"Momentum"
07-30-2008, 08:40 AM
#21
Giant Nontypical
Join Date: Feb 2003
Posts: 5,716
RE: "Momentum"
No, I'm just saying that "momentum" is a term that gets tossed around all-too-often by people who have no idea what in the blue hell it is. They might as well be telling us about the Tooth Fairy or Puff the Magic Dragon.
All they know is that one of their internetidols said one time that "momentum is what I use." So they've been repeating it ever since, despite having no blessed clue what it is.
All they know is that one of their internetidols said one time that "momentum is what I use." So they've been repeating it ever since, despite having no blessed clue what it is.
07-30-2008, 08:46 AM
#22
Nontypical Buck
Join Date: Jun 2006
Location: Southeast, VA
Posts: 2,119
RE: "Momentum"
ORIGINAL: HuntingEd
Jeff think about it this way:
Energy is the ability to do work, which is force times distance (F*ds).
Momentum is defined as mass times velocity (m*v).
Mr Isaac Newton discovered in his second law of motion that force is equal to the rate of momentum change with time, F=m*dv/dt, for constant mass. Now since distance ,ds, = v*dt, and incremental KE of motion = F*ds, then substituting, KE= (m*dv/dt)v*dt = m*v*dv. Integrating , KE=1/2m*v squared.
In other words. KE ismore important!!
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
Momentum Truck = 1000
Momentum Ball = 1000
KE truck = 500
KE Ball = 500,000!!!!
Now take this to an arrow and its purpose. How does an arrow due its damage? It CUTS during penetration. IT doesnt create damage through blunt impact like a bullet.
Higher KE gives you Higher penetration because KE is ability to do work (ie. damage),
IMO, I'll take more KE because it gives you more energy to cut through bone and tissues. Becase I rarely make a perfect shot between the ribs.
Do a test. Shoot a 100 grain tip at your target. then a 125.
See which one penetrates deeper, it will be the one w/ more KE.
You also need to take into account that more mass increases the storage of energy
the amount of energy you bow can produce doesnt change, so a lot of energy is lost on a light arrow due to noise, vibration etc. So more often than not a heavier arrow will have higher momentum & KE because of this.
But you then trade off the ablity to shoot flat! So its personal preference.
Jeff think about it this way:
Energy is the ability to do work, which is force times distance (F*ds).
Momentum is defined as mass times velocity (m*v).
Mr Isaac Newton discovered in his second law of motion that force is equal to the rate of momentum change with time, F=m*dv/dt, for constant mass. Now since distance ,ds, = v*dt, and incremental KE of motion = F*ds, then substituting, KE= (m*dv/dt)v*dt = m*v*dv. Integrating , KE=1/2m*v squared.
In other words. KE ismore important!!
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
Momentum Truck = 1000
Momentum Ball = 1000
KE truck = 500
KE Ball = 500,000!!!!
Now take this to an arrow and its purpose. How does an arrow due its damage? It CUTS during penetration. IT doesnt create damage through blunt impact like a bullet.
Higher KE gives you Higher penetration because KE is ability to do work (ie. damage),
IMO, I'll take more KE because it gives you more energy to cut through bone and tissues. Becase I rarely make a perfect shot between the ribs.
Do a test. Shoot a 100 grain tip at your target. then a 125.
See which one penetrates deeper, it will be the one w/ more KE.
You also need to take into account that more mass increases the storage of energy
the amount of energy you bow can produce doesnt change, so a lot of energy is lost on a light arrow due to noise, vibration etc. So more often than not a heavier arrow will have higher momentum & KE because of this. But you then trade off the ablity to shoot flat! So its personal preference.
07-30-2008, 08:50 AM
#23
Nontypical Buck
Join Date: May 2006
Location: IA/WI/IL
Posts: 1,482
RE: "Momentum"
ORIGINAL: HuntingEd
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
07-30-2008, 08:50 AM
#24
Boone & Crockett
Join Date: Sep 2005
Location: Michigan/Ohio
Posts: 11,682
RE: "Momentum"
Where Quick is correct is KE is KE
70 lbs KE on a Quick 285 grain arrow is the same as 70 lbs KE on my 525 Grain Arrow.
The only differnce is a stiff breeze with blow quicks arrow to MI. This is where today's faster bows come into play. Bows waste energy, the heavier arrow the less energy wasted. I have always wondered what the "best" arrow setup would be on a setup.
The arrow weight that gives you the most KE/speed/momentum?
70 lbs KE on a Quick 285 grain arrow is the same as 70 lbs KE on my 525 Grain Arrow.
