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OC
01-23-2002, 09:02 PM
On the way home I saw these skid marks on the highway about 300 feet long. You can bet THAT truck driver left a spot on the front seat!

-OC

xsiled2
01-23-2002, 09:12 PM
so you mean skid marks in both ways :hmm:

DoPeY5007
01-23-2002, 10:28 PM
Originally posted by xsiled2
so you mean skid marks in both ways :hmm: :stupid:

xsiled2
01-23-2002, 10:36 PM
you fergot ur ® dope

DoPeY5007
01-23-2002, 10:37 PM
:hmm:® :stupid:®

xsiled2
01-23-2002, 10:38 PM
:D

Pinkgirl36
01-23-2002, 10:42 PM
Originally posted by DoPeY5007
:stupid:

Originally posted by xsiled2
you fergot ur ® dope

xsiled2
01-23-2002, 10:43 PM

Pinkgirl36
01-23-2002, 10:48 PM
Originally posted by xsiled2
I dunno....I don't think I have one, sometimes I just like stating the obvious, you can just call me captain obvious :P

coleslaw
01-24-2002, 12:13 AM
Let's have FUN with some calculations here:

It was stated that the skid marks were appx. 300 ft long, which equates to about 91.44 meters.

Now, the coefficient of friction (u) for dry asphalt is generally around 0.6. Calling the stopping distance of the truck S, the equation for finding the initial velocity of the truck (in km/hr) is:

v = (255*u*S)^(1/2)

Pluggin' and chuggin', we get:

v = (255*0.6*91.44)^(1/2) = 118.28 km/hr

Converting back to MPH, we find that the truck was traveling approximately 73.5 MPH, which is WELL over the general speed limit of 55 MPH for trucks.

Now, assuming that this bastard was traveling at a speed of 73.5 MPH, we see that said moron was traveling at:

73.5 miles/hr * 5280 ft/mile * 1 hr/3600 seconds = 107.8 ft/sec.

A 300-ft stopping distance would mean that our friendly driver was skidding for:

300 ft / 88 ft/sec = 3.41 seconds.

Assuming that 3 inches of fecal matter is expelled from our friend's rear per second in his fright (this number also comes from my rear - I don't actually know the average velocity of fecal matter from someone's rear when they are scared), and assuming that said fecal matter has a diameter of 1 inch, we see that

3.41 seconds * 3 inches * pi * (0.5 inches)^2 = 8.03 cubic inches of fecal matter

have filled our truck driver's shorts.

Thanks to Thunder (http://www.gotapex.com/forums/showthread.php?s=&threadid=37918), we now know that 75% of fecal matter is actually water. Therefore, after converting cubic inches to cubic centimeters (8.03 cubic inches = 131.59 cubic centimeters), we can theorize that

131.59 cubic centimeters * 0.75 = 98.69 cubic centimeters of water exist in this stinky fecal matter.

Now, using the fact that 1 cubic centimeter of water eqauls 1 milliliter, we see that there are 98.69ml of water in the scared-fecal-matterless driver's pants.

Assume that the fecal matter does not retain its cylindrical shape in said pants, but rather, it takes a more pancake shape with a radius of 3 inches (7.62 cm), for a surface area of

pi*(7.62 cm)^2 = 182.41 square centimeters.

Assuming now that half of the 98.69ml of water is readily available to diffuse through the driver's pants due to the newly exposed surface area and its orientation, we see that the fecal water density on his seat would quickly be

49.35 ml / 182.41 cm^2 = 0.271 ml/cm^2

which, my friends, is enough to constitute a SPOT on the front seat!

Overclocked was right! :heh:

OC
01-24-2002, 12:19 AM
Originally posted by coleslaw
Let's have FUN with some calculations here:

{snip}

Overclocked was right! :heh: Well, I'm ALWAYS right - but it's nice to not have to back myownself up this time. Thx slaw!

-OC

styleee
01-24-2002, 12:22 AM
Originally posted by coleslaw
Let's have FUN with some calculations here:

It was stated that the skid marks were appx. 300 ft long, which equates to about 91.44 meters.

Now, the coefficient of friction (u) for dry asphalt is generally around 0.6. Calling the stopping distance of the truck S, the equation for finding the initial velocity of the truck (in km/hr) is:

v = (255*u*S)^(1.2)

Pluggin' and chuggin', we get:

v = (255*0.6*91.44)^(1/2) = 118.28 km/hr

Converting back to MPH, we find that the truck was traveling approximately 73.5 MPH, which is WELL over the general speed limit of 55 MPH for trucks.

