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Dr. Mabuse
Septic Fiend

Sweden
9640 Posts

Posted - 09/16/2009 :  07:49:11   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
Originally posted by astropin

I wouldn't have stopped either...no way.

You're right though, the bus drivers statement could make all the difference.

The first verdict (kind of...) is in.
After reviewing my statements and that of my wife, my car-insurance company decided that I wasn't to be held liable for the accident. Any claims from the other car-owner will be referred to his insurance company.

That's a first win. But as they say: "It ain't over 'til the fat lady sings."
At least I have an indication that it's likely to go my way if the police investigation (or the other driver) decides it's time for court.


Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

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Dave W.
Info Junkie

USA
25752 Posts

Posted - 10/24/2009 :  20:50:51   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Hey, math-hounds!

If I've got a model rocket which reaches altitude A (in feet) in L seconds (generally less than 10) and then comes back to Earth on a parachute that slows its descent to P feet/second with a wind of W miles per hour, at what angle R from the vertical should I position the launch rod to try to ensure the least distance between the launch site and the spot where the rocket lands again?

For example, with a vertical launch rod, a rocket that can reach 1,000 feet in 5 seconds, a 20 f/s parachute and a wind of 10 mph, I can expect the rocket to land some 807 feet from the launch site, assuming that the rocket always moves laterally with the same speed as the wind. I want to minimize that distance by tilting the launch rod into the wind, but if I tilt it too far, the rocket will wind up going hundreds of feet in the other direction. So, given A, L, P and W, what would be the equation for the optimal R that would have the rocket landing right where it took off?

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 11/07/2009 :  02:17:26   [Permalink]  Show Profile Send HalfMooner a Private Message  Reply with Quote
I find heartwarming this video, in which an American WWII vet recounts his playing "Lili Marlene" with his trumpet to a German sniper during combat.

Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
Edited by - HalfMooner on 11/07/2009 02:19:23
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Dr. Mabuse
Septic Fiend

Sweden
9640 Posts

Posted - 11/07/2009 :  05:53:48   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
The Police is done investigating the traffic incident I was involved in (see above).
Result: No crime could be substantiated due to conflicting testimonies. Case closed.


Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

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Hawks
SFN Regular

Canada
1383 Posts

Posted - 11/10/2009 :  19:02:34   [Permalink]  Show Profile  Visit Hawks's Homepage Send Hawks a Private Message  Reply with Quote
From FailBlog:

METHINKS IT IS LIKE A WEASEL
It's a small, off-duty czechoslovakian traffic warden!
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Zebra
Skeptic Friend

USA
354 Posts

Posted - 11/11/2009 :  00:07:44   [Permalink]  Show Profile Send Zebra a Private Message  Reply with Quote
Originally posted by Dave W.

Hey, math-hounds!

If I've got a model rocket which reaches altitude A (in feet) in L seconds (generally less than 10) and then comes back to Earth on a parachute that slows its descent to P feet/second with a wind of W miles per hour, at what angle R from the vertical should I position the launch rod to try to ensure the least distance between the launch site and the spot where the rocket lands again?

For example, with a vertical launch rod, a rocket that can reach 1,000 feet in 5 seconds, a 20 f/s parachute and a wind of 10 mph, I can expect the rocket to land some 807 feet from the launch site, assuming that the rocket always moves laterally with the same speed as the wind. I want to minimize that distance by tilting the launch rod into the wind, but if I tilt it too far, the rocket will wind up going hundreds of feet in the other direction. So, given A, L, P and W, what would be the equation for the optimal R that would have the rocket landing right where it took off?
I don't check this thread that often. And if you'd said "physics hound" I wouldn't have read this question. But since you said "math hound", here goes an attempt:

First, a caveat: this does NOT consider any gravitational effects, assumes they are included in the speeds up & down that you gave.

A/P = D (time rocket takes to descend, in seconds)

D + L = T (total time rocket is in the air, during which wind pushes it, in sec)

Change in units for W:
W miles/hr x 1hr/3600sec x 5280ft/1mi = 1.46667 x W in ft/sec

So,
1.46667 x W x T = S (horizontal displacement of rocket, in ft)

Now, comes some *yuck* physics. I THINK what you're looking for in angle R is the angle of a right triangle for which A is the adjacent side (the upward distance) and S is the opposite side (the lateral distance, imagined here up in the air, parallel to the ground, the same distance as the rocket would fall from the launch if shot directly upright). This assumption may not be correct. But, if it is, what you're looking for is given by:

tangent (R) = opposite/adjacent = S/A
tan (R) = (1.46667 x W x T)/A
tan (R) = (1.46667 x W)(D + L)/A
tan (R) = (1.46667 x W)(A/P + L)/A
tan (R) = (1.46667 x W)(1/P + L/A)
(Well, at least the units work out right!)

