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General >> General Slinging Discussion >> mass, energy, momentum?
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Message started by KnollSlinger on Aug 21st, 2020 at 10:27am

Title: mass, energy, momentum?
Post by KnollSlinger on Aug 21st, 2020 at 10:27am
Those that remember me, thank you.  Where I learned to sling is now all built up.  I could not sling there without smashing windows.  I t is getting harder to get out there and practice.

I weighed the ideal rock that I used to use.  It is four ounces.
It carries 1/4 mile.  Anyone can calculate the energy and momentum?

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Aug 21st, 2020 at 11:55am
Considering air resistance of the type of quartz I throw, I think 300 feet per second is about right.  A one ounce load of shot at 1200 ft per second compares to my four ounces of rock at 300 ft per second.  No wonder the rabbit was a head and the hind legs, with nothing of the middle left over.

Title: Re: mass, energy, momentum?
Post by Sarosh on Aug 21st, 2020 at 12:15pm
wrong Category to post this maybe someone can move it.

1/4 miles ~400m
vacuum minimum velocity = 62m/s
my guesstimation of real velocity in air = 76m/s

4oz=113.398g
energy 332 Joules
momentum 8.6 kg*m/s

details about sling and stone?(length mass shapes design) and or pictures?

Title: Re: mass, energy, momentum?
Post by Kick on Aug 21st, 2020 at 12:16pm
I fear you might have posted to the wrong board...

Title: Re: mass, energy, momentum?
Post by Sarosh on Aug 21st, 2020 at 12:20pm
also how did you spotted where it landed?

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Aug 21st, 2020 at 11:00pm
It sailed over a road 1/4 mile away and kicked up a dust cloud in a field on the other side.  That was a typical throw.  Some when alot further for unkown reasons. Stone was quartz ovoids, 4 oz.  sling doubled up 6'. full spin method like hammer throw.

Title: Re: mass, energy, momentum?
Post by Sarosh on Aug 22nd, 2020 at 5:43am

KnollSlinger wrote on Aug 21st, 2020 at 11:00pm:
full spin method like hammer throw.

I guess you mean pirouette style like timpa because hammer throw is a two arms throw

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Aug 22nd, 2020 at 4:32pm
I introduced the spin method to this group circa 2005.  One hand yes,but the other hand is used for balance.

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Sep 4th, 2020 at 6:24pm
Ok, let's take a look at .45 ACP from a 1911:

Bullet: 0.525714 ounces
velocity: 850 feet per second
momentum: in foot pounds: 27.93

Sling
Bullet: 4 ounces
Velocity: 249.344 feet per second
momentum: in foot pounds: 62.34

ratio sling over 45 automatic: 62.34/27.93 = 2.23

roughly twice. Advantage sling.

energy in units of feet & ounces:
.45 ACP: 189,914.1825
sling     : 124,344.8607

So you see, for stopping power and dramatic flesh removal,
the sling wins.

Title: Re: mass, energy, momentum?
Post by joe_meadmaker on Sep 5th, 2020 at 1:05am

KnollSlinger wrote on Sep 4th, 2020 at 6:24pm:
Sling
Bullet: 4 ounces
Velocity: 249.344 feet per second
momentum: in foot pounds: 62.34

Is a pirouette style being used to achieve this speed?

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Sep 5th, 2020 at 5:26am
It is a style that looks like a discus or hammer thrower.  I used
to throw the discus, pitch baseball, and do shot-put.  Sling for me was always about spinning my entire body and using a "long sling" the knots at eye level, the pocket just touches the ground.  This was my main recreation in high-school and college as I lived on 20 acres with nothing next to that even.

Title: Re: mass, energy, momentum?
Post by joe_meadmaker on Sep 5th, 2020 at 10:13am
That's cool.  I only joined the forum a couple years ago (give or take), and that style has usually been referred to as 'pirouette'.  But I think 'discus' is more descriptive of what is actually being done.  Good description.

Title: Re: mass, energy, momentum?
Post by NooneOfConsequence on Sep 5th, 2020 at 10:39am
If youre judging purely on energy or momentum... the olympic hammer throw is on par with a .308 hunting rifle.

If I had to defend my life though... I think Id prefer a .45 to a sling.

