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Does Kinetic Energy = Penetration?

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Does Kinetic Energy = Penetration?

Old 08-14-2002, 10:53 AM
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Default RE: Does Kinetic Energy = Penetration?

Bob, 45 pounds of KE = just that, 45 pounds of KE at 5 yards and at 45 yards. It doesn't matter.

As to acceleration vs deceleration, Once the arrow nock leaves the string the arrow starts decelerating. There is no more acceleration. It can't happen! If you believe so, please explain how this occurs.

If the arrow had 45 pounds KE when it left the bow and your question dealt with 5 yards and 45 yards with this same arrow, I don't think there is an issue as it won't be 45# KE at either location.

My 2 cents
Greg

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Old 08-14-2002, 11:07 AM
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Default RE: Does Kinetic Energy = Penetration?

It would be the 5 yard shot. As I stated it is still excelerating, meaning that it still has much of it's stored energy in the arrow that will be dispersed before coming to a stop. On the other end, on the longer shot, the arrow has already peaked in KE in it's flight and it lost most of it's stored energy. But see what I mean about how deceiving the thought of KE alone = penetration.
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Old 08-14-2002, 11:09 AM
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Default RE: Does Kinetic Energy = Penetration?

amogreg, are you saying that the arrow does not accelerate and its fastest flight is when it is still on the bow?

Edited by - BobCo19-65 on 08/14/2002 12:11:03
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Old 08-14-2002, 11:13 AM
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Default RE: Does Kinetic Energy = Penetration?

It's fastest point is just as the nock leaves the string. At that point gravity and air resistance start slowing it down and there is nothing providing further propulsion.

"Getting close to the game is the joy of Bowhunting for me, the harvest is a bonus."

Live 15 ft Python after eating a small Antelope!
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Old 08-14-2002, 11:19 AM
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Default RE: Does Kinetic Energy = Penetration?

Good point greg. I was thinking about that...that's what I always thought...once it starts...it is decelerating...but as to his question, I was looking at it as a 5 yard shot with 45lbs of KE vs a 40 yd shot with the same KE...I think the 5 yd shot would probably out penetrate the 40 yd shot(but obviously it wouldn't be out of the same setup) so I guess it's not really comparing apples to apples totally.

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Old 08-14-2002, 11:25 AM
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Default RE: Does Kinetic Energy = Penetration?

Remember (I don't remember the formula) that KE = weight * Speed and there is a constant there so 45# KE should perform to the same level all things considered and if there is a difference it will be the heavier arrow that penetrates further due to the momentium carried.

Remember back to physics and all those equasions and formulas. Here is where they come into play.

Again I don't have access to the readily right now.

Greg

"Getting close to the game is the joy of Bowhunting for me, the harvest is a bonus."

Live 15 ft Python after eating a small Antelope!
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Old 08-14-2002, 11:25 AM
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Default RE: Does Kinetic Energy = Penetration?

I was always under the assumption that an arrow had its peak flight about 10 yards out. But I could be wrong.
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Old 08-14-2002, 11:39 AM
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Default RE: Does Kinetic Energy = Penetration?

Bob..I think you are maybe confusing it with trajectory. In any case...yes there are alot of factors that make up penetration, other than just KE, that is for sure

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Old 08-14-2002, 11:48 AM
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Default RE: Does Kinetic Energy = Penetration?

Bob,
Think about a car even on a hill once you stop pressing the gas the car starts slowing down unless the weight of the car and the grade of the hill allows gravity to continue the acceleration.
In order for anything to accelerate it must have a force acting on it. The car, the force = the engine. The Arrow the force = the limbs of the bow through the bowstring.
Once the force is no longer imparted the acceleration no longer occurs and if we were in a total vacum with no gravity then there would be no deceleration as there would be nothing to act against the force already imparted on the object and stored as stored energy(I believe this is the Kenetic Energy).
When the arrow impacts the KE is used and this use of stored energy is what drives the arrow into the medium to the level of the stored energy - penetration.

The mass(weight) of the object at this point is what determines how effective this transferance of energy is and this determines penitration as a lighter object requires less energy to stop and a heaver object more. The resistence of the target being penetrated determines how much energy is used for this penetration and this determines how far the object penetrates.

I hope I described this accurately and if I didn't please don't hesitate to correct me.

Greg


"Getting close to the game is the joy of Bowhunting for me, the harvest is a bonus."
Live 15 ft Python after eating a small Antelope!

Edited by - amosgreg on 08/14/2002 12:49:38
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Old 08-14-2002, 11:56 AM
  #20  
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Default RE: Does Kinetic Energy = Penetration?

No, I think I understand what you are saying. Basically there is no peak cycle in the accelaration of the arrow. The arrow is basically only decelerating after it leaves the bow. I've never tried it before, but a chono placed one foot away from the shot would read higher than it placed five feet from the shot. Same would hold true for a gun then correct?
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