I've seen u tube videos of slingers hitting targets from various distances. They ranged anywhere
from 10 to 50 feet. Got me wondering. Is this a fair test of the power? I mean, is the power of the stone the same at 10 feet, than say 50 or 100?

The power of any projectile will fall off the further it goes.  This is due to a loss in velocity.  The energy, or power, of a projectile can be calculated by multiplying the weight times the velocity squared, and then dividing by 450395 (this is if the weight is in grains, and the velocity is in feet per second).  Given the greater mass of a sling projectile over a rifle or pistol bullet, velocity is not lost as rapidly, and overall energy remains more constant at greater range.  
That being said, you are definately going to have a difference in hitting power between 10 and 100 feet.  How much depends on how fast you can sling, and how heavy you projectile is.

Here are a pair of handy wesites when trying to calculate the foot pounds of energy from a projectile.  The first is the energy calculator, and the second allows you to convert whatever weight measurment you use on you sling stone into grains for entering into the balistic calculator.
http://www.reloadammo.com/footpound2.htm
http://www.saveonscales.com/weight_converter.html

Silly conversions, go metric.... ;)

hehe, granted, but since I'm familiar with the balistic information from firearms, that's how I go about doing things.  Cumbersome I know, but it's what I'm used to  :)

This forum is not a political forum.Nobody really cares what unit of measurement is used,Let's spend our time reading and posting important information, and quit with the pissing contest.

 PLEASE.

aw, man....I was wondering if someone could get up enough Poundals to lob an 80 dram ball of 4 nails circumference more than 100 Ells!

just wait untill you are as ols as I am some of us are still using Cubits

Quote:

This forum is not a political forum.Nobody really cares what unit of measurement is used,Let's spend our time reading and posting important information, and quit with the pissing contest.  PLEASE.

Someone have a bad day ?
What's politics got to do with it. I've just written up a recipe and realised at the end that I've used millitres, grams and ounces. lol
And i'm not going to change it either lol

As for the power at different distances - well I throw harder at targets that are further away.
So I suppose it depends on whether you are  intent on just hitting a target - in which case you tend to throw as hard as needed and no harder. Given that the harder you throw the less accurate we tend to be.
Or whether you are intent on doing as much damage to a target as possible in which case you throw as hard as you can at all distances.

In the first instance (just target shooting) targets further away will be hit with more power than targets close up. In the second instance it would be the reverse.
:-)

Burner wrote on May 16^th, 2008 at 12:20am:

This forum is not a political forum.Nobody really cares what unit of measurement is used,Let's spend our time reading and posting important information, and quit with the pissing contest.  PLEASE.

My, my, we ARE a bit touchy aren´t we?
 Grown up in the Netherlands, in that enlightened part of the world that knows reason, has shed the barbaric traditions of the dark ages and therefore abides by the superior metric system, I´ve never seen these conversions before, and they are funny (and cumbersome indeed).

there is also the question though of gravity helping out with longer casts...

with guns, it is more or less straightforward.  the bullets travel in an almost straight line.  sling bullets over longer distances are travelling in arcs, so gravity adds to the accelleration as they start coming down...no?

so could you say that longer distance shots hit harder than short distance shots perhaps?  or is it more or less balanced out?

Siguy,

 Absolutely not.The projectile has maximum velocity upon release and slows down from there.At the peak of the arc the object has already been overcome by air drag,and gravity cannot help it.If you were throwing off of a cliff or mountain things might be different,I think.Then the object would find its terminal velocity.

Thomas,any input on this question from Siguy?

siguy wrote on May 17^th, 2008 at 11:39pm:

there is also the question though of gravity helping out with longer casts... with guns, it is more or less straightforward.  the bullets travel in an almost straight line.  sling bullets over longer distances are travelling in arcs, so gravity adds to the accelleration as they start coming down...no? so could you say that longer distance shots hit harder than short distance shots perhaps?  or is it more or less balanced out?

It's just the same as tossing a ball straight up into the air. It has maximum speed at the instant it leaves your hand. On the way up both air resistance and gravity slow it down until it stops and starts to come down again. Now gravity makes it accelerate but air drag still tries to slow it down so when you catch it the speed is slower than it was when it left your hand on the way up. If there was no air then the ball would actually regain all its speed and hit your hand with the same speed as it was thrown with. Of course this cannot happen in reality because even in high mountains there is always some air drag. Heavy, dense projectiles are less affected by air drag. That's why baseballs can be thrown a long way whereas tennis balls which are about the same size but much lighter don't go nearly as far. Also air drag varies as the square of the velocity ie. double the speed and air drag goes up 4 times. So a slower moving heavy projectile will retain a greater percentage of its original kinetic energy and "hit harder".

