Comments on: Building a better bulletproof vest http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/ Presenting the fact and fiction of tomorrow since 2001 Sat, 19 May 2012 23:03:43 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: george http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/comment-page-1/#comment-16986 george Thu, 20 Nov 2008 13:55:54 +0000 http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/#comment-16986 I agree totally docduke. Do bullet proof vests protect from taser stun guns I agree totally docduke. Do bullet proof vests protect from taser stun guns

]]> By: docduke http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/comment-page-1/#comment-4807 docduke Fri, 02 Nov 2007 18:49:32 +0000 http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/#comment-4807 You are most welcome! I spent about a decade designing and building "electrothermal guns." I continue to be amazed how often the basics of science are overlooked when an appealing story line has been constructed. You are most welcome! I spent about a decade designing and building “electrothermal guns.” I continue to be amazed how often the basics of science are overlooked when an appealing story line has been constructed.

]]> By: Edward Willett http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/comment-page-1/#comment-4796 Edward Willett Fri, 02 Nov 2007 14:52:19 +0000 http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/#comment-4796 Interesting. Thanks for the explanation! Interesting. Thanks for the explanation!

]]> By: docduke http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/comment-page-1/#comment-4790 docduke Fri, 02 Nov 2007 13:48:44 +0000 http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/#comment-4790 That is precisely what I am saying. Newton's second law is usually stated F=m*a. Its meaning is clearer as F= delta p. The force applied to a body is equal to the change in momentum of the object applying the force. If a bullet is stopped by the body, it transfers a momentum equal to the mass of the bullet times its velocity on impact. If the bullet arrives and springs off the surface of the body at a velocity equal to its incoming velocity but opposite in sign, the change in bullet momentum is TWICE that of a bullet coming to rest. All of that momentum is transferred (by the spring) to the body. There is nowhere for the momentum to go except into the body. The dynamics of "spreading out" the impact momentum is limited by the speed of sound in the "spring" material, and the transfer of momentum to the body is controlled by the deformation of the bullet, which occurs at the speed of sound in the metal. The momentum really cannot, for physics reasons, be spread very far laterally in the time it takes the bullet to impact. For very fundamental physics reasons, this proposal is fantasy trying to ride the nanotech funding bubble. That is precisely what I am saying. Newton’s second law is usually stated F=m*a. Its meaning is clearer as F= delta p. The force applied to a body is equal to the change in momentum of the object applying the force. If a bullet is stopped by the body, it transfers a momentum equal to the mass of the bullet times its velocity on impact. If the bullet arrives and springs off the surface of the body at a velocity equal to its incoming velocity but opposite in sign, the change in bullet momentum is TWICE that of a bullet coming to rest. All of that momentum is transferred (by the spring) to the body. There is nowhere for the momentum to go except into the body.

The dynamics of “spreading out” the impact momentum is limited by the speed of sound in the “spring” material, and the transfer of momentum to the body is controlled by the deformation of the bullet, which occurs at the speed of sound in the metal. The momentum really cannot, for physics reasons, be spread very far laterally in the time it takes the bullet to impact.

For very fundamental physics reasons, this proposal is fantasy trying to ride the nanotech funding bubble.

]]> By: Edward Willett http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/comment-page-1/#comment-4740 Edward Willett Thu, 01 Nov 2007 22:40:27 +0000 http://futurismic.com/2007/10/31/building-a-better-bulletproof-vest/#comment-4740 I don't follow. The equal and opposite reaction is precisely what makes the bullet rebound: it's just that the energy absorbed by the material at the moment of impact is released by the material springing back into shape, instead of being transferred to whatever is on the other side of it. If I'm wearing a suit made of, say, wood, and you hit me in the side with a baseball bat, a lot of that force is going to be transferred through the non-springy wood to my ribs, even though some of it will be absorbed and spread out trough the wood. If I'm wearing a suit made of springy rubber, your bat will bounce off and far less of that force will be transferred. You seem to be saying that the force of the impact would be doubled by the springy suit. I don’t follow. The equal and opposite reaction is precisely what makes the bullet rebound: it’s just that the energy absorbed by the material at the moment of impact is released by the material springing back into shape, instead of being transferred to whatever is on the other side of it. If I’m wearing a suit made of, say, wood, and you hit me in the side with a baseball bat, a lot of that force is going to be transferred through the non-springy wood to my ribs, even though some of it will be absorbed and spread out trough the wood. If I’m wearing a suit made of springy rubber, your bat will bounce off and far less of that force will be transferred. You seem to be saying that the force of the impact would be doubled by the springy suit.

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