Naked Science Forum
On the Lighter Side => Science Experiments => Topic started by: jack fulker on 15/10/2011 12:30:02
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jack fulker asked the Naked Scientists:
Dear Chris
I am a Y10 pupil at Archbishop's School in Canterbury. I am doing a science project with 2 of my friends to gain a silver CREST award. Our project is investigating how fat a human being would need to be to protect their vital organs from penetration of an arrow fired by an archer from a known distance. We are trying to build a replica human which would accurately represent the human skin and fat to use as a test subject. We wondered if you could help us in any way with our project.
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Thank you and best wishes,
From Jack Fulker
What do you think?
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http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/how-fat-would-you-have-to-be-to-stop-a-bullet/
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I think this is a great project but have you considered the following:
1, Obesity is not normally a survival factor in combat situations.
2, Areas of the body that tend to accumulate the most fat do not cover the most vital organs we have such as our heart, brain, or spine. This would indicate that being fat has no evolutionary survival benefit.
3, Someone large enough to stop an arrow with body fat is going to be so big that they actually have more chance of being struck by arrows due to their larger surface area.
4, Mobility might be a problem and although someone might be able to stop an arrow with fat they are not going to be leaving the field of battle in a hurry and again would probably be stuck with more arrows as a result of that.
5, The people who design weapons, design them to kill. Throughout history opposing forces have always tried to protect themselves using armor built to stop arrows and so on. All this leads to is the development of weapons that can overcome the defensive strategies of opponents. One fine example of this is the English Longbow which was able to penetrate the best armor of the day.
Good luck with your project and I look forward to hearing about your results and even a video on youtube for your ultimate experiment.
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When you look an abdominal MRI of an obese person, the cross section of the bowels, stomach, liver, etc are essentially the same as a thin person.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fmpl.phhp.ufl.edu%2Faging%2Fimages%2Fabdomen_cross-sectional_weighted_MRI.png&hash=8c954c950f9892d52d98b64a7f82e5d4)
So, while the obese individual may present a bigger target, if the arrow would hit a portion of the person that would not even be part of the body of a thin person, then it likely would only do minimal damage.
That isn't to say that the adipose tissue isn't vascularized. However, the risk from only hitting adipose tissue is much less than hitting aorta, liver, stomach, bowel, or other organs.
There are many types of arrows including blunt tips, target tips, and broadhead tips. The broadhead tips are often sharpened as sharp as your shaving razor.
Likewise, there are different types of bows, generally classified by the amount of strength to pull the string back. And, of course distance from the target would be an issue too.
One should be able to calculate the rate of slowing as the arrow slices though adipose tissue, as well as forces necessary to penetrate the abdomen, bowel, aorta, or other organs.
I'm thinking that it would take a whole heck of a lot of adipose tissue, and only at the maximum range of the arrow to stop a good sharp broadhead. But, I'm not sure where you would find useful experimental data.
This would be an excellent question to ask Mythbusters. Pigs have a lot of backfat, so a butcher should be able to supply you with a bag of pig fat to experiment with. And, you should be able to calculate penetration speed and deceleration with a good high-speed camera.
Then you would just need to figure out how much residual force/speed would be required to penetrate through the abdominal wall, and into, say bowel.