This is what I'm talkin about!

[michihunter]

BT- What you are grasping is a falsehood. Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum which an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

Momentum = mass x velocity

So how can you say that it has no premise? Please expound.

[michihunter]

If what you say is true, then the same can be said for KE which is scalar quality which encompasses ALL energy and cannot be picked apart into the pieces that make it up.

RE:
By definition, kinetic energy is the capacity to do work. It is the TOTAL ENERGY of a body in motion. K.E. is scalar, or non-directional, in nature. As applied to an arrow in motion, K.E. includes such things as: radial energy due to arrow flexion, rotational energy due to arrow spin, sonic energy due to vibration, heat energy due to friction, and potential energy (all other remaining energy).

[BT]

Yes
As I said .... you have to work within parameters or nothing can be determined.
That is why I listed the momentum table in the section with other tools on the site.
Something is better then nothing

[royden]

Wow - you two ever get into any philosophical debates After it's all done I want the Layman's Kinko's Notes.

I'm slightly lost though ... both momentum and KE describe an arrow in motion. KE (according to Mitchi - I haven't gone to my old physics book and checked him out) includes all the energy in the arrow. Once the arrow is moving how much E is lost to noise, flex, friction, etc.?

Enough is lost that the arrow slows down ... does Momentum take that into account?

On the other hand I agree with BT for newer compounds shot above 60#'s at North American critters - who cares? We're talking about how far in the dirt we shoot right? For women, kids, and african cape buffola shooters I would really like to know some solid take it to the bank kinda numbers.

[BT]

Michi can provide the numbers....I am getting dead tired on this one ;D
But to answer the question simply .... for women,children and cape shooters .... weight rules.
That is to say that you have to assess the ability of the bow which means knowing its flat flight potential then reduce that by 20 - 25% by the addition of weight.

Thats a good rule of thumb and it will give that bow what michi strives for .... balance.

[michihunter]

royden said:

Wow - you two ever get into any philosophical debates After it's all done I want the Layman's Kinko's Notes.

I'm slightly lost though ... both momentum and KE describe an arrow in motion. KE (according to Mitchi - I haven't gone to my old physics book and checked him out) includes all the energy in the arrow. Once the arrow is moving how much E is lost to noise, flex, friction, etc.?

Enough is lost that the arrow slows down ... does Momentum take that into account?

.

By definition and equation - NO. KE is not part of the Momentum equation. Velocity(fps) and Mass(wt. in gr) are the only factors.

But you are mistaking about KE describing an arrow in motion. KE is defined as the work needed to accelerate a body of a given mass from rest to its current velocity. In other words, it's basically saying this is how much energy is needed to produce a specific fps for a specific mass. It's more of a theoretical description than an actual description. Once the arrow is in motion, momentum is the actual work being applied. In order to understand the difference, you must first understand the difference between scalar quantities and vector quantities. KE is scalar. Momentum is vector. ;)Scalars are quantities which are fully described by a magnitude alone. Vectors are quantities which are fully described by both a magnitude and a direction. Hope that helps.

[royden]

michihunter said:

By definition and equation - NO. KE is not part of the Momentum equation. Velocity(fps) and Mass(wt. in gr) are the only factors.

But you are mistaking about KE describing an arrow in motion. KE is defined as the work needed to accelerate a body of a given mass from rest to its current velocity. ..... Once the arrow is in motion, momentum is the actual work being applied. In order to understand the difference, you must first understand the difference between scalar quantities and vector quantities. KE is scalar. Momentum is vector. ;)Scalars are quantities which are fully described by a magnitude alone. Vectors are quantities which are fully described by both a magnitude and a direction. Hope that helps.

Ok ... I wrote my post wrong .... oops I realize KE is not used in the momentum equation.

Let me see if I got it straight. KE is the amount of energy produced when the bowstring is released ... momentum is the amount of energy the moving arrow has.

Is the E required to stop the arrow the same as momentum?

Still I wonder - does momentum take into account Energy lost from the moving arrow due to friction, vibration, arrow flex, etc.? Or is momentum the perfect arrow in a vacuum?

[michihunter]

I guess it would be in a vacuum due to the other factors involved in determining such a thing(re: resistance). But with all equal, it's still a good indicator of what force is applied at impact. KE is the "capacity" of energy that can be derived by the bowstring, arrow and resistance(which is never taken into account ) when determining the equation. Thus to me it is a more broad and inexact than momentum. And keep one thing in mind here, energy is NEVER lost (only transferred)!!

[royden]

So what your saying is KE is the theoretical output of an arrow/bow combination - and may be inaccurate due to other energy drains.?

If that is the case then why is KE measured from a moving arrow that has already left the bow?

gotta run!

[michihunter]

Because the only way to make the equation work is by speed being a part of it.