can someone please tell me what the formula is to figure out my kinetic energy please...i'm shooting a 650gr arrow at 61pounds at 190 fps...i keep coming up with 51 pounds.that sounds wrong for that heavy of an arrow doing 190...thanks :banghead:
I thought trad would be simpler...LOL Can you google Kinetic energy it should give you the formula
just curious :bigsmyl: :dunno:
This is what I found.
The kinetic energy of an object of mass m traveling at a speed v is mv2/2, provided v is much less than the speed of light.
you can use this link
http://en.wikipedia.org/wiki/Kinetic_energy#Calculations
Speed times Speed times weight divided by 450,240. This will give you the kinetic energy of the arrow at the distance you measured the speed at. Most shoot at three or four feet away from the chronograph.
I found a kinetic energy calculator for you to look at.
http://www.dewclawarchery.com/Kinetic_Engery_Calculator-a/157.htm
52.1 and .548 momentum
Pretty dang good for a stickbow.
Mike
I'm not sure why you would want to calculate KE. Maybe like me you are a nerd :-) . Either way, the more important calculation when considering how much damage an arrow will do is momentum. Good luck and I hope you find what you are looking for!
i was just curious to know thats all.i knew that gr arrow and speed would be good elk medicine.
thanks wingnut
So Help out a poor dumb country boy, which is better, faster or heavier? I know the pingpong ball and golf ball in the snow deal. I'm asking, when does a faster lighter arrow, out perform a heavier slower arrow? There's got to be a point where lighter is better. Just curious. Don
i think the heavier arrow will always be better unless you're shooting a very slow bow maybe.not sure about that one though,maybe someone will chime in.
It's a balancing act. You always want enough broadhead and arrow to get an exit wound on your animal. For me that is usually about 10-11 gpp and a top end BH.
Going Moose hunting in a month and we are shooting 720 gr arrows with Abowyer Brown Bears. I'm restricted to no more then 50# so my bow is 52 @ 30.5.
Mike
good luck
If you double the weight of your arrow, you lose only one half of your velocity. So in answer to Dons statement that " at some point lighter is better", Lighter will never have more momentum. I think 650gr. arrow going 190fps will shoot thru 2 elk.
yep it sure will.gonna have my hardened snuffers guidin the way.
Mike. . no MORE than 50 # ? Hmmmm well it is probably 50 # at 29" there ya go !
ChuckC
I've have heard from a reputable source, that in order for a 650 gr arrow or above to be the most effective. It has got to be going at least 155fps. Never tried it personally, but I do trust the source.
to calculate kinetic energy... take your arrow speed in fps, squared..
210 fps x 210 = 44,100
divide by 450,240 ( a constant ) 44,100/450,240 = .09794
then multiply .097794 x arrow weight 515 = 50.44 KE
Ashby's formula for momentum is written in TBM April/May 2007. On page 50, he states an arrow must meet or exceed the threshold of 14.8 pd-feet/sec of momentum . He has a chart of arrow weight and the correllating speed in fps to have the necessary momentum.
550gr @ 189 fps, 600gr @ 173 fps, 650gr @ 160 fps. Hope that helps
download the easton shaft selector program 9too stiff in my experience) but it does have a KE calculator
The simple physics formulas are:
Ke = 1/2 (m) ( v^2) where Ke is kinetic energy, m is mass, and v is velocity
P = mv where P is momentum, m is mass, and v is velocity
Of course, if you are looking for units of (lb)(feet)/sec then make sure you use those units in your measurement or convert them accordingly.
Momentum is the more important factor because it reflects loss due to things like sounds and friction more accurately when considering penetration. Friction affects v while mass is unchanged. If v is squared (as in the Ke calculation), then it will show the effect of the loss more than if it is not squared (as in momentum). Both are conserved consistently throughout the flight and impact of the arrow, but momentums are easier to compare. Ke is not because it is nearly impossible to calculate and thus compare the effects of friction and such.
Remember, all of these values are instantaneous. That way we keep the calculus out of it!
Hope that helps!
What kind of bow at what draw length? That is some almost unbelievable speed for 61# bow and 650 grn arrow.
Personally I would be happy with 160 fps with a 650 grn arrow. Should shoot through any elk.
That's a good point Shaun.It just goes to show you how little KE tells you about real terminal performance.Momentum is a much better indicator,all other things being equal.The momentum figure that Wingnut came up with for that setup is pretty high.Most compound setups wouldn't come close to that momentum figure but their KE would sound better.
If I had a bow that would move a 650 gr arrow,190 fps,I wouldn't care what the figure was.I can't imagine a more efficient setup.I'd like to know what bow that is also.I want one.
AS for the question about when is lighter more effective than heavier. There is a point when lighter is more effective and it will be different for each bow. If you doubt that go out in your yard with a golf ball, a baseball and a 16# bowling ball and throw them all overhand at a target 20yds away and see which one is the most effective. I bet the bowling ball won't even get there. I know this is an extreme example but the same principles apply.
There will be a definite bell curve if you sit around and try to figure it up, so there is a definite peak at which the heavier arrows will become less effective. So for instance a 600 gr. arrow may preform the same at certain distances as an 1100 gr. arrow depending on tyour setup.