Title: Re: mass, energy, momentum?
Post by Albion Slinger on Sep 6th, 2020 at 6:36pm
I would be interested to see how much kinetic energy could be generated with a projectile twice the weight.
Either way, I find it a bit funny how efficiency drops of with longer slings. It's certainly not a linear increase in power from short ones.

Title: Re: mass, energy, momentum?
Post by woodssj on Sep 8th, 2020 at 6:44pm

An american football has a drag coefficient of about .2, and a 4 oz projectile weighs 1750 grains. I plugged these factors into a ballistic calculator with a 500 f/s initial velocity (the calculator's minimum) and it spat out the attached. Note the 1044 inch drop at 400 yards, equivalent to about 87 feet.

https://www.vcalc.com/wiki/vCalc/Ballistic+Range This calculator gives an absolute maximum of 589 meters of flight with 45 degrees and 249 f/s without drag or other effects, which would be considerable with any projectile, especially with a diameter of about an inch and football shape's coefficient of drag.

I don't think these numbers calculated here are quite reasonable, as a .45 ACP is also listed in the tables as having about 350 ft-lbs of muzzle energy. That's a pretty good amount for a handgun.

Part of the issue is we need a very specific range, not measured in miles, to get this down properly, along with the ballistic coefficient, and a bunch of other data. As the longest recorded shots are all bracketing this range of 400-500 meters, with specialized projectiles having extremely good ballistics, I think there needs to be some more exact measurement before we ascribe velocities and "muzzle" energy to anything.

Someday I'll not be in grad school anymore, and have time to build an online slinging ballistics calculator...

https://en.wikipedia.org/wiki/Ballistic_coefficient

https://web.archive.org/web/20120920043403/http://slinging.org/index.php?page=sling-ranges

http://baseball.physics.illinois.edu/clanet/ClanetSportsBallistics.pdf

https://doi.org/10.1016/j.proeng.2012.04.018 Drag of american footballs.

https://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi Ballistic Calculator

https://en.wikipedia.org/wiki/.45_ACP
https://slinging.org/forum/YaBB.pl?action=downloadfile;file=JBM_-_Calculations_-_Trajectory__Simplified_.pdf (21 KB | 13 )

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Sep 24th, 2020 at 5:42pm
Yes, that would be great.  Or a machine that can track the entire flight of the sling bullet.  Pro baseball has such a machine.  I know, I interviewed with the company in Scottsdale, AZ.  All the teams use it.

I gave my sling the rabbit test.  Head and hind legs remain, minus any connection, and well separated.  That is enough power for hunting.

Title: Re: mass, energy, momentum?
Post by KnollSlinger on Sep 24th, 2020 at 6:51pm
In your link to the table, those ranges appear small, considering my record golf drive on a golf course is 360 yards, and I throw sling much farther than I hit golf balls.

Title: Re: mass, energy, momentum?
Post by woodssj on Sep 25th, 2020 at 8:06pm
So, what exactly is the "Rabbit Test?" knowing a bit more about it might be helpful.

Also, I don't doubt there's enough power in a sling for hunting, I just doubt it's the same as a .45ACP.

I wish the machines didn't cost so much, because they would be a great tool for studying the sling. If I can afford it in future, I'm going to try to get a radar chronograph and see what I can do with it to get some good data.

Title: Re: mass, energy, momentum?
Post by IronGoober on Sep 25th, 2020 at 11:16pm

woodssj wrote on Sep 25th, 2020 at 8:06pm:
So, what exactly is the "Rabbit Test?" knowing a bit more about it might be helpful.

Also, I don't doubt there's enough power in a sling for hunting, I just doubt it's the same as a .45ACP.

I wish the machines didn't cost so much, because they would be a great tool for studying the sling. If I can afford it in future, I'm going to try to get a radar chronograph and see what I can do with it to get some good data.


The referred to "Rabbit test" was hitting a rabbit with a stone from a sling. Apparently it was done with a very long sling and a variatio n of the piroutte technique.

https://www.youtube.com/watch?v=5c6mf8-RqOI
Best radar chronograph for the money. Timpa said he's used one to measure the speed of an air rifle. I've used it for small stones from a sling with no issues. I think the cheaper version (no smart phone connection) is roughly $300. There are cheaper ones (e.g. Bushnell), but I've seen poor reviews from them.

Title: Re: mass, energy, momentum?
Post by woodssj on Sep 26th, 2020 at 10:23am
That's quite reasonable for a chronograph, honestly. I'll have to add it to my list for next year.

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