Which I think means:
R = arctan [1.46667W(1/P + L/A)] - with R headed into the wind, of course

(It's been more than 30 years since I last thought about arctangents - please do double check my work before relying on it to aim a rocket)

Thanks for the opportunity to nerd out on a little math


Edited for clarification of order of operations, and later to fix a boo-boo (had "cot" instead of "tan" for function above). Also, please note that "1.46667" is really "1.46666...")

I think, you know, freedom means freedom for everyone* -Dick Cheney

*some restrictions may apply
Edited by - Zebra on 11/11/2009 00:30:32
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Dave W.
Info Junkie

USA
25752 Posts

Posted - 11/11/2009 :  01:09:33   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by Zebra

Now, comes some *yuck* physics. I THINK what you're looking for in angle R is the angle of a right triangle for which A is the adjacent side (the upward distance) and S is the opposite side (the lateral distance, imagined here up in the air, parallel to the ground, the same distance as the rocket would fall from the launch if shot directly upright). This assumption may not be correct...
Actually, I've given it some thought, and A is more like the hypotenuse. But not quite.

As I discovered to my horror this past weekend, one ignores gravity at one's peril. There was a slight breeze, I tilted the launch rod what I thought was a tiny bit into the wind (less than 5 degrees), and the 1,100-foot flight went sailing at least a couple hundred feet away, horizontally. I could see what was probably a gravity-induced curve in the smoke trail.

And then, damn my luck, the wind reversed direction, and so the rocket is most-likely right now hanging from a very high tree branch in a nearby forest. I lost sight of it as it was descending over some townhouses, and couldn't possibly catch up to it on foot with its massive lateral head-start.

The altitude, A, is only valid for rockets shot straight up into the air. The total path distance will be at least equal to A for rockets launched at some angle, R, but since rocket fins aren't wings, any rocket launched at an angle will begin to change course due to gravity from t=0 on.

And then, thanks to the brutally demonstrated fact that the wind can change direction without warning, I realized this whole mathematical exercise is probably just academic, anyway. Practically speaking, it's probably wisest to launch the rockets straight up, regardless of the wind, and just hope for an easy recovery.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
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Dr. Mabuse
Septic Fiend

Sweden
9640 Posts

Posted - 11/26/2009 :  14:11:20   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
Today I made a visit to the hospital for a CT-scan.

During my last visit to the hospital I told the doctor who was treating me for sepsis that my mother and all her siblings had polycystic kidney disease. He thought that interesting since my sepsis originated from a urinary tract infection, so he ordered a CT-scan.

The scanner was put into had a bit more modern design than the one in the first link. When I figure out how to transfer photos from my mobile phone to the computer, I'll upload it.
I had to drink a lot of extra water, starting last evening. A liter more this morning, then another liter the last half-hour before the scan. And yet another liter and a half extra during the rest of the day.

They also used some radioactive(?) iodine contrast fluid they injected just prior of the scan. I've been told that there are several "side effects" to the contrast, like sensations of intense heat in different body-parts. I didn't feel the first shot at all, and 8 minutes later when I got another dose twice as much I only felt a bit warm to the chest, and the backside of my legs, just below gluteus maximus.
The visit (not including sitting for a half hour drinking water) into the CT-scan room including all preparations and clearing up only took 25 minutes.

Now it's waiting again to hear from the doc...


Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

Support American Troops in Iraq:
Send them unarmed civilians for target practice..
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Kil
Evil Skeptic

USA
13311 Posts

Posted - 11/26/2009 :  15:43:08   [Permalink]  Show Profile  Visit Kil's Homepage  Send Kil an AOL message  Send Kil a Yahoo! Message Send Kil a Private Message  Reply with Quote
Hey Mab. They made you drink that much water? Here they would have given you wine. That's socialized medicine for you...

Uncertainty may make you uncomfortable. Certainty makes you ridiculous.

