From: dc-cycles-digest-request@XXXXXX (The dc-cycles list administrator) To: dc-cycles@XXXXXX Errors-To: dc-cycles-digest-request@XXXXXX Subject: dc-cycles digest for 11/24/05 ------------------------------------------------------------------------------ __ /-----\ __ 'dc-cycles' is an unmoderated email discussion list (__\/ _____ \/__) about motorcycling in the Washington D.C. area. =( \___/ )= \ ___ / An archive of the dc-cycles list is available at: | / _ \ | http://www.dc-cycles.org/ \ || || / \|| ||/ Subscribe/unsubscribe requests should be sent to: \| |/ dc-cycles-digest-request@XXXXXX |_| ------------------------------------------------------------------------------ Date: Wed, 23 Nov 2005 19:32:31 -0500 From: Michael Jordan To: dc-cycles@XXXXXX Subject: Re: [dc-cycles] Couple letters in the WaPo > Stopping from 1 mph in an inch is no big deal. Stopping from 70 mph in an > inch is. Was it the 70 mph that killed you, or the inch? Actually, it's "G" force over time. 1MPH in 1" is, as you said, no big deal, but you could postulate a distance that stopping from 1 MPH would be a big deal (I have neither the math nor the anatomical knowledge to determine what that distance would be). -- Michael J. '86 SRX-6 '93 GSX1100G '03 DL1000 AMA IBA #3901 USAF (Ret) NRA etc. _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. (_)=='(_) (_)=='(_) (_)=='(_) (_)=='(_) Date: Thu, 24 Nov 2005 01:07:16 -0500 To: Michael Jordan , dc-cycles@XXXXXX From: "Mike B." Subject: Re: [dc-cycles] Couple letters in the WaPo At 07:32 PM 11/23/2005 -0500, Michael Jordan wrote: >> Stopping from 1 mph in an inch is no big deal. Stopping from 70 mph in an >> inch is. Was it the 70 mph that killed you, or the inch? > >Actually, it's "G" force over time. Um, sort of, but not always and that's not a good way to phrase it. "G force" is acceleration (1 G = 9.8 m/s**2). Acceleration over time is velocity. >1MPH in 1" is, as you said, no big >deal, but you could postulate a distance that stopping from 1 MPH >would be a big deal (I have neither the math nor the anatomical >knowledge to determine what that distance would be). I don't think so. The problem isn't the distance, or primarily the speed, or even necessarily the acceleration...it's the energy. There isn't enough energy in a person moving at 1 mph to do much harm to that person. There is plenty in one doing 70 mph to kill them...if it's applied in the wrong way. Humans aren't rigid bodies, so you can't stop them arbitrarily quickly like you could if they were. Run a human into a solid object and the leading edge may stop instantly (for all practical purposes), but the rest keeps coming. this results in distortion of the body, which eats up energy in friction and other ways, but it also extends the impact time for the "rear" parts of the body, thus lowering the acceleration for those parts. The various bonds that keep us together are elastic up to a point, and stretching them eats energy, then they rebound, stretch again, eat more energy, etc.. Sort of like dropping a water balloon that doesn't break. We know from experience what sort of accelerations you can subject a buman to, and for how long, without damage. I've run into solid objects at more than 1 mph, and stopped in less than 1" before, The object in one case when I was 7 was a concrete building, and it didn't move noticeably. I was at a low running speed (3-4 mph at least). I'm sure parts of me stopped instantly, and other parts kept moving for a bit longer, distorting my shape a bit for a fraction of a second until it all rebounded (people are not rigid objects). I sustained a minor injury (cut on the head), and had some pain, but didn't require more than some washing and a bandaid. If that same event had happened at 70 mph I'd probably have been killed. The acceleration matters to the extent that too much won't allow the energy to be dissipated safely. So long as there isn't enough energy to do harm, you can stop as quickly as you like (within the limits of stopping a non-rigid body like ours). Once there's enough energy to do harm, you have to keep the forces used to dissipate it below the structural failure level...at that point the (de)acceleration rate starts to