1

Just Chat! / New Forum theme

« on: 16/04/2014 11:55:12 »

I hope you like it, I think it is cleaner than the old one, and fits with the rest of the site better.
If there are any problems can you put them in here
  cheers
    Dave

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Physics, Astronomy & Cosmology / Re: calculate the instantaneous velocity

« on: 16/04/2014 09:21:04 »

The energy in a spring which follows Hooke's law is where f is the force at maximum extension, the is essentially averaging the force.

You have been given the average force, so the energy in the spring is going to be

Does that produce the speed you were expecting?

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Radio Show & Podcast Feedback / Re: Is charging from the mains and USB the same?

« on: 09/04/2014 12:45:04 »

Both a mains charger and a usb socket will give your phone 5V depending on the specs of both the current they provide will be different so the rate of charging can be different, between chargers and USB sockets.

More modern USB sockets will give more current, but some older ones particularly on laptops don't give much

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Question of the Week / Re: Why can I squirt a jet of saliva?

« on: 12/11/2013 11:58:47 »

I sometimes get a similar effect when yawning, normally as I am starting to salivate - it rarely works twice. I guess because my salivary glands in the sides of my mouth get over full, and the yawning stretches and compresses them, squirting the saliva out.

5

Science Experiments / Rollin pin

« on: 29/10/2013 10:24:43 »

As a roller for moving things around
Could carve it into a very small totem pole
Wheels for a very rubbish go kart
A lever for opening things
Screw it onto a coffee table to replace a leg
Crude club
The axle could be used as a poker
Firewood
A very rubbish mallet
A guide for a sliding door
Two could be jammed into a surface to build a roller fairlead for a large rope
Pulley
etc. etc.

I am not sure if that makes me wierd - I did have a thump on the head about 10 years ago...

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Technology / Re: Why is there not no institution on earth preventing loss of scientific knowledge

« on: 23/04/2013 17:03:56 »

There are things like archive.org and the big libraries are doing it to some extent - I think the British Library just got some responsibilities in that direction. But storing large quantities of digital data for a long time is an unsolved problem.
http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/20130321/

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New Theories / Re: Ben Fraklin, magnets and attractive/repulsive forces

« on: 21/08/2012 15:50:59 »

I think that magnetoforming of aluminium is probably done with a rapidly changing magnetic field, not a static one. This induces eddy currents in the aluminium, turning it into an electromagnet, and it is these currents which are repelled by the coils inside, and push the aluminium away.

This is very standard electromagnetism.

The flow of magnetism you are talking about is normally called magnetic flux. It isn't a real thing, it is just a way of interpreting the equations of electromagnetism in terms of something which the human mind can get a handle on.

Arguably positive and negative were labelled the wrong way it might make more sense for electrons to be positive, but that is the way the convention was set up, so we are stuck with it.

Possibly some of the reason that WWII era welders were not marked +ve and -ve was that they were probably running AC not DC, in which case there isn't a +ve and -ve electrode, just live and neutral, or whatever you want to call that.

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Science Experiments / Re: Which boils first?

« on: 21/08/2012 14:36:40 »

Yes there will be an effect where you can get a single full cup at the centre of the microwave, where the microwaves are normally more intense, where as the 2 cups will be circling around it

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Science Experiments / Re: Could someone explain the can crushing experiment?

« on: 21/08/2012 14:35:11 »

The reduction in pressure, so volume is to do with a phase change - going from gas to liquid. Ideal gasses don't liquify so their laws won't help you.  There are lots of equations to do with phase changes, but they are more complex, and involve more experimentally determined constants than I think you are looking for.

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Just Chat! / Slight change to the forum

« on: 14/08/2012 14:28:30 »

If you hadn't noticed, I have slightly changed the images to the left of topic titles in the forum, they are now purple if you haven't read them, yellow if you have, and open if you have posted in them (how it used to work before christmas)

Hopefully that is helpful and not too ugly.
  Dave

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Physics, Astronomy & Cosmology / Re: How does ironing work?

« on: 14/08/2012 14:03:34 »

The other reason for ironing needing water in cotton is that cotton is made of cellulose which is long chains of sugar, these are covered with OH groups - almost a water molecule. The O is slightly negative and the H positive. This means that when it is dry they form bonds between molecules locking them together.