Now, assuming that this bastard was traveling at a speed of 73.5 MPH, we see that said moron was traveling at:

73.5 miles/hr * 5280 ft/mile * 1 hr/3600 seconds = 107.8 ft/sec.

A 300-ft stopping distance would mean that our friendly driver was skidding for:

300 ft / 88 ft/sec = 3.41 seconds.

Assuming that 3 inches of fecal matter is expelled from our friend's rear per second in his fright (this number also comes from my rear - I don't actually know the average velocity of fecal matter from someone's rear when they are scared), and assuming that said fecal matter has a diameter of 1 inch, we see that

3.41 seconds * 3 inches * pi * (0.5 inches)^2 = 8.03 cubic inches of fecal matter

have filled our truck driver's shorts.

Thanks to Thunder (http://www.gotapex.com/forums/showthread.php?s=&threadid=37918), we now know that 75% of fecal matter is actually water. Therefore, after converting cubic inches to cubic centimeters (8.03 cubic inches = 131.59 cubic centimeters), we can theorize that

131.59 cubic centimeters * 0.75 = 98.69 cubic centimeters of water exist in this stinky fecal matter.

Now, using the fact that 1 cubic centimeter of water eqauls 1 milliliter, we see that there are 98.69ml of water in the scared-fecal-matterless driver's pants.

Assume that the fecal matter does not retain its cylindrical shape in said pants, but rather, it takes a more pancake shape with a radius of 3 inches (7.62 cm), for a surface area of

pi*(7.62 cm)^2 = 182.41 square centimeters.

Assuming now that half of the 98.69ml of water is readily available to diffuse through the driver's pants due to the newly exposed surface area and its orientation, we see that the fecal water density on his seat would quickly be

49.35 ml / 182.41 cm^2 = 0.271 ml/cm^2

which, my friends, is enough to constitute a SPOT on the front seat!

Overclocked was right! :heh:

wow, and i thought i had nothing to do.:rolleyes:

coleslaw
01-24-2002, 12:25 AM
Originally posted by styleee
wow, and i thought i had nothing to do.:rolleyes: I have plenty to do! I was just taking a break from doing some homework problems... to work on this problem :rolleyes:

Wow, I need help! :heh:

sho.gun
01-24-2002, 02:06 AM
holy buttons slaw...:eek:

eSDee
01-24-2002, 02:14 AM
Originally posted by coleslaw
Let's have FUN with some calculations here:

*regrettably snipped*

Yo slaw you are without a doubt, my favorite person on the planet for the next 5 minutes. Beautiful man, just beautiful! :D

BrewMaster
01-24-2002, 03:20 AM
Originally posted by coleslaw
\
Now, the coefficient of friction (u) for dry asphalt is generally around 0.6. Calling the stopping distance of the truck S, the equation for finding the initial velocity of the truck (in km/hr) is:

v = (255*u*S)^(1.2)

Pluggin' and chuggin', we get:

v = (255*0.6*91.44)^(1/2) = 118.28 km/hr

i've got a question abotu your calcualtions 'slaw. doesn't the force pushing down on the tires determine the amount of friction between the tires and the road? So to do this problem, you would need the mass of the truck, no? explain yourself mister! :P j/k

kimchicowboy
01-24-2002, 03:26 AM
'slaw: all i can say is what one of my roomies would say: "what the jackson?!"

and when i read the skid marks thread name, i thought of the latter meaning. i haven't been on this board for too long, but it wouldn't have surprised me to have a thread about that meaning. :P

coleslaw
01-24-2002, 03:27 AM
Originally posted by BrewMaster

i've got a question abotu your calcualtions 'slaw. doesn't the force pushing down on the tires determine the amount of friction between the tires and the road? So to do this problem, you would need the mass of the truck, no? explain yourself mister! :P j/k I knew someone was going to bring this up. The coefficient of friction actually directly counteracts any variation in the momentum of an object. In other words, one would think that a heavier object would be more difficult to stop when skidding, but actually the coefficient of friction increases the effective drag on the object, thus negating the effect of mass in the system. Here, we are talking about a sliding system, not a rolling system. The truck is skidding, thus the skidmarks.

