Momentun charts vs KE charts?

[shortstroke 91]

Is there a Momentum chart equivilent to the KE charts we're so used to? I'm just curious if it's ever been made. My average speed is around 150-160fps (depending on the bow)with a 550 grain arrow and thought a recommended animal MO chart might be helpfull.

[acadian archer]

chart would be interesting but I think you can kill anything in North America with that setup.

[Doug Treat]

It would be pretty easy to make your own chart.  There are a couple different ways to figure momentum, one of which figures affects of gravity.  The easier way to do it is this: weight in grains divided by 7000 (this is how many grains in a pound) and then multiplied by the speed ie. 550 gr. arrow @ 160 fps= 550/7000 (.0785714)X 160= 12.571424.  With the same bow you could probably shoot a 600 gr. arrow @ 155 fps so with that arrow you would have 13.285701 slug pound/pounds...(or whatever units they use for momentum :^)

[shortstroke 91]

I've seen the
#30 KE for small game
#40 KE for deer, antelope, black bear
#50 KE for Elk etc.
charts and was looking for a Momentum equivalent.

[wingnut]

The thing is those charts were made by compound people for compound bows shooting light weight arrows.

I used to believe that it was true, until I started hunting with trad bows and shot elk, deer, bear and a bunch of other things with bows that the chart says you can't kill em with.

Your bow is producing 31.3 KE.


Mike

[jsweka]

Doug - How does gravity affect momentum?  Is it that they really try to account for friction due to wind resistance. I'm just thinking back to my college physics classes in that gravity is a force pulling down on the arrow, not a force pushing against the arrow like wind resistance.

In the end I somewhat think we get a little too hung up on KE and momentum.  Doesn't matter what your setup putting out if the arrows don't fly true or you can't hit your mark.  KE and momentum should be a secondary consideration IMO.

[Dr. Ed Ashby]

Momentum = mass (in grains) multiplied by velocity if fps then divided by 225,218.

The figure 225,218 represents 7000 multiplied by 32.174. The 7000 converts the grains of arrow mass into pounds. 32.174 is the Gravitational Constant (Gc).

If you have an Excel Spreadsheet and you let block B:1 = arrow mass in grains and block B:2 = arrow velocity in feet per second then the formula to enter in block B:3 (in order for it to automatically calculate the momentum as you change either/or the arrow's mass or velocity and return the answer in block B:3) is:

=Sum(B1*B2)/225218

Then you'll have your own momentum calculator.

If you like you can set up the next block; block B4; to automatically calculate the arrow's KE too. The formula to enter in block B4 in order for it to simultaneously calculate the KE is:

=Sum(0.5*B1)*(B2*B2)/225218

In the A column you can enter the labels for each field in Column B; ergo, block A:1 would be the lable "Enter arrow mass in grains"; A:2 would be "Enter arrow velocity in feet per second; A:3 would be "Arrow Momentum equals:"; and A:4 would be "Arrow Velocity equals:"

It's a wise idea to lock the two formula cells; cells B:3 and B:4 to prevent accidentally entering something in them and wiping the formula out. look in the "help' menu for info on how to lock the cells.

Hope that helps,

Ed

[Hot Hap]

My head hurts-Hap

[George D. Stout]

I think I have an old EKG chart lying around somewhere.  8^).

[Jason R. Wesbrock]

Shortstroke,

I agree with Wingnut. The problem with a lot of those Ke or momentum charts, is that they don't have a lot of basis in reality. I remember reading somewhere that 65 foot-pounds is a minimum for moose. I blew through my bull with around 41 foot-pounds.

When in doubt, look at what people have historically used to kill the species you are after. That will tell you what you need.

[flatlander37]

I agree with Hap.  My head hurts too.  Ya just gotta wonder sometimes if the indians were worried about this stuff when they were hunting buffalo!   :D