UniServe€Science News: Newsletter of the Science Software Clearinghouse Vol. 2, November 1995

Interactive Physics II

Suzanne Hogg is a Senior Lecturer at the University of Technology, Sydney

Interactive Physics is a very powerful program, which, however, needs to be mastered by the instructor before letting the students loose on it. Documentation is good, except in the scripting language needed to write formulae to provide control of objects, customized graphs, etc. Security is impressive, if irritating. A ten-pack license means very definitely that, while twenty machines on a network may have the program loaded and `passworded', only ten may boot up. I was quite dismayed to find that I could not then extend my ten-pack to a twenty-pack, but rather had to purchase a second ten-pack license. The installation on new machines is also tiresome as you not only have to type in a long password but also have to have your manual with you so that you can answer individualised questions such as "enter the second word in the last sentence on p 61 of the manual". Operation is easy, and very predictable -- after initial teething problems, such as remembering which direction you need to drag a force or constraint so that it is not operating on thin air. Care needs to be taken in using the program in demonstration, because if the system is at all complex, the first run takes a very long time to calculate -- later runs use calculations made previously so are greatly sped up.

Special Features

i) the ability to turn gravity on and off, also create customized force fields etc.

ii) the ability to save the running simulation as a QuickTime movie, for either immediate playback, step by step, or for inclusion in other applications.

iii) the ability to show real-time vector quantities as motion proceeds.

iv) the available problem examples provided by textbook authors such as Serway, for illustrating real physical problems, which can be used as the basis for other examples.

v) it is particularly valuable in rigid body dynamics in a plane, oscillations (though calculation of period is difficult) due to springs etc.

Difficulties

i) the program does not handle well motion of, say, a point particle, on a curved surface, being constrained by its honesty in calculations -- this is good, but limiting to the lecturer.

ii) choices of velocities, masses etc. are obviously important for displaying on the screen within the view chosen. Some skill is needed in making these choices -- this is the chief reason why the lecturer needs to become familiar with the program usage and continue to be familiar with its usage.

iii) while it is possible to constrain the motion, e.g. body B starting to move 5 seconds later than body A etc., it takes practice to set this up easily.

Overall

A brilliant program in the hands of an interested lecturer, it keeps the lecturer honest in demonstrations and can be extremely valuable in demonstrating effects such as the conservation of momentum during a collision, regardless of whether gravity is `turned on' or not.

I use it as a lecturing tool in teaching Dynamics to Civil Engineers and Applied Mechanics to physics students and also have the latter students doing an exercise in rigid bodies, pinned together and rotating about each other, as an assignment. As a remedial tool I have the program mounted on three borrowable PowerBook Duos, for students taking Civil Dynamics who have not met Physics at school.

Suzanne Hogg

s.hogg@uts.edu.au

Interactive Physics v2.5

Requirements:
Macintosh 2 MB RAM, System 6.0.5+; hard disk

PC: Windows 3.1, 4 MB RAM, 368+

Price: $545. Upgrade from 2.0 $220

5 pack $995;10 pack $1495


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