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I've never heard of anything like that. It has been three to start and one to end at every competition I've gone to this year. Nationals will use the sound files posted on the official website, with three to start and one to end.

In an unrelated topic, I was reading recently about the cool properties of cycloids, and one of them is that you can use them to make pendulums that oscillate with the same period despite different amplitudes. Does anyone know how to get a pendulum to oscillate through a cycloid rather than the semicircles you would normally get? Also, has anyone done anything like this and had any success?

Hi!
okay, so, I'm totally new to this event, so does anybody have any helpful links or hints for somebody who has pretty much no idea how to do this? because pretty much all I know right now is that it has to do with time, and you can use a pendulum or some sort of time keeping device....and what do these sound files or beeps have to do with time?
Thanks!
sorry, this has probably been brought up before, but I really have no idea how to start....

Fuzzy Mint wrote:Hi!
okay, so, I'm totally new to this event, so does anybody have any helpful links or hints for somebody who has pretty much no idea how to do this? because pretty much all I know right now is that it has to do with time, and you can use a pendulum or some sort of time keeping device....and what do these sound files or beeps have to do with time?
Thanks!
sorry, this has probably been brought up before, but I really have no idea how to start....

Well, first you might want to read the rules for the event. That would probably clear up some of the confusion. If your coach hasn't already given them to you, you should ask for them.
You can also look at the SciOly wiki entry here: http://scioly.org/wiki/It%27s_About_Time

walkingstyx wrote: The longest period you can have anyway is only 1.8 seconds, due to the size limit on the clock. Theoretically you could expand it after the event started, but I don't see why you would do this with a pendulum.

well I made mine with a 2 sec period and a 1 meter length. I used a bicycle cable and hung an approx 200g weight.
There are three problems with using a rod:
1- friction at the hinge point, even with alot of lube it will still get friction
2- rods can be heavy, defeating the point of a massless rod
3- since its moving in a 2d plane it cannot rotate like a normal pendulum will, creating more friction

when your building a stand to hang your pendulum from, make it as sturdy as possible (that means no kinex, pvc pipe, balsa wood, rulers)
if your stand can bend, wiggle, or move with a little force it WILL hurt your accuracy
mine is made out of 2x4's that I bolt together and I use wedges to stabilize it
with this simple build its accuracy is down to less than .1 sec's and after 5 mins it only loses .3 secs
now I'm just dealing with human error, I wish we could be allowed to use push counters I don't see why it would be bad

Also for the test I find it rather annoying how they just stick random facts in there, my school's physics AP teacher has proctered for every competion we've been to and I remember at Greenhill Invit one of the questions was "how long it took concord to fly across the atlantic?" (and yes he did spell concorde wrong)


@ walkingstyx I'll be seeing you at State, and hopefully again at nationals

harryk wrote: well I made mine with a 2 sec period and a 1 meter length. I used a bicycle cable and hung an approx 200g weight.
There are three problems with using a rod:
1- friction at the hinge point, even with alot of lube it will still get friction
2- rods can be heavy, defeating the point of a massless rod
3- since its moving in a 2d plane it cannot rotate like a normal pendulum will, creating more friction

Good points, though I wouldn't worry too much about the last one, as the rotation is more a product of air friction than an inherent property of a pendulum, and the forces causing it are not enough to matter unless you have a very weak frame, and then you have much greater problems anyway. Personally, my team has never found any of these to be an issue, we just calibrate our pendulum to death and don't worry about whether the period is being damped or it is oscillating theoretically perfectly. The reason I generally talk about rigid pendulums in this forum is because I know them pretty well, so I can troubleshoot them more easily, not because they are inherently better.
That being said, I don't think your pendulum is legal. 1m is generally longer than 80cm, so unless you can fit it into the cube in pieces and assemble it after competition starts, and it doesn't sound like it from your description, you are violating construction parameter e.

harryk wrote: now I'm just dealing with human error, I wish we could be allowed to use push counters I don't see why it would be bad

I think they are discouraging push counters in an effort to make us build clocks that can count for us with escapements, to make the event more complex.

Also, the questions on those tests were no more ridiculous than the dogwatch and nstc television questions on nationals last year. I rather liked them, and they were similar to what you should expect on the Texas state test, though they had a greater emphasis on math than the nationals test probably will.

walkingstyx wrote: I don't think your pendulum is legal. 1m is generally longer than 80cm, so unless you can fit it into the cube in pieces and assemble it after competition starts, and it doesn't sound like it from your description, you are violating construction parameter e.

That is exactly what I did , I have to bolt it together in the 5min calibration period given in the rules

what sort of questions did people typicaly get on the writing portion?

Fuzzy Mint wrote:what sort of questions did people typicaly get on the writing portion?

Ohh... you dont want to get me started
take a look through this thread, especially page 8
It will probably let you know what you're in for

I think it's funny how a lot of people posted stuff like, "i'm new in this event... give me answers..." kinda stuff when theres already someone who asked that...
Well, in my regional competition the written test was impossible! It talked about Newton and how time is continuous, then gave us 3 super difficult problems that had nothing to do with what i studied(UTC, time zones, pendulums, etc.). It was about dx/dt and stuff which I'm pretty sure is Calculus but w/e we got 15th(which is pretty bad)... hopefully the written test is more decent in the State competition....

SuzumiyaTsuna wrote:I think it's funny how a lot of people posted stuff like, "i'm new in this event... give me answers..." kinda stuff when theres already someone who asked that...
Well, in my regional competition the written test was impossible! It talked about Newton and how time is continuous, then gave us 3 super difficult problems that had nothing to do with what i studied(UTC, time zones, pendulums, etc.). It was about dx/dt and stuff which I'm pretty sure is Calculus but w/e we got 15th(which is pretty bad)... hopefully the written test is more decent in the State competition....

Yeah, regional event coordinators often fail to realize just how impossible it is to study for the entire topic of time. Ironically, the most fair It's About Time test I've taken was the one at the New York state competition. I think there were just over 25 questions, with about a quarter being computational and the rest being facts. For example, we were asked to find out the number of seconds in a week, how long it would take an astronaut to travel 4.3 lightyears if he were traveling at 90% the speed of light, the length of the Ordovician period, and the number of yottaseconds in a yoctasecond.