Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] Sharing a problem for students



On Dec 20, 2007, at 11:34 AM, Ludwik Kowalski wrote:

A problem for students has just been posted at

http://pages.csam.montclair.edu/~kowalski/cf/339students.html

Any comments?

One teacher suggested (in private) that I simulate the described setup. I just did this, using Interactive Physics. All looks fine to me; successive circular trajectories fall on each other. And "simulated-measured" period of one revolution is practically the same as what is expected from the imposed v=8216 m/s and R=100 m (T=0.076 s). Unfortunately, it would be practically impossible to have three nearly identical macroscopic charges for real experimentation. Simulations are desirable for this kind of situations.

Practical details about my simulation:
a) gravitational field was "off."
b) electrostatic field was "on" and "pair-wise"
The "accuracy" step was set to 1e-5 seconds. I also tried the accuracy of 1e-6 s and 1e-4 s. All of them produced the same result but simulation times were longer for shorter steps, as it should be.
P.S.
Many "what if" classroom situations can be created. For example, a teacher might ask what to expect if there is a small difference between the initial speeds. The problem could discussed and then a "simulated experiment" would be run to decide who was right and who was wrong. I used this method with the solar system (sun + 3 planets) , when I was still teaching.
_______________________________________________________
Ludwik Kowalski, a retired physicist
5 Horizon Road, apt. 2702, Fort Lee, NJ, 07024, USA
Also an amateur journalist at http://csam.montclair.edu/~kowalski/cf/