PDJ

the kind that makes his own questions rather than taking boring questions out of books that every teacher in the galaxy uses?

OK I've spent a little while looking stuff up online and in various books, and i think i might have the solution but i would still like someone to confirm this and explain it to me. This is what I've come up with. the F= kx equation, Hooke's law as it is called, applies to the force required to hold the spring compressed or stretched. That force however, is not applied over the entire distance it travels towards and beyond equilibrium... which is what the calculations are assuming? The actual force decreases as the spring approaches equilibrium, ultimately reaching zero. So the actual "average" force applied over that distance is indeed half (?) that value that my above explained calculations, which would explain why the calculation is off by a factor of two? Therefore the energy method is correct and the force method is incorrect because of the above stated reason? Confirmation and/or further explanation would be appreciated.

This is a question that was on my Physics quiz last week, kids in my class solved it in two difference ways (to be explained in a sec), which result in two different answers that are off by a factor of two. No one (including pretty much every physics teacher at my school) has found a flaw in either method... but there can't be two correct answers, right? He ended up giving credit for both answers because no one could come to a consensus about which was correct, but uhh... we still want to know which is. anyway... question: A .850 kg block is attached to a very light spring (k = 180 N/m) as shown in diagram (Diagram depicts a horizontal spring attached to a wall on one end and a block on the other, the block is also resting on a horizontal surface). When the spring block system is compressed 5 cm, and then released, it stretches out 3.2cm beyond the equilibrium position before stopping and turning back. What is the u (coefficient of friction) of the block and table. Solution 1: Potential Energies Initial potential energy of compressed spring (position 1): PE=(1/2)kx^2 = (1/2)(180N/m)(.05m)^2 = .225 J Instantaneous potential energy of spring when stretched to 3.2cm (position 2): PE=(1/2)kx^2 = (1/2)(180N/m)(.032m)^2 = .09216 J Energy lost between positions 1 and 2 is work done by friction over the 8.2cm: Wf = .225J - .09216J = .13284 J Calculate force of friction: Wf = Ff* d .13284J = Ff * .082m Ff = 1.62 N Calculate coefficient of friction: Ff = Fn * u 1.62 N = (.850 kg)(9.8 m/s^2) * u u = .194 Solution 2: Forces Force required to compress spring to 5cm: Fp = k*x = (180 N/m)(.05m) = 9 N Force required to stretch spring to 3.2cm past equilibrium: Fp = k*x = (180 N/m)(.032m) = 5.76 N Difference = force applied by friction ? Ff = 9 N - 5.76 N = 3.24 N Calculate coefficient of friction: Ff = Fn * u 3.24 N = (.850 kg)(9.8 m/s^2) * u u = .389 I do not know which of these two methods is correct (or that either is correct for that matter), but i can conclude that the coefficient of friction is indeed a constant and does not have two values, so at least one of these methods is incorrect. Can anyone provide any reason why one or both methods is wrong, and if indeed both are wrong, provide a proper method?

That's true. Just because you're a higher combat level doesn't always mean you are invinsible. People can get lucky. notice i'm not facing him? i was killing him faster with fists then he was with his weapon, i had to turn away so that he could level without me killing him :lol:

yes because you can get to device manager when the OS won't load :roll: i was trying to disable it in the bios but couldn't find the setting for it, i may look around for it later

When my brother powers on his laptop, it goes through all the various startup screens, although slower than usual. After the windows XP startup screen, the PC starts displaying the following error message continuously in an infinite loop. During the entire process the laptop is much noisier than normal, making some sort of spinning sound. error message: I assume this is something i cannot fix on my own, and that it has to be shipped off for repair... I was wondering if I could recover it by simply switching off the network card in setup but i couldn't find an option to do it. Could anyone give me any information on what that error message means?

shes on msn most of the time, not that i really talk to her, i know she was playing WOW for a while, dunno if she still is

my bank pic hasnt changed considerably in years, any old pic is probably 99% accurate :?

Its taken me just short of 2 months to get from 98 to 99 in str and def, but i finally finished. For some reason i didn't even get a message for 99 strength, but i got both 99 defense and strength in the same swing 8-) Thanks to all that came. No clue what im doing next, probably something requiring no clicking. I probably won't be leveling much either cuz im so busy with school :(

When i pked my first rune 2h (circa april 2002?), at the time worth 1.5m, roughly doubling my net worth ive made alot more than 1.5m on alot of days since then, but never increased my net worth by such a large percent in one day :P

I always thought the H/A forum was for asking advice, where as the Rate This forum was for saying "oo look at me"... that works, doesn't it? :?

what did i do to u? :?

yay yay yay, go tallest go, go go go :3>

Try not to discourage people from helping out. Helping is great, but the arrogance, of course, is unnecessary.

oo nice pic, someone told me i was here somewhere :3>

I'm sure his quoting out of context was quite intentional adam :roll:

completely disabling Norton doesn't solve it = not norton

all already checked

IE 6 i quickly installed firefox to see if it had the same problem, and it did... so i uninstalled it shortly thereafter because i don't want to leave a bunch of clutter on this pc... He is running Norton Internet Security 2004, pretty sure that there is a firewall in there somewhere because it prompted me whether or not to permit FF to access internet after I installed. edit: just quickly perused the firewall settings and couldn't find anything blatently obvious that would be causing it though. I did however learn that his antivirus hasnt been updated in 19 months and that he has NEVER had it run a full system scan--maybe I should play around with that tomorrow lol.

64MB ram running Windows XP? I didn't know that was possible lol. I vaugly remember it saying 96mb minimum on the box? lol That PC is probably atleast 7-8 years old? certainly didn't come with windows XP? You could probably pick up a PC for $300 or so that would be 10x faster than the one you have :wink:

Ok, im visiting my grandparents and I jumped on my grandfather's PC and almost every website i visit looks different. I *think* the problem is that CSS isn't working properly or not at all, but I don't know enough about that to really know for sure. Here, for example, is what the tip.it home page looks like here: Is there some setting that is off and shouldn't be? I don't know how to fix it :x edit: some other info mentioned in successive posts, but ill stick it all here: The problem occurs in both IE6 and a fresh install of Firefox (and even strips the color from Windows Live Messenger windows lol) PC is running Norton Internet Security 2004, but disabling it does not solve the issue

Done! http://i3.tinypic.com/1687ejq.jpg lol funny :) any chance u could lower the quality on it or something to get it down to the 30k tip.it sig limit? cuz otherwise its not of much use to me :? (If you can send me a pm via boards with it cuz i doubt il remember to come back here) edit: nevermind got someone else to compress it for me :3>

Render: http://www.randomfate.net/MT/media/Flyi ... onster.jpg Backround colors: blue or purple or somethin i dunno? Text: "Pker Dude Jr" in large text, "Spaghetti Monster of Doom" under it in smaller text Style: uhh whatever u like Any other crap: anything u feel like have fun

Geer, id cut you, myeslf, and milo off the list.. not saying we aren't cool... but if you include us thers 200 other people I would have included first :? Rest are certainly worthy :D