Momentum is just a number. Arguably the most important one, yes. You can think of Momentum as a Budget. Some gets spent on air resistance, some on penetration of fur, hide, bone, etc. The more budget available the better.
Using the legal minimum in most states for deer as #40lb draw, and assuming 10 gpp arrow is 400gr traveling at say 180fps is just shy of 0.32 slugs.
If we take Fred Bear at his word that "#45 bow can take any animal in north america" with a well placed shot, assuming 10gpp again, 450gr at 180fps is 0.36 Slugs.
So, it would seem 0.32 is certainly adequate for whitetail. Around 0.36 for larger game such as Moose would probably be marginal at best. Round up to 0.4 slugs for Elk sized animals. Now Lets assume most people trad hunting brow bear are shooting at least #65Lb and 650gr, then we get a Momentum of 0.52 Slugs or more for tough or dangerous animals.
Taken to the extreme, One whole slug is a lot of force for anything that lives (on land). And it can be obtained with a heavy enough arrow based on the above charts.
Keep in mind, its only a momentum budget. A dull or damaged broadhead, additional blades, bone impacts, etc. are going to cost more than a super efficient arrow.
Also note that resistance to motion goes up at the square of speed. This includes air resistance and also flesh. Think about jumping into a lake from a boat, vs jumping into a lake from an airplane. They say water becomes like concrete at high velocities. This is resistance going up in a cubic relationship to speed. Animals and people are made up primarily of water, and arrows are traveling awfully fast. So, adding momentum and taking away speed helps on both ends of the penetration equasion.
Seeing all mammals are built with the same stuff, you don't actually need a very wide variation in momentum between an 80lb pig and an 800lb elk.
Topic: KE and MOMENTUM explained (Read 3070 times)
