OK after re-reading you were infact referring to acceleration but the same argument is valid regardless of whether you were referring to acceleration or not. You still can't assume that a bow that is 40 lb pull will launch an object at X speed because there are other variables involved. Also, either way it's still a function of the amount of energy that the bow produces because you are making reference to speed and we know what the weight is so what does that give us when we plug in the numbers? Yep, you guessed it. So either way inorder for the two different bows to launch an object of identical weight at an identical speed then they would have to be producing identical amounts of energy, wouldn't they? Either way your blanket calculation isn't valid.

Sylvan
Ty very much the 8 oz thing helps a ton way eazer for me to put in turmes now.

How do you figger out momentum I would like to know how much my bow has?Is there a web sight to get the momenum chart?




Allso to they 2 people that PMed me I am not full of crap :} [maby but not this time] I shoot a mathews safari set at 90# 29 in draw with a 2514 and a 125 gr point.

You really don't need a chart to figure out momentum.

momentum = velocity times arrow weight divided by 225120

The answer is in pound seconds

for your bow it would be 297 x 552 / 225120 = 0.73 pound-seconds

TY have a good day :}

I'd suggest you do some investigating before making accusations because you have it all wrong. Like I said before (and you may want to re-read), what I quoted was directly from a post on TradGang.com by Dr. Ashby late March 2005. I specifically stated that it was not from his paper. If you'd like to a link to the forum before commenting on it again, PM me and read it for yourself. For someone who claims to be as educated as you state you are, I wouldn't think it would be too hard to comprehend from my previous posts.

BTW FWIW, When claiming to be correct over a known expert in the field who devoted large portions of life through extensive testing in the area, and making statements that his opinions are wrong or "idiotic" to me means that you must believe that you are more knowledgeable.

wow! glad i took calc based physics. sylvan is correct when he says you can learn all this in an entry level calculus based physics course (provided you've taken calc 1 and 2). you guys are arguing with someone based on something someone else explained in laymans terms, with someone who knows the math, the equations, where they are from, and what they do. sylvan isn't inventing anything and has tried to explain things and has given you the equations.

this is like when that person was saying his arrow would go a horizontal distance of 20 yds faster when shot out of a treestand than when shot off the ground, assuming gravity would accelerate his arrow in a horizontal plane, which is impossible.

maybe i've missed the point entirely of dr. ashby's paper. i have read it several times and i agree with sylvan in that i thought dr. ashby's paper was making the point that ke played a small role, but was emphasizing the broadhead's design was more critical in penetration...have i missed the boat? []

by the way, i agree with gibblet on this one...i've also taken calculus-based physics in college. although i am not a research engineer with 30 yrs experience, i don't think sylvan has posted anything that is incorrect...he is just repeating laws of physics.

Thank you gibblet and sho-me_bhntr !!!

Yep,, the laws of physics can't be argued, it's just the way things are on this earth. I think Dr. Ashby was more concerned with broadhead design in some of his remarks about penetration in flesh. Your bow will only do so much, pick an arrow that will give you what you're looking for. A light arrow will give you the flat shooting advantage and it will cost you some energy and make your bow noisier. A heavy arrow will give you the most energy to expend into your target and make your bow quiet but you'll have to worry a bit more about trajectory. Somewhere in between the extremes there's an arrow for you

[/quote]
I'm can't remember his exact wording, so if efficiency is not the correct term then I'm open to a better one.

But............ the fact remains that there are bows that will shoot a lighter arrow with more KE than a heavier arrow under the exact some shooting conditions; i.e. same bow, same draw weight, same draw length...only the arrow changed.

I've seen it and so has he.

Now as to the merits of KE vs M........I think its a much belabored, over emphasized debate that is only an issue with the most marginal of equipment or the largest of game, neither of with which I'm likely to be confronted.

Generally,however, I subscribe to the Arthur P philosophy. I leave my just for play hot rod arrows by the chronograph, and my heavier work arrows in my quiver.