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Tuesday, May 20, 2008 - 03:29 SGT
Posted By: Gilbert

Holidays, Week One

Work

Where should I start? For the first time I've been tied up with a job for the full three months of the summer hols (no, fulfilling my deferment obligations for NS doesn't count), but it's not exactly a conventional internship. It's the Computing for Voluntary Welfare Organizations (CVWO) stuff that sel has been involved in for awhile, and the actual computing (coding) is done from home. Telecommuting saves unneeded transport fees and other resources, so it's win-win both ways.

Quite a few meetings for the first week to get started with, though, but as the hours are certainly shorter than the typical 9-to-5 gig I can't complain. Then again time has never really been the point with programming - I mean, if one can complete an assigned task according to specifications in two hours instead of eight, there isn't really any point sitting around pretending to look busy.

While the sort of system engineering needed isn't anything I haven't done before (in the software engineering module, as well as long ago in my NS days when one of my platoon mates suggested some online inventory system and I hacked it out in Perl in-camp, but that's another story), it'll be my first real-world project that isn't some way about myself. Never found content management platforms like Drupal necessary, but now that there will be multiple coders I suppose some sort of control becomes helpful. It appears that they have got a packaged WAMP server for Windows nowadays too - it seems so long ago that Jiaqi introduced me to ActivePerl + Apache back during NS for said online inventory system, heh.

Got to visit a couple of welfare organizations that I would otherwise likely never have gone to, such as the Christalite Methodist Home (for the socially disadvantaged elderly) and the SIA-MINDS (Movement for the Intellectually Disabled of Singapore) Employment Development Centre. By the way I can't be said to be doing charity, since I do get a decent (corporate-sponsored) stipend out of this - but from what I've heard about the prices that external vendors charge for commercial IT solutions, they should at least get their money's worth.

The people-interaction part isn't exactly under our job scope, but from initial observations the centres are all... very organized. Then again, this is Singapore. The MINDS visit in particular opened my eyes - one chap with crossed eyes and buck teeth turned out to be a very confident speaker with a good voice to boot, and I wouldn't know how to knit like one of the "intellectually-challenged" ladies did. The handphone pouch was of pretty exquisite workmanship. The Japanese drumming performance they put up was quite professional too.

Media

Caught up with a couple of movies and books too. My cousin got Gladiator and Harold & Kumar Go to White Castle (released in 2000 and 2004 respectively) on DVD, so I finally came around to watching them. (The joy I will have when I am retired! All those films to watch!) Oddly enough, I had already been introduced to some of the gags in Harold & Kumar through the Kingdom of Loathing gameplay, but at least I don't remember going through the plot on Wikipedia for either, unlike with some movies that I reckon that I would never watch even when retired. One thing though - I am now resolved to try out a White Castle slyder before getting my Great Reboot From The Sky.


Current fav Bleach character - Zaraki Kenpachi (KFC image source)

Finished browsing through Bleach on OneManga too. As with Naruto, I got hooked after previously deriding it as mass-market fare. Better not get started on any other manga for now, argh.

Tennis

Tried my hand at tennis with Edchong, Alvinny & Alvinny's friend on Wednesday night at the NUS SRC courts.

Lesson Number One: Remove plastic covering of racket grip to prevent flying racket.

Lesson Number Two: Tennis strokes are very different from badminton strokes. Hitting a tennis ball badminton-style generally results in it going into the net (as a tennis ball is somewhat heavier) or flying over the fence for a home run. Adjustment issues with drop shots too. Remember - follow through, and don't rely overly on wrist action!

Lesson Number Three: The service should be aimed horizontal or upwards, instead of downwards like a badminton smash (the instinctive stroke). This is emphasized in About.com's Tennis Serve Repair guide, and we can resort to basic kinematics to back up that statement.


Cross-section of tennis court, to scale

To make the computations straightforward, assume the service is hit perfectly horizontally (parallel to the ground) and the tennis ball undergoes negligible deceleration from air resistance. According to wikipedia, the distance from baseline to net is approximately 11.9m, and from net to service line 6.4m. The net is 0.91m high at its lowest point in the middle. Let the point of contact between racket and ball during service be 2.85m above ground (1.75m height, 0.6m extra reach, 0.5m from handle to racket face).

A successful serve has to (I) pass over the net, and (II) land in the service box on or before the service line. Hitting the ball harder obviously makes it easier to fulfil condition (I), but harder to fulfil (II), and vice versa for a softer hit. Letting the initial (horizonal) velocity be x m/s, and using d = 0.5at^2, the following equations have to be satisfied:

dI = 0.5(9.8)(11.9/x)^2 ≤ 1.94 = 2.85 - 0.91
dII = 0.5(9.8)(18.3/x)^2 ≥ 2.85

Doing all the nitty-gritty steps and converting gives 68.08km/h ≤ x ≤ 86.22km/h, i.e. for a well executed flat serve hit horizontally by a guy of average height, there isn't really a large window of possible speeds. Aiming slightly upwards would likely allow for more error in both the angle and speed, though of course the serve would then be easier to return.

Do note that there is no maximum speed if one's aim is perfect, as the straight line from point of service to the service line passes over the net - Andy Roddick's record is a shade shy of 250km/h (!) Quite clearly a flat serve at that speed would fall nowhere enough to land inside the service box if hit horizontally, and indeed it seems from trigonometry that there is at most a range of a few degrees that such a serve can leave his racket at and remain legal (though he may be helped by being slightly taller). Conclusion: The harder a flat serve is hit, generally the more accurate it has to be as well.

Dinner

And on Saturday my parents took the family out for a seafood dinner. Can't remember the last time I ate crab other than the on-a-stick versions by Old Chang Kee, delicious nevertheless.

Turned down a football invitation for the first time in a long while on Sunday. Needed to recharge.



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