Postby Mike Habib » Mon Dec 13, 2004 10:27 pm
"Pope and his friends shot Grizzly and Kodiak Bears, bull moose, male Eland, all with longbows. An Archer named Howard Hill did shoot an elephant, again with a longbow, though this time an American longbow."
That's awesome; I'm impressed. I need to get a hold of that reference. Taking shots at large bears takes guts; if you end up needing additional shots (likely) it could get ugly. Impressive nerve and aim obviously involved.
"What is you refereance for the nature of the animals speed deflecting arrows?"
This is actually a prediction based on physics and vector-based analysis, not a specific reference. I would love to see anyone bring actual references to bear to help support and/or refute it.
The argument goes something like this:
When an arrow strikes a target a force equal to the impact force travels down the shaft of the arrow, naturally. Yay for Newton.
Now, if the target is stationary or traveling along a line that is parallel to the arrow's path (straight on from front or behind), the force vector is still along the shaft of the arrow, though the total sum vector is obviously larger if the target is approaching (the difference in velocity between arrow and target is greater).
If, however, the target is moving at an oblique angle relative to the arrow (likely, unless you like standing in the path of charging calvary), then there are vectors in two directions. One from the impact reaction force (as before), but also one in line with the motion of the target (also same as before, but now it's not in the same direction as the impact reaction force). It makes more sense on a diagram, so drawing it out helps.
The sum of these two vectors will now NOT point directly down the shaft of the arrow, but will be oblique to it. This means that the reaction force sum will tend to push the arrow to the side on impact, as well as push back on its axis.
Because the front of the arrow is slowed more quickly (it's contacting the target), this will tend to make the arrow spin (the back will kick out to the side). We see this as a richochet.
The size of the vector resulting from the momentum of the target (not the impact reaction vector), depends on the speed of the target.
Now, keep in mind that this only matters, in reality, if the target has armor. If it does not, the tip will bury in the soft tissue too fast to deflect, though the rear half will still feel a deflection. In this case, it will be felt as a cantelever bending moment (because the head is fixed), and the arrow may break (as in the above posts).
Cheers,
--Mike Habib
Michael Habib
Center for Anatomy and Evolution
Johns Hopkins School of Medicine
habib@jhmi.edu