Author Topic: Recording High-Tosses  (Read 6564 times)

Aaron Z

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Recording High-Tosses
« on: September 24, 2008, 07:13:01 am »
Alright, I had a quick think about high-tosses when looking at the Diabolo Records thread. Obviously, high-tossing would be a pretty fun record to go about setting, but people had been having a hard time thinking of a way to record diabolo height.

Well, I think I have a rough answer.

Unfortunately it does require a bearing-diabolo, a Fly would be best for it's wide axle.
A very long spool of string is tied at one end to the Fly's axle, which shouldn't roll-up the string in bearing mode.

The spool is then held on the ground in a way that it can easily unwind when pulled on. Simply get the Fly spinning and pelt it skyward. When it comes back down, measure the length of string it pulled up with it.

I mean cheap twine or thread, by the way, not diabolo string.

William

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Re: Recording High-Tosses
« Reply #1 on: September 24, 2008, 08:02:00 am »
1) You are so lame :P
2) Wouldn't the string create more drag?
William - YouTube! "NO! If they're blue, you should not touch your nuts." - Aaro

Aaron Z

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Re: Recording High-Tosses
« Reply #2 on: September 24, 2008, 09:10:39 am »
1) Home from school, bored, could be fun at MJC.
2) Depends how you go about it.

William

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Re: Recording High-Tosses
« Reply #3 on: September 24, 2008, 12:04:12 pm »
could be fun at MJC.
Bring the string and I'll bring all the fun you can imagine.
William - YouTube! "NO! If they're blue, you should not touch your nuts." - Aaro

Martijn

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Re: Recording High-Tosses
« Reply #4 on: September 24, 2008, 12:26:27 pm »
That's pretty ingenious.
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Toby

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Re: Recording High-Tosses
« Reply #5 on: September 24, 2008, 02:49:45 pm »
I dont think that would be a very fair way of judging it. The string would definately impeed the diabolo!

If I were to try and meassure it, I'd start a timer at the peak of its height, then stop the timer when it returns to the ground/person. Using simple pysics/maths (suvat and all that malarkie) you can calculate pretty accurately how far up it must have been. The only problem being that it would be difficult to accurately start the timer at the diabolos peak, but not too hard. You could always work on averages.

Marijn

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Re: Recording High-Tosses
« Reply #6 on: September 24, 2008, 03:33:35 pm »
You could use a camera to record to throw and then watch in slow-mo when it is at it's peak and when it's back on the ground etc. Ideally you should try it in a hangar or something like that for more accurate measurements (and therefore more accurate calculations).
''I have been practising some basic 2d suicide stuff to widen my arse''

Sean

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Re: Recording High-Tosses
« Reply #7 on: September 24, 2008, 03:44:37 pm »
Neat idea, but I think the growing weight of the string would throw it off. Would make an interesting physics problem. You'd have to calculate the jerk.

A stopwatch and a little knowledge of the rate of acceleration caused by gravity is all that's needed for an approximate answer of a normal throw (ignoring air friction). I think we discussed this somewhere, no?

Ben.

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Re: Recording High-Tosses
« Reply #8 on: September 24, 2008, 04:05:09 pm »
WHY

Marijn

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Re: Recording High-Tosses
« Reply #9 on: September 24, 2008, 04:42:52 pm »
''I have been practising some basic 2d suicide stuff to widen my arse''

ecuador16

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Re: Recording High-Tosses
« Reply #10 on: September 24, 2008, 06:40:15 pm »
why make it hard?
just go to a building where the floors are clearly visible
measure one of them then toss your diabolo watch the footy and you can get a pretty close estimate

i know its not perfect but much easier than other ideas

Toby

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Re: Recording High-Tosses
« Reply #11 on: September 24, 2008, 07:09:06 pm »
I disagree, whats difficult about using a stopwatch?

You dont need a ladder either, which i guess you would need to get an accurate meassurement of the height of one floor. You'd have each to find a building the fitted the bill too, whereas you can time something anywhere.