The only differnce is a stiff breeze with blow quicks arrow to MI. This is where today's faster bows come into play. Bows waste energy, the heavier arrow the less energy wasted. I have always wondered what the "best" arrow setup would be on a setup.
The arrow weight that gives you the most KE/speed/momentum?
07-30-2008, 08:53 AM
#25
Typical Buck
Join Date: Nov 2007
Location: Panhandle of Texas
Posts: 596
RE: "Momentum"
25 grains probably is not going to slow it down much at all. I changed an arrow by adding 70 grains to the total weight and the speed only slowed by 13fps.
07-30-2008, 08:56 AM
#26
Nontypical Buck
Join Date: May 2006
Location: IA/WI/IL
Posts: 1,482
RE: "Momentum"
ORIGINAL: Germ
Where Quick is correct is KE is KE
70 lbs KE on a Quick 285 grain arrow is the same as 70 lbs KE on my 525 Grain Arrow.
The only differnce is a stiff breeze with blow quicks arrow to MI. This is where today's faster bows come into play. Bows waste energy, the heavier arrow the less energy wasted. I have always wondered what the "best" arrow setup would be on a setup.
The arrow weight that gives you the most KE/speed/momentum?
Where Quick is correct is KE is KE
70 lbs KE on a Quick 285 grain arrow is the same as 70 lbs KE on my 525 Grain Arrow.
The only differnce is a stiff breeze with blow quicks arrow to MI. This is where today's faster bows come into play. Bows waste energy, the heavier arrow the less energy wasted. I have always wondered what the "best" arrow setup would be on a setup.
The arrow weight that gives you the most KE/speed/momentum?
07-30-2008, 09:01 AM
#27
Nontypical Buck
Join Date: Jul 2005
Location: Eastern Shore MD
Posts: 2,487
RE: "Momentum"
ORIGINAL: JoeRE
That is 100% correct, but now lets answer it from an archery perspective. Take that force generated by the truck....and the force generated but the baseball....and concentrate them both in an area the diameter of an arrow. Both of them will kill you. Thats why that example doesnt mean anything when you are talking about a 600 grain arrow flying at 200 fps and a 300 grain arrow flying at 300 fps. Truth is, they both will do the trick. Which one penetrates better? One's got more KE....the other more momentum. I pick one, you pick the other....they both still do the trick.
ORIGINAL: HuntingEd
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
Think about this, you have 1000lb truck moving at1 f/s, and a 1 lb baseball moving at 1000 f/s. Which would you rather get hit buy??
I hope you answered the truck.
More Weight = Slower Arrow = Unkown change in KE and Momentum, because the weight of arrow to speed is not linear. And visaversa w/ less weight an more speed.
So here is the trade-offs as I see it:
SPEED.
When you lower speed, your arrow falls more over a given distance, so you have a higher arc in flight.
When you lower speed you increase the chances of game jumping your string, and ducking an arrow, yet heavier arrow is quieter...
Its all PERSONAL PREFERENCE, although we have to come up w/ a formula that shows the optimum set-up. IE where you get a lot of KE w/ great speed...
Probably just takes a lot of tinkering.
07-30-2008, 09:02 AM
#28
Nontypical Buck
Join Date: Aug 2006
Location: Southern MD
Posts: 2,520
RE: "Momentum"
ORIGINAL: jackflap
I lost 8fps with just 25 gr addition. Not doubting you at all. Just makes me realize that I must have an antiquated and/orwimpy set up. I do shoot an older bow and should I dare say a Matthews.
25 grains probably is not going to slow it down much at all. I changed an arrow by adding 70 grains to the total weight and the speed only slowed by 13fps.
It may have to do with the more efficient transfer of energy from bow to arrow when using a heavier arrow. When I went from a lighter arrow to the 533gr arrow my bow's energy transfer efficiency went up.
07-30-2008, 09:03 AM
#29
Dominant Buck
Thread Starter
Join Date: Oct 2005
Location:
Posts: 21,043
RE: "Momentum"
I have always wondered what the "best" arrow setup would be on a setup.
The arrow weight that gives you the most KE/speed/momentum?
The arrow weight that gives you the most KE/speed/momentum?
Its all PERSONAL PREFERENCE, although we have to come up w/ a formula that shows the optimum set-up. IE where you get a lot of KE w/ great speed...
I HAVE to assume that 70+FPKE is nothing to sneeze at......and trust it, at some point.....UNLESS someone can tell me something more "optimal".
07-30-2008, 09:06 AM
#30
Boone & Crockett
Join Date: Sep 2005
Location: Michigan/Ohio
Posts: 11,682
RE: "Momentum"
When I went from a lighter arrow to the 533gr arrow my bow's energy transfer efficiency went up.