I havent bothered to figure the amount of momentum you are getting. Quite bluntly I probably wont either.

As per this ducking at gravity, I still disagree. Even after looking at Art' s info which would more closely relate to whats happening, a deer is using muscles to move. As it would be no different if you were on all fours. Hence there is more happening then just gravity. They' d have to be standing, have there legs whipped out from underneath for it to only be gravity.

as per your test, did a human shoot that arrow?