This site consists of a series of interactive Java simulations that illustrate the tidal forces that occur on the oceans due to the presence of the moon. The site leads readers through a series of simulations, starting with the variations of tidal forces on a rotating earth and ending with the resulting tidal wave. This simplified model is known to oceanographers as the equilibrium theory of tides, first put forth in Newton's Principia.
Type of Material:
This material can be useful to: A. An instructor looking for lecture simulations when covering tides. B. The Physics student in mechanics class (gravitation, orbits and waves) C. The Oceanography student in geophysical fluid dynamics class.
Includes java applets created by Easy Java simulations, some users will have to update their java plug-ins before their browsers will run them.
Identify Major Learning Goals:
Students running the simulations should learn: The origins of ocean tides and their relationship with the gravitational pull of the moon and the sun. The difference in tidal forcings at different points on the earth in space and time. The effects of the horizontal and vertical conponents of those forces in the movement of water. The relationship between those forces and the standing oceanic waves that they cause.
Some knowledge of the equilibrium theory of tides and standing waves is necessary.
Overall, this is a good discussion of the origins of ocean tides and tidal currents. The simulations are very well done, including options for more or less detail, and the decomposition of vectors and waves into their compoents. Although the narratives with the applets are purely qualitative, links to a mathematical treatment of the subject are also available.
The narratives that accompany the applets are completely non-numeric and therefore suitable only for non-science majors. The mathematical discussion, however, is fairly advanced. An intermediate level, suitable for students in beginning physics courses, would also be welcome.
Potential Effectiveness as a Teaching Tool
The applets are highly effective for visualizing tidal effects, including the origins of tidal current. It clearly illustrates the rotating nature of the tidal forces on the oceans, which is hard to convey to students, even those who understand the mathematics. It follows the development of the theory from the rotation of tidal forces to the decomposition of those forces into vectors to the creation of standing waves that oscillate at the frequency of the earth/moon rotation.
The simulations and the accompanying text are descriptive, with no explanation of the background on tidal forces or mathematics involved. This requires either A) an instructor who can guide students through the concepts involved, or B) a prior knowledge of the physics involved. There is an accompanying pdf document with the author's treatment of the tidal forces, but this is at a level that would be useful only to students with a firm grasp of Newtonian mechanics already.
Ease of Use for Both Students and Faculty
Both the website and the individual simulations worked well. All controls were easy to understand and worked flawlessly. Navigation is simple and the applet controls are easy to work.
Other Issues and Comments:
This is an excellent resource. It could possibly be better with the inclusion of either simpler explanantions of what's going on for lower level students, or more of a mathematical treatment on the pages for higher level students. The issue of why these forces exist at all (in this reference frame) is one that many undergraduates have trouble understanding.
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