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Newtons as a Measure of Skill (Read 6419 times)
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Newtons as a Measure of Skill
Jan 18th, 2013 at 1:45pm
 
In my opinion, the fact that everyone has different slings and glands should be taken into account in a different type of achievement under the "Slinging Achievements" category. What I suggest we implement is an achievement based on video proof, a formula to calculate the amount of force applied in each throw in the video, and a requirement that at least two people other than the one who submitted the video check the math and measurements of the person submitting the video.

The formula I have come up with to measure the Newtons applied to any given videotaped throw is attached as an image.
The units for each variable are as follows:
T1 & T2: Seconds (T1 likely values range from 0.5 seconds to 8+ seconds) (T2 likely values range from 0.05 seconds to 0.25 seconds)
θ (Theta): Degrees (likely values range from 10 degrees to 60+ degrees)
M: Kilograms. (You will likely get a value at or under 0.250 kilograms)

Assuming the best possible values from the likely values listed above, the force applied would be equal to about 2260 Newtons
Assuming the worst possible values from the likely values listed above, the force applied would be equal to about 2 Newtons

As you can see from the best-case and worst-case scenarios I proposed, the value of the force of a slinger's throw in Newtons has a very wide range of possibilities, and thus would be something that could be tracked as an achievement easily, given the slingers participating have the proper measuring equipment.
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towelie
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Re: Newtons as a Measure of Skill
Reply #1 - Jan 18th, 2013 at 1:54pm
 
The way one would make a video for submission would be this:
The slinger sets up a video camera or digital camera with a video function on a tripod (you can get a tripod suitable for this task for $15) at a 90 degree angle to the direction of the slinger's throw, and also at least 10 to 20 yards away from the slinger's throwing position, thus being far enough away that it could capture the initial angle of the throw, as well as the time until the gland reaches the maximum altitude of its trajectory.
The slinger also weighs the sling and the gland on a scale in front of the camera before each throw (small scales that measure in grams up to at least 1/4 of a kilogram are easy enough to come by).
The slinger takes the video back to a computer and measures all the variables using video and image editing software. (you can find free ones online. For image editing, use GIMP. It has an angle measurement tool and supports layers.)
The slinger posts the video as well as their formula results in Newtons on the slinging.org forum.

The attached image shows everything one would need in order to measure the Newtons of a slinger's throw, minus the camera of course since I couldn't take a picture of the camera while using it. Grin
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Re: Newtons as a Measure of Skill
Reply #2 - Jan 18th, 2013 at 5:16pm
 
  I think that you are going to achieve high levels in the physicist merit category my friend, but you lost me at T1 & T2! Lol.  
  While I'm not adverse to adding categories at some point in the future for measuring power, I think that for the moment I need to concentrate on the copious amount of categories there already are.  
   Happily, I have a to-do list where I have been keeping track of the things that need fixing or adding and this is definitely going in there!  

   As for the witnesses, I don't think that will be necessary..  Recording video and pics of tasks will be highly encouraged, however, The ranking and merit system will be relying heavily on the honor system.  Dishonest Artists Only Dishonor Themselves...

 Thanks for your input and work on this one!  
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Re: Newtons as a Measure of Skill
Reply #3 - Jan 19th, 2013 at 11:14pm
 
Would that be Fig Newton (American cookie / biscuit)  Cheesy they are rather small   Shocked as a target
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Re: Newtons as a Measure of Skill
Reply #4 - Jan 19th, 2013 at 11:21pm
 
hahahahahahahahahahahahahahahahaha
I LOVE FIG NEWTONS!!!!!!!!!!
Best thing since the Sling:)
Grin Grin Grin Grin Grin
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Re: Newtons as a Measure of Skill
Reply #5 - Jan 20th, 2013 at 12:48pm
 
aren't newtons usually used as a measurement of impact ?


And why are you weighing the sling ? (mine usually weigh less than 10 grams)
The weight of the sling has no bearing on how fast the missile leaves the pouch or the weight of the missile - the only two things you need to calculate the total energy imparted to the missile during the throw.  

To be honest It's not a great way to grade slingers. I could very easily skew the figures just by slinging very heavy rocks. They might not fly very fast or far but due to their weight I would be able to impart a tremendous amount of energy to say a 2 lb rock.

That just boils down to how strong the slinger's joints are.

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Re: Newtons as a Measure of Skill
Reply #6 - Jan 20th, 2013 at 4:59pm
 
Curious Aardvark wrote on Jan 20th, 2013 at 12:48pm:
aren't newtons usually used as a measurement of impact ?


And why are you weighing the sling ? (mine usually weigh less than 10 grams)
The weight of the sling has no bearing on how fast the missile leaves the pouch or the weight of the missile - the only two things you need to calculate the total energy imparted to the missile during the throw.  

To be honest It's not a great way to grade slingers. I could very easily skew the figures just by slinging very heavy rocks. They might not fly very fast or far but due to their weight I would be able to impart a tremendous amount of energy to say a 2 lb rock.

That just boils down to how strong the slinger's joints are.



