There is virtually no physics in it, but here's something you
might find of some small value: It's a software timer.
-- It will count down and alarm when it reaches zero.
-- It will count up.
-- It displays HUGE easy-to-read digits on the screen.
-- You can use it as a stop watch, with arbitrarily many split times.
-- The splits have millisecond resolution, and probably ~20ms accuracy.
Free, libre, open-source, public domain, cross-platform javascript.
Obviously no warranty. Tested on Firefox (Linux) and Chrome (Android).
Probably works on other platforms. Try it online, then download it
for offline use.
Uses include:
*) Timing random events around the lab. The easy-to-use
split-timer function comes in handy.
*) Timing students' practice talks.
*) Timing talks at actual scientific meetings. There are
always a few guys who think the rules don't apply to them.
Having an actual audible alarm go off encourages them
to finish on time. Easy-to-read digits makes it easy
for them to know the score.
*) Ditto for political candidate forums. A /lot/ of these
guys think the rules don't apply to them. If they ignore
the nice bell sound, you can escalate to the "gong" sound
and/or the "cuckoo clock" sound.
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BTW I still do not encourage introductory-level students to
write in javascript. It's too low-level. Learn to program
in a modern high-level language first.