It's About Time C

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Primate
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Re: It's About Time C

Postby Primate » March 8th, 2010, 5:35 pm

Hey! I'm new to this event, and I'm still a little confused on the test.

How do you recommend my partner and I to do the test- Should we split it in half and work on it separately? If so, how do we share the binder in an effective manner? (we had trouble on this during regionals.)

Also, how long are most people's binders? What method of organization did you find best?

If anyone has done this event more than once- do you often see random trivia based on time in tests? On our regional test, there was a question on the incubation period of H1N1, and we had no idea. If so, how do you suggest to prepare for these sorts of things?

Thanks! :) Any information at all would be great.
What I've found effective is to take all the information and categorize and paginate it. Then, I auto-generate a table of contents, and I'm all set. Thank goodness for Microsoft Word. You could try indexing it, too, but that might be more time-consuming than it's worth. I get all my information to comfortably fit in a 1.5" binder, at least for regionals. I've seen some people with massive binders, though.

Splitting the test in half and working on it separately is a great strategy. My partners and I have usually been able to share the binder pretty easily; if you need it for a question and its in use, just skip to a question you don't need it for until your partner finishes. If it's organized well, you won't need to use it for long. If you're really worried, I guess you could make two copies of everything, staple them into two packets, and then remove them from the binder once competition begins.

And yes, random trivia shows up all the time. In fact, I think we had the same question. As far as I know, the only way to prepare for it is to find all the random bits of time-related knowledge you can.
During competitions, are the time trials generally started using three beeps or one? At Mentor this year it was only one, but all of the other competitions we've been to have been three.
They have to use three. it's part of the rules, isn't it? to use the official SO time trials? they're all available on the official site....
I don't think it's required that you use the official files--you just have to use a computer capable of timing things extremely precisely.

Finally, has anyone managed to get a pendulum with a stiff rod to oscillate for the full five minutes. Even with ball-bearings and a 7lb weight, I can only get it to last for about a minute.
events 2012 gravity vehicle, robot arm, thermodynamics, tps

texan92
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Re: It's About Time C

Postby texan92 » March 8th, 2010, 7:33 pm

Even with ball-bearings and a 7lb weight
7 lbs weight? That's a lot. How heavy is your rod? An ideal pendulum has a massless rod, so the weight of the rod might have something to do with it. Is you base secure? If you structure sways or moves when the pendulum swings, that could dampen your period over time. However, I don't think these factors have enough of an effect to cut the time of your pendulum to one minute.

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Re: It's About Time C

Postby walkingstyx » March 9th, 2010, 3:31 pm

My school uses a stiff rod and we have never had any problem going the full five minutes. You could try dropping it from a greater angle to start with, or using a longer rod. There are lots and lots of factors that go into damping, but generally, if you start off with a larger amplitude, assuming you don't have truly terrible bearings, you should be able to go the whole time.
Nationals 2010- Astronomy: 4, Physics Lab: 4, Picture This: 4, It's About Time: 10, Optics: 2
Nationals 2009- Picture This: 4, It's About Time: 8, Astronomy: 9
Nationals 2008- Picture This: 2, Boomilever: 14

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Re: It's About Time C

Postby texan92 » March 9th, 2010, 5:08 pm

or using a longer rod
I was wondering, if you use a longer rod, wouldn't you have problems with the accuracy of the pendulum? If you increase the rod length, you do gain some accuracy because there is less drag and the pendulum is moving slower. However, how would subdivide your periods? If you have a period of say 1 sec, every half period is 0.5 sec, 1/4 the period is 0.25 sec, etc. With a longer period (say 2 sec), every half period is 1 sec, 1/4 the period is 0.5 sec, etc. With successively longer periods, every subdivision of the pendulum period becomes less and less precise and the human eye has a limit in discerning how precise 1/4 of the pendulum movement is.

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Re: It's About Time C

Postby Primate » March 9th, 2010, 8:02 pm

Yeah, it must be a problem with the bearings. I just reengineered an old trajectory, so whatever junk was used in that got transferred over to this. It's not all that long, I suppose, but I tried dropping it from 90 degrees, just for the heck of it, and it still only lasted about a minute thirty. The rod is a pretty light piece of wood, probably the lightest thing possible for the same stiffness/thickness.
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Re: It's About Time C

Postby rockhound » March 10th, 2010, 7:16 am

or using a longer rod
I was wondering, if you use a longer rod, wouldn't you have problems with the accuracy of the pendulum? If you increase the rod length, you do gain some accuracy because there is less drag and the pendulum is moving slower. However, how would subdivide your periods? If you have a period of say 1 sec, every half period is 0.5 sec, 1/4 the period is 0.25 sec, etc. With a longer period (say 2 sec), every half period is 1 sec, 1/4 the period is 0.5 sec, etc. With successively longer periods, every subdivision of the pendulum period becomes less and less precise and the human eye has a limit in discerning how precise 1/4 of the pendulum movement is.
Be careful with your "etc", the pattern will not continue. Whiile it might not matter, based on the precision of your device, but the halving patters stops at 1/4 of a period.