It's not a bad idea to measure power as an achievement, but I think that C_A I right in that the formulae could be manipulated.  So with this certification would also come ammunition standardization(and that's THE "S"-word around here).  Additionally, I would need to break the category down into Slinger Weight classes.  I mean, I'm pretty sure I could generate more power than Squirrelslinger for example, because he's a much younger guy who's also shorter than me.  I would hazard a guess that I would be stronger and almost certainly weigh more than he does as well.  Eventually, Squirrel may be able to sling me under the table, but at the moment, a power competition would be one sided..
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Re: Newtons as a Measure of Skill
Reply #7 - Jan 21st, 2013 at 9:53am
 
Maybe instead of measuring power by formula you could measure power by a standard target.

Like by slinging through some thickness of plywood or concrete or something along those lines.
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Re: Newtons as a Measure of Skill
Reply #8 - Jan 21st, 2013 at 10:53am
 
After reading all the feedback, I think maybe the formula would best be adjusted to measure the initial velocity of the gland instead of the force applied to the sling and gland. The new formula is attached as an image.

Variables are as follows:
T = Time (in seconds) from launching the gland to the highest point in the gland's trajectory.
θ = Angle of gland's trajectory at the initial launch
V = initial velocity of gland in meters per second.

To convert m/s to MPH, multiply V by 2.237
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Re: Newtons as a Measure of Skill
Reply #9 - Jan 22nd, 2013 at 6:54am
 
towelie wrote on Jan 21st, 2013 at 10:53am:
After reading all the feedback, I think maybe the formula would best be adjusted to measure the initial velocity of the gland instead of the force applied to the sling and gland. The new formula is attached as an image.

Variables are as follows:
T = Time (in seconds) from launching the gland to the highest point in the gland's trajectory.
θ = Angle of gland's trajectory at the initial launch
V = initial velocity of gland in meters per second.

To convert m/s to MPH, multiply V by 2.237


Do some research on this, post your findings and Petition for your Physicist Merit Award!  Easy money my friend (well, for you anyway...  Grin).
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Re: Newtons as a Measure of Skill
Reply #10 - Jan 22nd, 2013 at 8:02am
 
I don't understand the because to a difficult, neither I understand the importance of the weight of the sling in the projectile...

Is more easy, if the cameras record to 30 or 24fps, only be measured the distance traveled for the projectile between two first frames... if is 2 meters at 30fps... 60m/s is the initial speed.

Also, with this method you can obtain many frames and draw a curve speed/time... with sampling of the first 20 meters (with more sampling more accurate) i can know with little error that will happen in the near 150 meters, also know if you want, the air friction coefficient of the your projectile (if you know the atmospheric prassure, the direction and speed of wind), the distance (if you measure the angle.. easy with the video), the newton initial and final, the work...
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Re: Newtons as a Measure of Skill
Reply #11 - Jan 22nd, 2013 at 8:41am
 
Measuring these angles (small typically) and locating the highest point of the trajectory are rather difficult to do well.

With some overhand-style target shooting, with the projectile launched from way above head height, the trajectory will start downwards, and there will not be a highest point to measure.

If you want an estimate of velocity, isn't it easier to check how long it takes to hit the target?

Cudol,

Those of us who have tried have found video analysis is far easier said than done with current 'consumer' equipment, at least to to any decent precision, although the cameras are getting better all the time. By far the best so far is this thread http://slinging.org/forum/YaBB.pl?num=1339861833/12 from about a year ago.

The maker is both an excellent (accurate and fast) slinger, and a professional engineer who set up his system with appropriate care.
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Re: Newtons as a Measure of Skill
Reply #12 - Jan 22nd, 2013 at 10:11am
 
wanderer wrote on Jan 22nd, 2013 at 8:41am:


Really good!!
That's what I had in mind.

I see it easy, many people calculate the speed of trains, planes ... by this method.

Digital video cameras are very accurate because, one small error would produce that one record of 1 hour, produce a longer or shorter film, few seconds more or few seconds less... but that does, not happen because the actual cameras are very accurate.

I think that this method is easy and accurate is good for the initial speed... only need: one camera, one tripod, one object with a measure known situated in the same plane (one cardboard box for example), much light, and one software.
The camera would be situated far, for decreasing the angle error.

You multiply the distance between two frames with the number of frames for second.

For extract more values with one film, you need knowledges of cinematic and dinamic or use "slinging simulator" ( http://slinging.org/forum/YaBB.pl?num=1358332946 )
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Re: Newtons as a Measure of Skill
Reply #13 - Jan 22nd, 2013 at 2:45pm
 
nice - yeah if yureks applied  his mind to it he's probably nailed it Thumbs Up

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Re: Newtons as a Measure of Skill
Reply #14 - Jan 22nd, 2013 at 9:55pm
 
[If a mod wants to kick this discussion out of this section and put it somewhere else, I don't have any problem with that Smiley]
Cudol, you are right that the method works very well for measuring velocities.

The problems really start when you start investigating the other stuff. To find velocities you've subtracted the coordinates of two observed positions of the projectile. Most consumer cameras don't give each of these positions to anything like pixel accuracy since they play games with the chip to run them at video speeds. To get accelerations you need to subtract two uncertain velocities, and the result is that your uncertainties get pretty high if you are interested in how drag (and hence observed acceleration) changes with velocity.

You also have to be very careful with optical distortion on the camera lense, and on parallax.

With the right kind of camera, these things are probably a lot easier now than they were only a year or two ago. Unfortunately anything I have is, I know, not up to the job Smiley.
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