kinetic energy

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scottflesher
 
Posts: 605
Joined: Sun Oct 11, 2009 3:44 pm
Location: SE Ohio

RE: kinetic energy

Postby scottflesher » Tue Jul 20, 2010 12:14 pm

Lot to Learn,
here is an article that I found particuarly interesting. It takes the physics of arrow flight and breaks it into easy to understand terms. Some may a differing opinion with the entire light vs. heavy debate, but it's difficult to disagree with the physics of the equation.

One area to be cognizant of, the faster an object, the more force (air resistance) slowing it down. An arrow going 350 fps, slows down at a faster rate than an arrow going 300 fps all else equal (arrow diamater, etc). Another area to consider is that because a faster arrow slows down at a quicker rate, you are at some point (distance wise) going to reach a break even point. When a bow is rated for speed, it's typically rated at point blank range as the speed of the arrow slows down the further down range you get. I doubt many of us shoot deer at point blank range with our bow.
Bottom line, it's a delicate balance of speed and arrow mass (weight) that we must maintain, with an edge to the mass side of the equation. Either extreme is not desireable per most archers. On one hand, being overly fast can create more bow noise (negative) and a flatter trajectory (positive), but on the other hand, shooting too heavy of an arrow means a quieter bow (positive) but an increased importance on accuracy --lobbing trajectory (negative). I don't care how heavy the arrow is, if your lobbing it in like a football hail mary, chances are the animal will have an opportunity to move and KE doesn't mean a whole lot when you've missed the animal.

http://archeryreport.com/2010/04/heavy- ... eed-power/

Lot to Learn
 
Posts: 243
Joined: Sat Jul 12, 2008 4:39 pm

RE: kinetic energy

Postby Lot to Learn » Wed Jul 21, 2010 2:50 am

Thanks Scott, this is exactly what I was hoping to find.  I am a math geek so I am a little disappointed the physics section is "coming soon" but the info is what I was looking for.  I have read from several sources and a few people on this board also pointed out the velocity of the lighter arrow dropped off faster, to me, and I was wrong, that was counter intuitive. I was thinking the only two forces that could act on the arrows would be gravity and wind resistance(drag) which is correct, however, I thought the smaller diameter arrow would have less drag, which also may be true, but I did not consider the effect of drag on velocity, which nails the final piece of what I was pulling my hair out over.   In my mind, looking at the equation for kinetic energy, since the velocity is squared I was thinking any increase in velocity would have a much greater effect on energy than an even bigger increase in mass, since that was just a linear increase.  Thanks again for the article. 

scottflesher
 
Posts: 605
Joined: Sun Oct 11, 2009 3:44 pm
Location: SE Ohio

RE: kinetic energy

Postby scottflesher » Wed Jul 21, 2010 12:18 pm

anytime. I cannot wait for the next sections myself.

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