BrewMaster
01-24-2002, 03:43 AM
Originally posted by coleslaw
but actually the coefficient of friction increases the effective drag on the object, thus negating the effect of mass in the system

if it increases the effectve drag, ie it "pushes back" stronger to countereact the mass of a larger object, how can you estimate 0.6 to be u f the dry asphalt-tire interactio? wouldn't you have to integrate over momentum? or something like that? integrate or diferentiate somehwere. basically, how would it be a constant that can be assumed since the mass does play a role but may not be in the calculation explicitly (ie, it might be momentum that we deal with, which is a product of the mass as I'm sure you alraedy know).

i'm not trying to be an ass or anything, i actually think this discussion is quite interesting actually. just asking...

coleslaw
01-24-2002, 04:03 AM
Basically, from a free-body-diagram perspective, mass is a factor in the momentum in the x direction while it is also a factor in determining the drag in the -x direction.

*------------*
| |
| |
u S <--------*-----------> m v
| | |
| | |
*-----|------*
|
v
m g

When you take the dot product of the momentum and the weight vectors, you will notice that their angle of separation is 90 degrees. Thus, when you dot m v with m g, a cosine term enters. The cosine of a 90 degree angle is 0, therefore, the mass is essentially dropped out of this system. What's left is v, u, and S.

Oh, and 0.6 was just a value that I pulled from a coefficient chart. That value should be fairly constant for all objects on dry asphalt.

BrewMaster
01-24-2002, 05:06 AM
thanks for the explanation 'slaw. i'm not sure i fully get it, but whatever. you brought back some old school memories of freshman physics by talking about dot products. hehe.

Kim
01-24-2002, 09:26 AM
Now I remember why I never went to college. Thanks for reminding me! :D

whitak24
01-24-2002, 10:21 AM
coleslaw
this is seriously one of the most hilarious threads i have ever seen on here. if there is a got|apex? hall of fame, this thread should be entered there.
good work.....damn i'm glad i escaped with only a year of high school physics :D

Thunder
01-24-2002, 01:49 PM
nerds!!!!!...all this to say he left a spot in the front seat!!!

-slaw...i think the homeworks is getting to you:D

Markel
01-24-2002, 01:55 PM
I think 'slaw has a definite future as an engineer. :P

Grimm
01-24-2002, 03:33 PM
Originally posted by coleslaw
Basically, from a free-body-diagram perspective, mass is a factor in the momentum in the x direction while it is also a factor in determining the drag in the -x direction.

*------------*
| |
| |
u S <--------*-----------> m v
| | |
| | |
*-----|------*
|
v
m g

When you take the dot product of the momentum and the weight vectors, you will notice that their angle of separation is 90 degrees. Thus, when you dot m v with m g, a cosine term enters. The cosine of a 90 degree angle is 0, therefore, the mass is essentially dropped out of this system. What's left is v, u, and S.

Oh, and 0.6 was just a value that I pulled from a coefficient chart. That value should be fairly constant for all objects on dry asphalt.
Translation:
The inertia of the mass roughly equal to the added friction caused by the weight of the mass.

Or:

It don't matter none (for you rednecks).

styleee
01-24-2002, 06:03 PM
now i know who to ask for help this summer when i take the second half of general physics.

considering that i took the first half 7 years ago, i have a pretty good feeling i'm going to need a bit of help to brush up!

BrewMaster
01-24-2002, 06:21 PM
Originally posted by Grimm
It don't matter none (for you rednecks).

this is what i love about G|A, no one gets left out...

whitak24
01-24-2002, 06:27 PM
Originally posted by BrewMaster

this is what i love about G|A, no one gets left out...
why, did you feel like that remark was just for you, brew? :P

BrewMaster
01-24-2002, 06:37 PM
Originally posted by whitak24

why, did you feel like that remark was just for you, brew? :P

i reckon you was there-a-makin'-a-funna me, hu?

coleslaw
01-24-2002, 10:44 PM
Originally posted by Markel
I think 'slaw has a definite future as an engineer. Future? Nah, I'm already there! :P

01-25-2002, 02:13 AM
Originally posted by Pinkgirl36

I dunno....I don't think I have one, sometimes I just like stating the obvious, you can just call me captain obvious :P

You would be wise to watch out, Pinkgirl36, ranks like Captian Obvious have been known to stick! ;)

Oh, btw, coleslaw, that has to be the most interesting physics lesson I think I've ever had the privilege of reading! :P

Windsor
01-25-2002, 02:28 AM
Captain Obvious to the rescue!!