Sean

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Re: Recording High-Tosses
« Reply #12 on: September 24, 2008, 07:51:57 pm »
If you work out the math it's
 
maximum height in meters = 9.81/8*t^2

where t is the time from throwing to catching measured in seconds.

in words: "9.81 divided by 8 times the number of seconds squared"

or more simply, approximately: 1.2*t^2

For ease of calculation at the time you could think of it as slightly larger than the time squared.

If you recorded the right time, used the precise rate of acceleration due to gravity (9.80665 m/s^2), and did this in a vacuum (i.e. no air resistance), you'd get the exact height.

Martijn

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Re: Recording High-Tosses
« Reply #13 on: September 24, 2008, 08:12:16 pm »
Combine that with an accurate method of determining the time (i.e. filming it) and you'll have a great way of showing off :P

You'll need to film it anyways to be verified :)
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-Leo-

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Re: Recording High-Tosses
« Reply #14 on: September 24, 2008, 08:21:12 pm »
Actually there are a few problems with the string idea, although it was a nice thought. When the diabolo reaches its maximum height and starts to fall the momentum the spool has from being spun already will keep it spinning and so unwind more string. Also the throw will cause a jerk in the string. The effect of a jerk can be solved with relatively simple mechanics, but it is overcomplicating the measurement of the throw completely.
 

EDIT: I forgot to read the second page of this thread, but Sean's method is far superior. You can add in some air resistance to that calculation if you want to be super-accurate though :P
Behind your back is your front.

Marijn

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Re: Recording High-Tosses
« Reply #15 on: September 24, 2008, 08:59:11 pm »
If you work out the math it's
 
maximum height in meters = 9.81/8*t^2

where t is the time from throwing to catching measured in seconds.

in words: "9.81 divided by 8 times the number of seconds squared"

or more simply, approximately: 1.2*t^2

For ease of calculation at the time you could think of it as slightly larger than the time squared.

If you recorded the right time, used the precise rate of acceleration due to gravity (9.80665 m/s^2), and did this in a vacuum (i.e. no air resistance), you'd get the exact height.

I'm probably missing the point :P :P, but why can't you just use
.5 * 9.81 * t^2 =  distance travelled (from the 'top' of the throw to the ground) considering it as a regular free fall with start-velocity = 0
''I have been practising some basic 2d suicide stuff to widen my arse''

Sean

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Re: Recording High-Tosses
« Reply #16 on: September 24, 2008, 11:03:57 pm »
...but why can't you just use
.5 * 9.81 * t^2 =  distance travelled (from the 'top' of the throw to the ground)
That's exactly what I did. Remember, distance travelled from the top to the ground is only 1/2 of the time recorded, so:

d = 1/2 * 9.81 * (1/2t)^2
d = 1/2 * 9.81 * 1/4 * t^2
d = 1/8 * 9.81 * t^2
d = 9.81/8 * t^2

Marijn

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Re: Recording High-Tosses
« Reply #17 on: September 24, 2008, 11:07:51 pm »
That's exactly what I did. Remember, distance travelled from the top to the ground is only 1/2 of the time recorded, so:

d = 1/2 * 9.81 * (1/2t)^2
d = 1/2 * 9.81 * 1/4 * t^2
d = 1/8 * 9.81 * t^2
d = 9.81/8 * t^2
Aha, I assumed one would start recording/start timing when the diabolo is at his top ::) I usually get lost in English math/physics words since it isn't my first language and it aren't ''every day'' words. Thanks for clearing it up.
''I have been practising some basic 2d suicide stuff to widen my arse''

Sean

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Re: Recording High-Tosses
« Reply #18 on: September 25, 2008, 12:05:42 am »
Well, your English sure beats my Dutch!

You try figuring out when the diabolo is exactly at the top while looking up from below. ;)

Aaron Z

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Re: Recording High-Tosses
« Reply #19 on: September 25, 2008, 07:52:35 am »
If the spool of string had already been un-wound as was lying neatly on the ground, the Jerk factor would be greatly lessened.

Of course, if everyone just used the exact same outlined method, then it should be fair game with everyone experiencing the same amount of resistance from the string.

Timing does seem like the way to go, probably also the most hassle-free. Granted that there is a reliable formula to be used.

I'll test and record the string idea at the MJC on Saturday.