matter....and too many "Gs" will break us. The acceleration the human body can sustain depends on how long you apply it. We can take 1 G indefinitely. We can take 3 Gs for many minutes with some training (ala Apollo liftoff). We can take 10 Gs if in great shape, the right position and trained to handle it, for many seconds (ala F-16 pilots in a tight turn or an aerobatic pilot in certain maneuvers). We can take 20-25 Gs for a few milliseconds (ala a college football tackle). Get much over that, even for a few milliseconds, and you start getting structural failure. With the wrong body position you can get localized failures even sooner of course (broken bone in a bad tackle for instance). It's been a while since physics class, and it's late, but if I recall correctly (and if http://id.mind.net/~zona/mstm/physics/mechanics/kinematics/EquationsForAccel eratedMotion/EquationsForAcceleratedMotion.htm is being read properly), the equation for accelerated motion we need is: Vf**2 - Vi**2 = 2ad where Vf is final velocity (zero in our case), Vi is the initial velocity (70 mph), a is acceleration and d is the distance over which the acceleration takes place to change the velocity from Vi to Vf...in our case, 1". Do the math, adjust the units and for a 70 mph to zero acceleration over one inch you get 1966.97 Gs...i.e. "splat". If we repeat it for the 1 mph case we get about 7Gs...i.e. probably no noticeable damage. The 7 gs only lasts for about 6 milliseconds. -- -- Mike B. '04 FLSTCI (H-D Softail Heritage Classic with EFI for the non-Harley folks) Learning from your mistakes is good. Learning from someone else's mistakes is better. _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. (_)=='(_) (_)=='(_) (_)=='(_) (_)=='(_) Date: Thu, 24 Nov 2005 07:05:16 -0500 From: Michael Jordan To: dc-cycles@XXXXXX Subject: Re: [dc-cycles] Couple letters in the WaPo > Long post from Mike B. snipped Point taken. Told ya that I didn't have the math :-) -- Michael J. '86 SRX-6 '93 GSX1100G '03 DL1000 AMA IBA #3901 USAF (Ret) NRA etc. _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. 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Kyrene Road > Tempe, Arizona 85283 > > Email list management powered by http://MailerMailer.com > _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. (_)=='(_) (_)=='(_) (_)=='(_) (_)=='(_) Date: Thu, 24 Nov 2005 12:57:06 -0500 From: "John M. Stafford" To: Saints SC Mailing List , DC-MD-PA-VA Scooters Mailing List , , Central VA Scooters Mailing List CC: dc-cycles Mailing List , Subject: [dc-cycles] Vote for a New Welcome to Virginia Signs To honor Virginia's 400th Anniversary in 2007 the state of Virginia will be revising the signs that sit at the entrance to the state along all major highways for the first time in a half-century. The state is giving all residents the opportunity to vote on your favorite design. To cast your ballot just go to: http://virginiadot.org/infoservice/is-WelcomeSigns.asp I hope everyone has had a happy and safe Thanksgiving. Enjoy, John M. Stafford _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. (_)=='(_) (_)=='(_) (_)=='(_) (_)=='(_) Date: Thu, 24 Nov 2005 13:33:43 -0500 To: Michael Jordan , dc-cycles@XXXXXX From: "Mike B." Subject: Re: [dc-cycles] Couple letters in the WaPo At 07:05 AM 11/24/2005 -0500, Michael Jordan wrote: >> Long post from Mike B. snipped > >Point taken. Told ya that I didn't have the math :-) It's not a simple problem. I hope I got it right enough for all practical purposes. ;-) -- -- Mike B. '04 FLSTCI (H-D Softail Heritage Classic with EFI for the non-Harley folks) Learning from your mistakes is good. Learning from someone else's mistakes is better. _ _ _ _ .-.-.=\-. .-.-.=\-. .-.-.=\-. .-.-.=\-. (_)=='(_) (_)=='(_) (_)=='(_) (_)=='(_) Date: Thu, 24 Nov 2005 17:11:56 -0500 From: Aki Damme To: dc-cycles Subject: [dc-cycles] Snow in Herndon? I just read on nbc4.com that there was snow Wednesday night in the DC area, as much as one inch west of DC. Anyone know how much we got in the Herndon area? And if any of it is still there? -aki (who's obviously not in-area) -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.1.362 / Virus Database: 267.13.7/181 - Release Date: 11/24/2005