There is no terminal velocity if something is being acted upon by an outside force.

Somewhere I read about baseballs terminal velocity at 97 mph. A typical golf ball driven out to 250 yards will land at around 45 mph.

tom

bigkahuna wrote on May 18^th, 2008 at 7:15am:

There is no terminal velocity if something is being acted upon by an outside force.

This "terminal velocity" notion can be a little confusing. It doesn't mean that an object cannot be thrown faster than this speed, only that a freefalling object will not go faster. Of course an object moving horizontally at this speed will be subjected to an instantaneous retardation of 1 g, ie. losing speed pretty quickly.

Exactly, terminal velocity is just that. I don’t know what the golf ball terminal velocity is.

tom

If you throw an object off a cliff,at a respectable angle(30-40 degrees),it will increase speed after it descends below the horizontal plane of takeoff.Is that not correct,assuming that the object will have sufficient enough time to fall  far enough to reach its terminal velocity?

Burner wrote on May 18^th, 2008 at 9:47pm:

If you throw an object off a cliff,at a respectable angle(30-40 degrees),it will increase speed after it descends below the horizontal plane of takeoff.Is that not correct,assuming that the object will have sufficient enough time to fall up far enough to reach its terminal velocity?

The scenario you propose complicates things and there is no single yes or no answer. IN THEORY if there was no atmosphere the object would be losing speed until it reached the top of its trajectory. Once it started coming down again it would regain speed and be travelling at the same speed which it was originally thrown once it reached its original level. It would then continue accelerating until it hit the bottom of the cliff. With no atmosphere there is no such thing as terminal velocity. Of course atmosphere is always present and air drag is always directly opposing motion.

The best analogy I can think of is it's like riding a bike with the brake dragging. You can still ride it and it will even roll uphill a bit if your speed is high enough. But even downhill it won't go as fast as if the brake was off. It always opposes motion whichever way you're going. And there is going to be a speed beyond which you will not be able to go no matter how hard you pedal.

Whether or not your thrown object reaches terminal velocity depends on what it is, how hard you threw it and how high the cliff is etc. Also your projectile has a horizontal component to its velocity, ie. it's moving over the ground not only going straight up or down under the influence of gravity. Assuming your projectile is a baseball, it will reach terminal velocity if the vertical component of its velocity reaches the 97 mph quoted above. Because it also has a horizontal componenet to its velocity which is not affected by gravity its actual speed through the air may in fact be slightly higher.

However the horizontal componenet is also constantly being reduced by air drag. That's why a high arcing shot always hits the ground with a steeper angle than the one with which it as thrown. The ball's speed over the ground is constantly reducing so eventually it will be falling almost vertically.

Hope that helps.

bigkahuna wrote on May 18^th, 2008 at 7:15am:

There is no terminal velocity if something is being acted upon by an outside force.

At the terminal velocity the gravitational force on the body is balanced exactly by the drag force, so the total force on the body is zero, and so it's velocity doesn't change.

The terminal velocity is a really helpful figure when we think about sling bullets. If we can sling at a speed say above half the terminal velocity, then we need to worry about loss of speed due to air resistance. Unfortunately although one can compute these things (there is a little bit on drag in the WIKI) the figures are unreliable because the fudge factors (drag coefficients) are very sensitive to circumstances.

A few figures I get are:

baseball ball	35.1m/s	78.9 mph	86.9m
cricket ball	37.0m/s	83.3 mph	96.8m
tennis ball	24.4m/s	55.0 mph	42.2m
golf ball	33.4m/s	75.2 mph	78.9m
50gm lead ball	73.0m/s	164.3 mph	376.9m
#2 birdshot	31.6m/s	71.0 mph	70.4m

The last column is the distance in metres that the projectile will travel to lose half it's speed just through air resistance. The last line on birdshot is there because I could find some ballistics information on shotgun pellets. The figures for this match very well with published figures.

It's clear that we are all affected pretty strongly by air resistance when we sling, except perhaps with lead glandes.

The figures assume all the projectiles are smooth spheres (drag coefficient 0.47 - OK I know that's debateable!) and are for sea level. I could well believe Thomas' value for terminal velocity of a baseball is correct even though the calculations above predict a lower value. If anyone is interested how these figures are gotten, PM me and I'll see what I can do.

Sorry about the units - but I'm darned if I'm going to work everything in feet per second, etc. >:(

To go back to Slingbadger's original question - the distances give you an idea of how fast these things fall off - clearly air resistance matters ;). Also, if one does the calculations for ellipsoidal shot of the same weights, the bullets travel nearly three times further before they lose half their speed - that's a big improvement for the likes of neolithic hunters with clay shot.