Anyone here read Non-Sequitor? Great cartoon.

johnnymk
01-25-2002, 04:52 PM
Methinks that coleslaw is currently a Maniacal Engineer. That was one of the funniest posts I have seen in a long time.
And to think that an engineer could have a sense of humor!

coleslaw
01-25-2002, 06:05 PM
Originally posted by johnnymk
Methinks that coleslaw is currently a Maniacal Engineer. That was one of the funniest posts I have seen in a long time.
And to think that an engineer could have a sense of humor! Do you mean mechanical engineer? or maniac-al engineer?

Either way, I'm an electrical engineer. I actually despise mechanics! :P

Windsor
01-25-2002, 06:13 PM
Originally posted by coleslaw
Do you mean mechanical engineer? or maniac-al engineer?

Either way, I'm an electrical engineer. I actually despise mechanics! :P

I think he means Maniacal as in :borg: :woo: :johnwoo2: :mad3: this Maniacal.

johnnymk
01-25-2002, 06:31 PM
Maniacal... Yes.

I have been an engineer for a long time, and to find one with a sense of humor is very rare indeed.:P

El Scorcho
01-25-2002, 07:43 PM
Originally posted by coleslaw
Let's have FUN with some calculations here:

It was stated that the skid marks were appx. 300 ft long, which equates to about 91.44 meters.

Now, the coefficient of friction (u) for dry asphalt is generally around 0.6. Calling the stopping distance of the truck S, the equation for finding the initial velocity of the truck (in km/hr) is:

v = (255*u*S)^(1/2)

Pluggin' and chuggin', we get:

v = (255*0.6*91.44)^(1/2) = 118.28 km/hr

Converting back to MPH, we find that the truck was traveling approximately 73.5 MPH, which is WELL over the general speed limit of 55 MPH for trucks.

Now, assuming that this bastard was traveling at a speed of 73.5 MPH, we see that said moron was traveling at:

73.5 miles/hr * 5280 ft/mile * 1 hr/3600 seconds = 107.8 ft/sec.

A 300-ft stopping distance would mean that our friendly driver was skidding for:

300 ft / 88 ft/sec = 3.41 seconds.

Assuming that 3 inches of fecal matter is expelled from our friend's rear per second in his fright (this number also comes from my rear - I don't actually know the average velocity of fecal matter from someone's rear when they are scared), and assuming that said fecal matter has a diameter of 1 inch, we see that

3.41 seconds * 3 inches * pi * (0.5 inches)^2 = 8.03 cubic inches of fecal matter

have filled our truck driver's shorts.

Thanks to Thunder (http://www.gotapex.com/forums/showthread.php?s=&threadid=37918), we now know that 75% of fecal matter is actually water. Therefore, after converting cubic inches to cubic centimeters (8.03 cubic inches = 131.59 cubic centimeters), we can theorize that

131.59 cubic centimeters * 0.75 = 98.69 cubic centimeters of water exist in this stinky fecal matter.

Now, using the fact that 1 cubic centimeter of water eqauls 1 milliliter, we see that there are 98.69ml of water in the scared-fecal-matterless driver's pants.

Assume that the fecal matter does not retain its cylindrical shape in said pants, but rather, it takes a more pancake shape with a radius of 3 inches (7.62 cm), for a surface area of

pi*(7.62 cm)^2 = 182.41 square centimeters.

Assuming now that half of the 98.69ml of water is readily available to diffuse through the driver's pants due to the newly exposed surface area and its orientation, we see that the fecal water density on his seat would quickly be

49.35 ml / 182.41 cm^2 = 0.271 ml/cm^2

which, my friends, is enough to constitute a SPOT on the front seat!

Overclocked was right! :heh:

thats all fine and dandy but you forgot a few things...

(1)wind factor (2) condition of tires (3) condition of street (4)condition of truck driver's underpants (considering he was wearing them, and if he wasnt i dont even want to start on the levi/fecal/skidmark theory) and (5) that most truck drivers are NOT normal people and that they ACTUALLY have 45% water, 35% roadkill, 5% tobacco, and 15% U.F.M.C. (unidentified fecal matter content)

So perhaps you should take this factors into consideration next time!

:D :) ;) :P