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Re: It's About Time C

Postby walkingstyx » March 10th, 2010, 2:43 pm

You have a good point, but you make some bad assumptions. 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. You can tell 1/4 periods without any estimation at all, so you are perfect down to .4 seconds. As the size of your pendulum increases, estimation becomes easier, so you can tell it down to .1 seconds pretty easily with a little practice. As long as you practice often, even a 80 cm pendulum can be estimated accurately to 1/10 of a second. Considering that you have to calibrate it and practice for competitions, you should more than enough practice to sight .1 seconds.
Nationals 2010- Astronomy: 4, Physics Lab: 4, Picture This: 4, It's About Time: 10, Optics: 2
Nationals 2009- Picture This: 4, It's About Time: 8, Astronomy: 9
Nationals 2008- Picture This: 2, Boomilever: 14

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Re: It's About Time C

Postby nnayar12 » March 11th, 2010, 7:07 pm

Hi everyone,]
I'm new to this event, and I was wondering specifically what types of questions you have encountered in the written test of It's About Time. I've been reading a bunch of books, but it seems there is just so much to cover on the broad subject of time! Some things I have been looking into are time-related physics, calendar conversions, and history of time-keeping. Any other important things we should cover?

Also, does anyone know of any good ways to find easy calculations to convert between calendars. I'm finding it particularly challenging to convert between solar and lunar calendars because they are just so unrelated and unpredictable, yet they were on the regional exam so apparently I need to know how to do them.

Finally, how advanced does the physics on the exam get? From your own experiences, are there many questions on relativity including things like Minkowski diagrams and Lorentz transformations? And did you need to know them just conceptually or mathematically too?

Any input would be appreciated.
Thanks!!!

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Re: It's About Time C

Postby Bogoradwee » March 12th, 2010, 3:03 pm

Hi everyone,]
I'm new to this event, and I was wondering specifically what types of questions you have encountered in the written test of It's About Time. I've been reading a bunch of books, but it seems there is just so much to cover on the broad subject of time! Some things I have been looking into are time-related physics, calendar conversions, and history of time-keeping. Any other important things we should cover?

Also, does anyone know of any good ways to find easy calculations to convert between calendars. I'm finding it particularly challenging to convert between solar and lunar calendars because they are just so unrelated and unpredictable, yet they were on the regional exam so apparently I need to know how to do them.

Finally, how advanced does the physics on the exam get? From your own experiences, are there many questions on relativity including things like Minkowski diagrams and Lorentz transformations? And did you need to know them just conceptually or mathematically too?

Any input would be appreciated.
Thanks!!!
look at the official It's About Time page on Soinc.org. that site's there for a reason. use it. they have really awesome links.
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2009: I don't remember/ not very noteworthy.
2010: See above.
2011: Regionals- 3rd WIDI, 3rd Optics, 3rd Fossils, 3rd overall States- 4th WIDI

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Re: It's About Time C

Postby Arabesque » March 14th, 2010, 9:45 am

Just as an update, the same guy who ran Time at the Mentor invitational, also ran it at our regional yesterday and he switched from one beep to start and one to end to three beeps to start and three beeps to signal the end. Is that typical?

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Re: It's About Time C

Postby walkingstyx » March 14th, 2010, 8:10 pm

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?
Nationals 2010- Astronomy: 4, Physics Lab: 4, Picture This: 4, It's About Time: 10, Optics: 2
Nationals 2009- Picture This: 4, It's About Time: 8, Astronomy: 9
Nationals 2008- Picture This: 2, Boomilever: 14

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Re: It's About Time C

Postby Fuzzy Mint » March 15th, 2010, 5:19 pm

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....

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Re: It's About Time C

Postby Chikuwa » March 15th, 2010, 5:25 pm

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

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Re: It's About Time C

Postby harryk » March 17th, 2010, 12:52 pm

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
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walkingstyx
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Re: It's About Time C

Postby walkingstyx » March 18th, 2010, 1:17 am

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.
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.
Nationals 2010- Astronomy: 4, Physics Lab: 4, Picture This: 4, It's About Time: 10, Optics: 2
Nationals 2009- Picture This: 4, It's About Time: 8, Astronomy: 9
Nationals 2008- Picture This: 2, Boomilever: 14


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