Why not question something for a change?

Genetic Literacy Project
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Dave W.
Info Junkie

USA
25752 Posts

Posted - 11/26/2009 :  16:17:48   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by Dr. Mabuse

They also used some radioactive(?) iodine contrast fluid they injected just prior of the scan.
Probably radiocontrast iodine.
I've been told that there are several "side effects" to the contrast, like sensations of intense heat in different body-parts.
When I had this done, 24 years ago, the main side effect of the contrast was to "reverse" my digestive system, in the technician's words. Even though I hadn't eaten anything in the prior 24 hours (as I was instructed), I threw up. Go figure. The second-to-worst part of the whole experience was trying to hold onto the previous day's breakfast while the technician yelled at the nurse to get another emesis basin.

The worst part was that as soon as they were sure that I wasn't going to barf again, they made me lay down for the imaging. No rinsing my mouth out or anything, just puke-puke-CT.


- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
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Dr. Mabuse
Septic Fiend

Sweden
9640 Posts

Posted - 11/26/2009 :  22:13:00   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
Originally posted by Dave W.

Originally posted by Dr. Mabuse

They also used some radioactive(?) iodine contrast fluid they injected just prior of the scan.
Probably radiocontrast iodine.
I wasn't sure I heard it right, so I asked the nurse what iodine isotope they used. She looked blank then answered "Iso-what? We use iodine...". That's when I decided it was pointless to ask more technical questions.


The worst part was that as soon as they were sure that I wasn't going to barf again, they made me lay down for the imaging. No rinsing my mouth out or anything, just puke-puke-CT.
How inconsiderate.
Perhaps timing is important. I wasn't injected with the main dose until a few seconds before the scan. Probably because they wanted to make sure the contrast didn't have time to seep into surrounding tissue.

Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder.
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Siberia
SFN Addict

Brazil
2322 Posts

Posted - 12/23/2009 :  16:35:36   [Permalink]  Show Profile  Visit Siberia's Homepage  Send Siberia an AOL message  Send Siberia a Yahoo! Message Send Siberia a Private Message  Reply with Quote
Been awhile since someone posted on this, eh?
Also, any results, Mab? Are you OK?
Also... hi! I'm not dead! And since I had no idea how to announce this grand fact, a post in the water cooler sounds suitable :)

"Why are you afraid of something you're not even sure exists?"
- The Kovenant, Via Negativa

"People who don't like their beliefs being laughed at shouldn't have such funny beliefs."
-- unknown
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Kil
Evil Skeptic

USA
13311 Posts

Posted - 12/23/2009 :  17:48:16   [Permalink]  Show Profile  Visit Kil's Homepage  Send Kil an AOL message  Send Kil a Yahoo! Message Send Kil a Private Message  Reply with Quote
Originally posted by Siberia

Been awhile since someone posted on this, eh?
Also, any results, Mab? Are you OK?
Also... hi! I'm not dead! And since I had no idea how to announce this grand fact, a post in the water cooler sounds suitable :)
Hey Siberia, glad to see that you're not dead! Hope to see you around. You have been missed.

Uncertainty may make you uncomfortable. Certainty makes you ridiculous.

Why not question something for a change?

Genetic Literacy Project
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marfknox
SFN Die Hard

USA
3739 Posts

Posted - 12/23/2009 :  19:46:38   [Permalink]  Show Profile  Visit marfknox's Homepage  Send marfknox an AOL message Send marfknox a Private Message  Reply with Quote
Happy HumanLight, everyone. (if you don't know what I'm talking about, http://en.wikipedia.org/wiki/Humanlight) I hope you are all having a relaxing and not too annoying holiday season. Try to stay warm, eat well, and not spend too much.

"Too much certainty and clarity could lead to cruel intolerance" -Karen Armstrong

Check out my art store: http://www.marfknox.etsy.com

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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 12/23/2009 :  20:19:34   [Permalink]  Show Profile Send HalfMooner a Private Message  Reply with Quote
Originally posted by marfknox

Happy HumanLight, everyone. (if you don't know what I'm talking about, http://en.wikipedia.org/wiki/Humanlight) I hope you are all having a relaxing and not too annoying holiday season. Try to stay warm, eat well, and not spend too much.
Same to yoou and yours, Marf! In fact, I would go further and say "Happy BioLight!"

Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
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