Physics Forums http://www.physicsforums.com Scientific physics forums for professionals and students to discuss serious issues and topics regarding physics in theory, practice, study and reality. Students can also find help for homework and career perspectives en Sat, 21 Nov 2009 03:22:54 GMT vBulletin 60 http://www.physicsforums.com/Nexus/misc/rss.jpg Physics Forums http://www.physicsforums.com Molar Specific Heat http://www.physicsforums.com/showthread.php?t=356637&goto=newpost Sat, 21 Nov 2009 03:15:11 GMT *1. The problem statement, all variables and given/known data* A certain substance has a mass per mole of 55 g/mol. When 284 J is added as heat to a 32.0 g sample of this material, its temperature... 1. The problem statement, all variables and given/known data
A certain substance has a mass per mole of 55 g/mol. When 284 J is added as heat to a 32.0 g sample of this material, its temperature rises from 22.0°C to 39.5°C

And I know that the specific heat of this substance is 507.14 J/[kg(K)]


2. Relevant equations

Q = mcLaTeX Code: \\Delta T


3. The attempt at a solution

55 g/mol * (1/32g) = 1.71875mol

284J/[(1.71875mol)/(39.5-22)] = 9.44 J/[mol(K)]

however..this is wrong and now I'm not sure where to go..help pleeeease! ]]> Introductory Physics G-reg http://www.physicsforums.com/showthread.php?t=356637 Need to find a paper http://www.physicsforums.com/showthread.php?t=356636&goto=newpost Sat, 21 Nov 2009 03:15:06 GMT I need to get this paper:

"P. Erdős and R.J. Wilson, On the chromatic index of almost all graphs, J. Comb. Theory, Ser. B 23 (1977), 255-257"

J. Comb. Theory is on ScienceDirect, but they only have the abstract online, and I can't find a hard copy of this journal in my library. Does anyone have any ideas? ]]> Academic Guidance Dragonfall http://www.physicsforums.com/showthread.php?t=356636 How to increase the abrasion resistance of rotor http://www.physicsforums.com/showthread.php?t=356635&goto=newpost Sat, 21 Nov 2009 03:14:37 GMT For Kaolin slurry filter presing we are using progressive cavity pumps.After three months of operation we found that the pumping rate is reduced a lot.Upon investigation we found taht this is because... For Kaolin slurry filter presing we are using progressive cavity pumps.After three months of operation we found that the pumping rate is reduced a lot.Upon investigation we found taht this is because of the abrasion. 150 micron Chromium coating done, still after three months ,this again failed.

The rotor is having 125mm diameter and is of 2.8m long. As the medium handled is Clay Slurry with low pH the MOC of the rotor is SS316. This rotor rotates inside a neoprene rubber stator while pumping the slurry. For the pump to develop a pressure of 10 bar the sealing between th rotor and stator is very important and the damage to the sealing area reduces the pump through put.

We are looking for a suitable method for increasing the abrasion resistance of the rotor along the sealing area.

Any suggestions?

Santhosh ]]> Mechanical Engineering Santhosh KN http://www.physicsforums.com/showthread.php?t=356635 Elastic Collision http://www.physicsforums.com/showthread.php?t=356634&goto=newpost Sat, 21 Nov 2009 03:09:17 GMT *1. The problem statement, all variables and given/known data* A 120 g ball moving to the right at 4.5 m/s catches up and collides with a 420 g ball that is moving to the right at 1.2 m/s. If... 1. The problem statement, all variables and given/known data

A 120 g ball moving to the right at 4.5 m/s catches up and collides with a 420 g ball that is moving to the right at 1.2 m/s.

If the collision is perfectly elastic, what is the speed of the 420 g ball after the collision?

2. Relevant equations

LaTeX Code: m_1v_{1i}+}m_2v_{2i} = m_1v_{1f}+m_2v_{2f}

3. The attempt at a solution

I manipulated the formula a little bit to solve for V2_f and came up with this:
LaTeX Code: (m_1v_{1i}+}m_2v_{2i} - m_1v_{1f}) / m_2

then I plugged in my numbers:
(.12*4.5 + .42*1.2 - .12*.63) / .42

simplified to this:
(.54 + .504 - .0756) / .42

and got 2.3057. Mastering physics said that is wrong however and I'm not sure what I'm doing wrong. Is the conservation of momentum the correct equation for this problem? I found the velocity of the 120 gram ball fine, which was .63 m/s, but am stuck on this one. Any help would be appreciated. ]]> Introductory Physics Atlos http://www.physicsforums.com/showthread.php?t=356634 how would you model this game? http://www.physicsforums.com/showthread.php?t=356633&goto=newpost Sat, 21 Nov 2009 03:08:53 GMT a group of 1000 players are asked to write a number greater than 0. the player who writes the lowest non-repeated number wins a prize. how would you determine which number to pick? a group of 1000 players are asked to write a number greater than 0. the player who writes the lowest non-repeated number wins a prize.

how would you determine which number to pick? ]]> Set Theory, Logic, Probability, Statistics kaleidoscope http://www.physicsforums.com/showthread.php?t=356633 How to convert and edit video/audio files for iPod http://www.physicsforums.com/showthread.php?t=356632&goto=newpost Sat, 21 Nov 2009 03:06:27 GMT This guide will so you how to convert and edit video/audio files for iPod with the best Video to iPod Converter (http://www.aidownloading.com/avcware-video-ipod-converter.html) software. *Part 1:... This guide will so you how to convert and edit video/audio files for iPod with the best Video to iPod Converter software.

Part 1: How to convert video and audio to iPod
Add files -> Select output format -> Set output folder -> Convert

Part 2: How to edit video and audio files
Trim video segment - Crop area size - Adjust video effects - Add watermark

Part 1: How to convert video and audio to iPod

Make Preparations:
Download the Video to iPod Converter.



1. Add files
Click "Add File(s)" button on the toolbar, select video or audio files you want to convert in the dialog box that opens, and add them to the file list.

2. Select output format
Choose one or more files in the file list, and open Profile drop-down list, then select an output format for selected files.

Tip: To adjust the output settings, click "Settings" button next to Profile drop-down list, and set the parameters of output format in the Advanced Profile Settings dialog box that opens.

3. Set output folder
Click "Browse" button in setting panel, select a destination folder in the dialog box that opens, and click OK.

4. Convert file
After finishing the above settings, check the files needed to convert in the file list, and click Convert Checked Item(s) button on the toolbar to start converting the files. You can view the conversion progress from the progress bar at the bottom of the window.

Part 2: How to edit video and audio files

1. Trim Video Segment
The software provides video/audio clipping function, which allows you to choose the segments you like from the source, and add them to the file list for converting.



* Select a video/audio file in the file list, click Edit button on the toolbar and choose Trim option to open Trim window.
* Click Play button to play the selected file.
* When it comes to the very start point you want, click Set Start Point button to set it as start point. And when it comes to the end point you want, click Set End Point button to set it as end point.

Tip: You can drag the slider or enter the time value you want in the Start and End textbox to adjust the position of start and end point.

2. Crop area size
Select the file you want to edit from the file list, and click Edit button on the toolbar and choose Effect option to open Effect window. Click Crop button in the left window to open crop setting panel.



* Check Enable Crop check box.
* Set Crop Area Size: Click the up and down arrow to adjust the height and width of the crop area. If you check Keep Aspect Ratio check box, the height and width will be changed proportionally.
* Set Position of Crop Area: Click the up and down arrow of Left Margin and Top Margin to adjust the left margin and top margin of the crop area.

Tips:
* Click Restore Defaults button, to restore the default settings.
* Adjust crop area manually: drag the central handle and surrounding handles in the preview window to adjust the crop area.

3. Adjust video effects
Select the file you want to edit from the file list, and click Edit button on the toolbar and choose Effect option to open Effect window, then click Effect button in the left window to go to the effect setting panel.



* Check Enable Effect check box.
* Set Brightness: click and drag brightness control slider or enter a value in the Brightness textbox to set the brightness of the video.
* Set Contrast: click and drag contrast control slider or enter a value in the Contrast textbox to set the contrast of the video.
* Set Saturation: click and drag saturation control slider or enter a value in the Saturation textbox to set the saturation of the video.
* Set Other Effects: choose an effect for the output video from the Other Effects drop down list.

Tip: Click Restore Defaults button, to restore the default settings.

4. Add watermark
Select the file you want to edit from the file list, and click Edit button on the toolbar and choose Effect option to open Effect window. Click Watermark button in the left window to open watermark setting panel, then check Enable Watermark check box. So you can add text watermark and image watermark as you want.

Done! ]]> katherine88 http://www.physicsforums.com/showthread.php?t=356632 Calgary dad wins no-homework lawsuit for his kids http://www.physicsforums.com/showthread.php?t=356631&goto=newpost Sat, 21 Nov 2009 02:44:41 GMT wouldn't it be apocalyptic if this idea catches on & spreads across the country? everybody (on this site anyway) knows this guy is mental right? he said a lot of homework is a "busy-work," especially what he said about math. according to him, once someone does the first few problems & gets the idea there's no point in doing 20 or 50 or 100 more. i was reminded of an instructor I had who brought a 3-ring binder to class one day, opened it up to show us what was inside & it was page after page of solved problems, just to show us what he had to do in order to get good at the stuff. & he said there were a dozen more binders like it in his office (which there was, in a cardboard box beneath his chalkboard). altogether they must have made a wad of paper a foot thick.... yeah... "busywork." I can imagine physics or engineering are similar.

Quote:
A Calgary family concerned about their children's homework load has signed a contract with their school to eliminate the problem altogether.

Tom and Shelli Milley have signed a formal "no homework" contract with their children's school.

"With two children in school there was just an inordinate amount of homework coming home and a lot of it was busy work," said Tom Milley.

The family has signed what is called a differentiated homework plan with their children's Catholic school. Their daughter, Brittany, and son, Spencer — now in grades five and seven — won't have to bring work home. Instead, they'll be marked only on work they do in the classroom.

The homework load kept his children from improving their weak areas, said Milley. He also questioned the value of the homework.
http://www.cbc.ca/canada/calgary/sto...-students.html ]]> General Discussion fourier jr http://www.physicsforums.com/showthread.php?t=356631 <![CDATA[The Ol' Spring and Bullet Combo]]> http://www.physicsforums.com/showthread.php?t=356630&goto=newpost Sat, 21 Nov 2009 02:42:00 GMT *1. The problem statement, all variables and given/known data* A 4.66 g bullet moving with an initial speed of vi = 410 m/s is fired into and passes through a 1.18 kg block.The block, initially at... 1. The problem statement, all variables and given/known data
A 4.66 g bullet moving with an initial speed of vi = 410 m/s is fired into and passes through a 1.18 kg block.The block, initially at rest on a frictionless horizontal surface, is connected to a spring with a spring constant of 844 N/m.
a) If the block moves x = 4.01 cm to the right after impact, calculate the speed at which the bullet emerges from the block.
b) Calculate the energy lost in the collision.

2. Relevant equations

Not entirely sure, maybe some hooke's law, maybe a little bit of momentum and KE equations.

3. The attempt at a solution

I'm not sure where to start and any hints would be much appreciated. ]]> Introductory Physics physicsbro http://www.physicsforums.com/showthread.php?t=356630 <![CDATA[l'hospitals rule]]> http://www.physicsforums.com/showthread.php?t=356629&goto=newpost Sat, 21 Nov 2009 02:36:01 GMT 1. The problem statement, all variables and given/known data
evaluate the limit
LaTeX Code: (lim.t\\rightarrow0) \\frac{e^6^t-1}{t}


2. Relevant equations
l'hospital's rule i guess


3. The attempt at a solution
With the usual approach of this rule, you are suppose to take a derivative and evaluate the derivative at that original limit. The problem is that every time I take a derivative and apply the limit I keep getting an indeterminate form. I don't know how to solve this. Can someone point me in the right direction?

Thanks ]]> hover http://www.physicsforums.com/showthread.php?t=356629 Ineffective teaching http://www.physicsforums.com/showthread.php?t=356628&goto=newpost Sat, 21 Nov 2009 02:30:18 GMT It has been a curious turn of fate and circumstance since I last posted here--instead of a mostly wannabe teacher/voluntary tutor here at PF, I became a paid, this-is-my-job kind of teacher. I took... It has been a curious turn of fate and circumstance since I last posted here--instead of a mostly wannabe teacher/voluntary tutor here at PF, I became a paid, this-is-my-job kind of teacher. I took Obama seriously, and whether too seriously, time will tell, and ended up at a cc teaching science. I've been at this a few months, gradually developing my own curriculum and materials.

Today I graded papers. A take home exam which was part of the final. I'm ready to hari-kari. Or at the very least find a more fitting profession. But I can't imagine my experience is that unique. Doubtless I have skills in need of honing, but the results were so disparate from the other exams: usu 1/2 T/F or Multiple choice and 1/2 problems, I was losing my mind. I feel like a complete and abject failure. One student of 25 scored a near perfect exam, the remainder were closer to 35-60 percent. Can i have failed this badly?

I should add the students are mostly non-traditional with a range from GED to some college/even degrees and demos are all over the map. It's a private school and an accelerated program which reduces time of study from 4 years to 22 months. Basically an operation that means well, recognizes that a lot of the material for a BS in nursing or respiratory therapy is a waste of time and focuses on clinical skills, but wishes to make a lot of money.

I'm just despondent and need ideas. I don't want to graduate a bunch of idiots, but what is up with science and math. I have college grads in my class who can't do 3/4=x/16. ]]> General Discussion denverdoc http://www.physicsforums.com/showthread.php?t=356628 Are Active Noise Control Stereo Possible? http://www.physicsforums.com/showthread.php?t=356627&goto=newpost Sat, 21 Nov 2009 02:29:45 GMT Is it possible to create an active noise control stereo that works like the headphones except they are stereos used to silence noise in a a room? Is it possible to create an active noise control stereo that works like the headphones except they are stereos used to silence noise in a a room? ]]> General Physics T.O.E Dream http://www.physicsforums.com/showthread.php?t=356627 Riding on the Brane Train… http://www.physicsforums.com/showthread.php?t=356626&goto=newpost Sat, 21 Nov 2009 02:19:59 GMT Hi, My latest animation project has shown how big (or small) subatomic particles and strings are in relationship to each other and how much empty space exists in the quantum world. Now I need to... Hi,

My latest animation project has shown how big (or small) subatomic particles and strings are in relationship to each other and how much empty space exists in the quantum world. Now I need to move on to membranes and here there’s a practical problem.

First I’ll show the ‘logical view’ the familiar brane stack… waving vertical sheets with a different world on each one. Then I’ll show the physical view of the brane… a very very thin and very very long ‘thing’ floating next to me saying that this is what the membrane really looks like. They I’ll say that everything we can see and interact with has the ends of its strings attached to the same membrane.

At this point in the animation I will single out four strings: one in my eye; one in a wall 10 feet away, one in my pool, and one in the sun. Then I’ll show the long thin brane snaking around to each one so they can connect their ends to it. Then I point out that really everything has godzillions of strings and the brane will start to snake to everyone of them basically painting everything. Then I’ll say that’s ridiculous and make all of that vanish.

Here’s where I need help. How exactly do string theorists see this working? My thought is that the ends of each string dangle into the 11th dimension and there in that dimension they find our brane. Inside the 11th dimension we see the long, thin brane and all the strings in our universe connecting to it but outside the 11th dimension we see our universe with strings were they should be and nothing snaking around to each one.

But this is just a wild guess… help me out here.

Thanks,
Rusty ]]> Beyond the Standard Model rrw4rusty http://www.physicsforums.com/showthread.php?t=356626 <![CDATA[Stress and Strain/ Hooke's Law Question]]> http://www.physicsforums.com/showthread.php?t=356623&goto=newpost Sat, 21 Nov 2009 01:52:23 GMT *1. The problem statement, all variables and given/known data* A 50 kg traffic light is suspended above an intersection by a continuous steel cable. The cable has a diameter of 1.0 cm, and the... 1. The problem statement, all variables and given/known data

A 50 kg traffic light is suspended above an intersection by a continuous steel cable. The cable has a diameter of 1.0 cm, and the light is depressed 12 degrees below the horizontal. What is the percentage increase in the length of the cable due to the mass of the traffic light?

2. Relevant equations

Stress=Force/Area
Strain=Change in length/original length
Young's elastic modulus(E)=Stress/Strain
Area = (pi) x (r^2)

E for steel is 200 x 10^9

3. The attempt at a solution

Well I found the stress and strain, but now I am lost. ]]> Introductory Physics swifel7 http://www.physicsforums.com/showthread.php?t=356623 A dumb neutrino question? http://www.physicsforums.com/showthread.php?t=356622&goto=newpost Sat, 21 Nov 2009 01:50:03 GMT I just watched the movie 2012. Now I know it's just a movie and a bit of fantasy.

What I want to know is, is there any type of radiation from the Sun that can penetrate a few miles into the Earth's crust and have some sort of effect on the rock down there. For example, can the amount of radiation in a rock be slowly increased over time only from radiation coming from the Sun? Do neutrinos become trapped in rock a few miles under ground and become detectable?

Thanks for any answers. ]]> High Energy, Nuclear, Particle Physics YADA http://www.physicsforums.com/showthread.php?t=356622 rolling a cylinder down a incline http://www.physicsforums.com/showthread.php?t=356621&goto=newpost Sat, 21 Nov 2009 01:45:01 GMT if a cylinder rolls down and incline without slipping then i decrease the coefficient of friction and it does slip a little will it have more, less, or the same kinetic energy as before I think... if a cylinder rolls down and incline without slipping

then i decrease the coefficient of friction and it does slip a little will it have more, less, or the same kinetic energy as before

I think less, my physics teacher says the same ]]> Classical Physics MatthewQueen http://www.physicsforums.com/showthread.php?t=356621