-  [WT]  [PS]  [Home] [Manage]

  1.   (new thread)
  2.   Help
  3. (for post and file deletion)
/sci/ - Science, Technology, Engineering, and Mathematics

Join us in IRC!

•This is not /b/ or /halp/. Tech support has its own board.
•If you are not contributing directly to a thread, sage your post.
•Keep the flaming at a minimum.
•Tripcodes⁄Namefags are not only tolerated here, they are encouraged.
•We are here to discuss sci-tech, not pseudoscience. Do not post off-topic.

•♥ Integris


  • Supported file types are: GIF, JPG, PNG, WEBM
  • Maximum file size allowed is 5120 KB.
  • Images greater than 200x200 pixels will be thumbnailed.
  • Currently 424 unique user posts. View catalog

  • Blotter updated: 2011-01-12 Show/Hide Show All

There's a new /777/ up, it's /gardening/ Check it out. Suggest new /777/s here.

Movies & TV 24/7 via Channel7: Web Player, .m3u file. Music via Radio7: Web Player, .m3u file.

WebM is now available sitewide! Please check this thread for more info.

how to make airplane Anonymous 15/01/04(Sun)17:37 No. 16019 ID: 61d208 [Reply]
16019

File 142038945866.jpg - (548.56KB , 1280x720 , F24F35.jpg )

http://youtu.be/XjEO8NqgAKk




Cryptoforums.net Technology Forum Cryptoforums.net Technology Forum 14/05/13(Tue)10:25 No. 15656 ID: 288b60 [Reply]
15656

File 139996955137.png - (8.43KB , 82x77 , CF-logo.png )

Hello chans of the internet. We at https://cryptoforums.net have created a MyBB forum dedicated to the discussion of things like Bitcoin, Privacy, Security, Cryptography, GNU/Linux, Philosophy, Politics, Freedom, Cryptocurrency, Hacking and many other general subjects. We are currently in our early stages and we want to invite more members. If you like any of those subjects you should come check us out! We also respect anyone's opinion even if negative so give us all your positive/negative support/criticism!


7 posts omitted. Click Reply to view.
>>
Anonymous 14/08/11(Mon)18:38 No. 15815 ID: d9f5aa

>>199869
the joke's getting old, shillfag.

OP your forum would be a lot more appealing if it didn't require an email.
trashmail makes it easy but waiting for the email to arrive is a fucking dealbraker.
I'd probably rather enter a fucking google recaptcha and have my everchanging dynamic IP logged by some useless waste-of-money agency than wait for a shitty activation mail (and possibly still get logged if my ISP or trashmail provider is sharing data as much as google does).


>>
Anonymous 14/08/11(Mon)18:39 No. 15816 ID: d9f5aa

>>15662, not 199869 obv.


>>
Registration requires captcha, but none displayed for me Anonymous 15/01/02(Fri)05:55 No. 16015 ID: 226b1d

I've tried to register on cryptoforums three times tonight, using Opera, FireFox, and IE. In all three browsers, I agree to the terms, populate the fields, and submit the form, to be greeted with:


Please correct the following errors before continuing:
•The image verification code that you entered was incorrect. Please enter the code exactly how it appears in the image.

There is no captcha image to enter. There's a question to answer, which I answered correctly each time.

Is the new user registration broken, or am I the only one having this issue?

Also, your Contact Us mailto link is broken. It contains no email address. Ergo, I could find no way to reach a site administrator, hence the post here.

Thanks.




Anonymous 13/07/18(Thu)15:31 No. 15206 ID: 9083c1 [Reply]
15206

File 137415428455.jpg - (94.22KB , 640x569 , turkey_roast.jpg )

I might sound like an idiot for asking this, but can somebody explain the science behind the following:

When you're grilling two steaks over a flame, it takes the same amount of time, whether it's just one or two steaks.

When you're roasting two turkeys inside an oven, it usually takes 1.5 to 1.8 times longer than when there's just one turkey inside.

Why doesn't it take the same amount of time as it does when grilling two steaks over a flame?

Why am I an idiot for not understanding this?


2 posts omitted. Click Reply to view.
>>
CandleJack 13/07/23(Tue)22:45 No. 15220 ID: 2f260d

>>15219

Ovens are not perfectly efficient. With the one turkey, say 50% of the energy goes toward heating it, while the remainder heats the air or escapes outside. With two turkeys, 75% of the heat goes to them, while the rest heats the air (which there is less of because the oven is more full) or escapes.


Have you heard how a full refrigerator is more efficient than an empty one? That's because it takes more energy to heat or cool air (and maintain it) than it does to heat or cool an object. It's just like that, but in reverse. Because there is less air in the oven, it doesn't waste energy heating that air; the conserved energy goes into heating the other turkey.


>>
Anonymous 13/07/24(Wed)01:59 No. 15221 ID: 9083c1

>>15220
Now I get it, thanks a lot!


>>
Anonymous 14/12/30(Tue)20:13 No. 16012 ID: a607c9

>>15220

Thats incorrect. It is a common misunderstanding that air needs more energy to cool down in a fridge than solid or liquid mass(like bottles full of water) does.
While it is true that a full fridge uses less energy than a empty one, that is only the case if you leave the solid mass inside. Air has a thermal capacity of roughly 1 J/gK (Joule per gram and Kelvin ). The thermal capacity of Water is very roughly 4 times higher. This means you would need 4 times the energy to cool down (or heat up) 1 kg of Water than 1 kg of air. A fridge is typically less than 200 liters big inside, which is 0,25 Kg of air. If you put something in your fridge which is at least 0,065 kg (or 65 g) heavy and mostly made of water, it will take more energy to cool down than if all the air inside the fridge would have changed.

So why is it still more efficient to have a full fridge than an empty one?
When you open the fridge there is normally no liquid or solid mass leaking. However the cold air is escaping even if you don't want cold air in your kitchen. Thus the air loss is energy loss. If you have a full fridge there is less air in it and therefore less air can escape.
Top-opening-freezers are more efficient because of that. Cold air is more dense (heavier) than warm air. The cold air stays in the top-opening-freezer while it floats out of a front-opening-freezer.




World's Simplest Electric Train Jeson 14/12/23(Tue)20:30 No. 16007 ID: 3791e5 [Reply]
16007

File 141936303681.png - (512.38KB , 1459x468 , baterija.png )

The trick in the video is that the magnets are made of a conducting material and they connect the battery terminals to the copper wire, so the battery, magnets and copper wire make a circuit that generates a magnet field just in the vicinity of the battery. The geometry means the two magnets are automatically at the ends of the generated magnetic field, where the field is divergent, so a force is exerted on the magnets.

The magnets have been carefully aligned so the force on both magnets points in the same direction, and the result is that the magnets and battery move. But as they move, the magnetic field moves with them and you get a constant motion.

If you flipped round the two magnets at the ends of the battery the battery and magnets would move in the reverse direction. If you flipped only one magnet the two magnets would then be pulling/pushing in opposite directions and the battery wouldn't move.

What you need:
1. Neodyum magnets
2. Dry cell battery
3. Copper wire


>>
World's Simplest Electric Train Jeson 14/12/23(Tue)20:38 No. 16008 ID: 3791e5

Video:
https://www.youtube.com/watch?v=aTnK1gl_yag




Delete post []
Password  
Report post
Reason