The OH groups can also bond to water, so if you make the cotton hot and wet instead of bonding between molecules you bond to water, lubricating the molecules and allowing them to reconfigure. If this is done while being squashed, and then dried out the molecules will then lock into a flat configuration.

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New Theories / Re: Einstein's wrong assertions: split from Do the mechanism in clocks really run slow?

« on: 13/08/2012 15:47:46 »

I don't think that Einstein proposed a mechanism for the time dilation - he just produced a set of equations which neatly combined electromagnetism into one force, and have since been shown to work again and again.

Whether equations need mechanisms on a fundamental level is really quite deep philosophy, and every mechanism will end up with 'because that's how the universe is' after digging down through enough layers, and it is not obvious to me that is a great problem, unless you can find evidence for another deeper layer of mechanism underneath it.

A lot of problems with special relativity stem from trying to apply it to situations which it wasn't designed for. It only works for inertial reference frames - moving at a constant velocity, this means that the twin paradox can't be solved using it - moving two twins apart and then moving them back again involves accelerations, which are not included in special relativity.

To deal with these you need General Relativity, which is 'difficult', seems to involve a 1000 page A4 text book which sits 'waiting for a couple of years' to read on most academic physicist's shelves and which I avoided at undergrad. But I am assured by people who would love to prove it wrong (Nobel prize anyone) that it fixes the problems everyone has with special relativity.

I am not saying that there can't be problems with General relativity (though it has passed all the tests it has had so far) but that to propose them you need to understand it at lot better than I do. Happy reading....

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Question of the Week / Re: QotW - 08.01.06 - Why do wires tangle?

« on: 08/05/2012 15:09:09 »

Some of the problem is probably to do with twists, but less when they are made and moe how they are used, coiling puts twist into a cable, but rolling doesn't, so if you roll and then uncoil, or coil and then unroll you will change the number of twists.

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Physics, Astronomy & Cosmology / Re: how does this open wine bottle with shoe trick work?

« on: 08/05/2012 11:47:06 »

We did this on the show and found out it was due to cavitation:
http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/opening-a-bottle-of-wine-without-a-corkscrew/

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Question of the Week / Re: QotW - 09.04.26 - Do magnets remove lime scale from water pipes?

« on: 11/04/2012 12:20:52 »

Nothing wrong with using a magnet to collect ferrous metals fragments and associated sludge, that would damage a pump, or gum up your system, that makes sense... this is very different from using it to 'soften water'.

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Physics, Astronomy & Cosmology / Re: How much hydrogen does Earth lose annually?

« on: 03/02/2012 00:38:22 »

The NASA reference is here:

http://www.nasa.gov/vision/earth/environment/earth_energy.html
http://www.sciencemag.org/content/308/5727/1431

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Just Chat! / Re: sorry for teh problems

« on: 18/12/2011 15:14:58 »

You mean the greatest comments I ever made are gone, as if they never were made...........

All I can say, is sorry... []

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Just Chat! / Re: sorry for teh problems

« on: 18/12/2011 15:11:17 »

Dave, are you guys planning on changing the style of the TNS forum? Or is this new layout only momentary until you've got it back to before?

As for the rest you've done.
Great work..

Sorry yes, I wanted to upgrade the forum to a newer version for security reasons, and that came with a new style as getting the exact same old one back would have been even more work than just getting most of the functionality,

 the old server crash meant moving it onto the newer forum software in a horrible rush and I didn't have time to warn you. So there will be some teething problems.

On the up side you can now use tex tags if you know any latex to make pretty equations.

is made by

Code: [Select]

[tex]\frac{\alpha \beta}{\delta x}[/tex]
And the diagram drawing feature should work a lot better. as long as you are using firefox, chrome or a recent version of ie
[diagram=657_0]


I think I have fixed the personal messages formatting, and recent topics is almost working.

If anything grates tell me and I will see what I can do.

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Just Chat! / Re: sorry for the problems

« on: 18/12/2011 14:32:12 »

There are a few teething problems,
the personal messages interface has issues with formatting.

which I am working on. If you notice any please tell me and I will see what I can do.

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Just Chat! / sorry for teh problems

« on: 18/12/2011 02:07:44 »

Due to sleep deprivation, and some odd commands I managed to delete yesterdays data, but have restored the previous two weeks, really sorry.
   Dave

Should be the end of the problems now... plus hopefully this server is faster