics. It includes simple cases appropriate for the introductory level as well as more complex activities (e.g. chaotic motion) suitable for advanced students. Parameters can be varied in a simple yet comprehensive manner.
Concerns:: In the initial undamped, undriven pendulum theory section, the figure displaying forces omits the tension force, considering only forces tangential to the circular motion. Also the description of "m * a" as the inertial force is unconventional and perhaps confusing.

The damping term used throughout is linear in the angular velocity, to model damping due to the viscous medium. This is not accurate for the cases where the pivot also moves. In such cases the damping term is also a velocity dependent torque acting at the pivot.

Because the simulations are somewhat simplified models, the user can place the pendulum in an unstable equilibrium. This is not possible for real experiments, of course.

Rating:
Strengths:: Each lab includes suggested experiments designed to illustrate the concepts under consideration. Extensive links from the lab pages to the lecture room offer in-depth discussion of the underlying physics. The greatest impact for student learning might be the use of these labs for an upper level mechanics or computational course, as a hands-on supplement to a standard textbook.
Concerns:: Persistence of the trace on the oscilloscope is not adjustable. This makes it difficult to observe relevant features of phases diagrams for non-linear cases.

Rating:
Strengths:: The simulation is easy to use, and the related supporting content is easy to find, but also does not clutter the main investigative area.

The entire package can be downloaded for local use in a compact archive file.
Concerns:: A minor quibble is that the list boxes that control oscilloscope scaling are not labeled to indicate their function. This should not be a major problem given the intended audience, however, instructors using the applet might wish to point this out when making an assignment. Also, some of the animation display areas are quite small, perhaps making visibility difficult when the simulation is used in a classroom demo.

Other Issues and Comments:: This is a unique example of combining theory and simulation into a tightly-knit package. It enables exploratory learning for a subject and advanced level where it is rarely done.
Creative Commons: