Some random questions on stuff I've seen on tv.

[Killer Bees]

To answer your counterfeiting question, click the link below.
It's quite informative!   

http://money.howstuffworks.com/counterfeit.htm

One of the main reasons it's so hard to get away with counterfeiting is because of the type of paper used.
Rag paper, which is controlled by the U.S. government and not available to the public, is what gives our currency that distinctive feel.  You don't get that with other types of paper.

Our notes are all plastic and I understand it's pretty much impossible to counterfeit those.  It's a good idea.  Makes them last longer.  But they can tend to stick together if you get brand new ones from the ATMs.

[Ash]

I have some Aussie money I brought back from Oz.
It was weird the first time I saw it.  It's nothing like U.S. currency.
Your bills are all multi-colored and the larger the denomination, the larger the physical size of the bill.

I found that it was cheaper to convert my US dollars into Aussie dollars before I went and spent a month in Adelaide.

And Australia is a very change-heavy country.
Lots of one dollar, two dollar and 50 cent coins.  (they haven't taken off here in the US like they have there)
I managed to get my hands on almost all of those recent commemorative 50 cent pieces.
(the ones with the special designs on the back)
There was so much change in my pockets the entire time I was there, I needed a belt to keep my shorts up!    

[Killer Bees]

I have some Aussie money I brought back from Oz.
It was weird the first time I saw it.  It's nothing like U.S. currency.
Your bills are all multi-colored and the larger the denomination, the larger the physical size of the bill.

I found that it was cheaper to convert my US dollars into Aussie dollars before I went and spent a month in Adelaide.

And Australia is a very change-heavy country.
Lots of one dollar, two dollar and 50 cent coins.  (they haven't taken off here in the US like they have there)
I managed to get my hands on almost all of those recent commemorative 50 cent pieces.
(the ones with the special designs on the back)
There was so much change in my pockets the entire time I was there, I needed a belt to keep my shorts up!    

I hear that.  I love getting $1 and $2 coins.  When you put them in a jar, they look like gold dubloons and you can pretend you'e actually rich!    I love the greenish colour of the $100 notes.  Alas, I never seem to get any of them  *lol*

I had trouble with US currency when I was there.  I really had to look hard at which note I was handing over. 

I'm sorry you had to go to Adelaide.  I hope it won't stop you from visiting our country again in the future

[zbranigan]

I had trouble with US currency when I was there.  I really had to look hard at which note I was handing over. 

it must suck for blind people (not you ) mistaking a $100 for a $1 because its the same size

[Killer Bees]

I had trouble with US currency when I was there.  I really had to look hard at which note I was handing over. 

it must suck for blind people (not you ) mistaking a $100 for a $1 because its the same size

It sure did.  Many times I thought I had more money in my purse than I actually did.  At least at home, I can just look at all the pretty colours and know exactly how much cash I have  *lol*

But I loved the US. If I could get a green card, I absolutely would move there. 

[BixDugan]

Question 1 - Yes

Isn't there a little more to it than simply trying to make the money look 'less new'?  Real money has fiber threads 'woven' into the paper.  Some counterfeiters used to (it's not really all that effective) wash the money with old rags to 'embed' the paper with lint to reproduce this.

It's better to have the threads in the paper before it's printed.

Question 3 -- C4 and the like need a concussion to detonate. If you was to roll C4 into a little ball and shot it with a sling shot it would explode upon contact. The detonators only provide the concussion blast to detonate it. The electrical is only needed for the detonators.

Are you sure about that slingshot part?  There's a BIG difference between the shock generated by a cap (at least tens of kilobar moving at around 6000 meters per second) and a ball from a slingshot.

Pulling out my trusty copy of Mader's Numerical Modeling of Explosives and Propellants, in Chapter 4 we find a section titled "Projectile Initiation of Explosives."  The key parameter found in projectile initiation is V^2*d, where V is the velocity of the projectile and d is it's diameter.  If the V^2*d value for a projectile is smaller than the high explosives critial value, no detonation will occur.

I don't have numerical data for C4, but I do have for a 60-40 mix of RDX (the hi-ex component of C4) and TNT.  The critical value for this explosive is V^2*d = 5.8 mm^3/us^2.  This translates to 761 m/s for a 1 cm projectile hitting the surface of the explosive, or about 2200 fps.  For other hi-ex mixtures, such as Composition B3, the critical values are even higher.

You getting 2200 fps out of your slingshot?

Now, if you have eyeballs-on experience to the contrary, I'd love to hear about it - computational modeling of explosives, detonation initiation and the deflagration-detonation transfer is the kind of research that I do, so your observations would be relevant.

In practice, the real reason more than one detonator is used is reliability.  You also get some charge directionality from where the initiator is placed, so sometimes you can "focus" the blast a little bit with detonator placement.

Note to self:
Never mess with Ulthar.


I though you could home brew Napalm with Gasoline and styrofoam.

[ulthar]

But I loved the US. If I could get a green card, I absolutely would move there. 

That's funny!  We are talking about moving to Australia for a year.  One of the few jobs Americans can get a temp visa for down there is teaching science, and guess what I do.   

I'd LOVE to visit for a year....though I sometimes wonder about moving to NZ permanently.

[Killer Bees]

But I loved the US. If I could get a green card, I absolutely would move there. 

That's funny!  We are talking about moving to Australia for a year.  One of the few jobs Americans can get a temp visa for down there is teaching science, and guess what I do.   

I'd LOVE to visit for a year....though I sometimes wonder about moving to NZ permanently.

NZ is beautiful.  It reminds me of Canada a lot and I loved it there.  Plus if you're used to snowy winters and mild summers, it's a great place.  But things are pretty expensive, that's the only drawback.  And they all have funny accents  *lol*

We'd love to have you in Aus, Ulthar, especially if your job is something interesting and worthwhile like teaching science.

[Ash]

I'm sorry you had to go to Adelaide.  I hope it won't stop you from visiting our country again in the future

I hear that all the time when I tell people I went there!
What do people have against Adelaide?
I thought it was awesome and had a blast.
I guess it all depends on who you're there with.
Luckily, I was in good company.   

[Justy]

As far as bullets travelling through water, I saw that Mythbusters episode and if memory serves, a 9 mm handgun bullet would travel about nine feet through water and still be fairly deadly.  As they increased the velocity of the firearm, the bullets became less and less effective.  The friction of the water would tear the bullet apart before it travelled very far.  At the end they fired a 50 cal rifle into a swimming pool, and despite the enormous splash, the bullet didn't even hit a target three feet under water.  I think that was actually an armor piercing round, but I can't say for sure. 

LoL... This discussion is running parallell to the current book I'm reading The Butlerian Jihad its one of the Dune prequels. In it the scientist Tio Holtzman just created the personal body shields. If you've read the later Dune novels or saw the movies you know the shields that I am talking about. They may not be exactly the same but the first models were just created. Anyways, one of the flaws of the shields is that they are great for stopping high velocity attacks, projectiles, concussion, explosions, etc. The higher the velocity the better they work. However, they are ineffective against slow moving objects. The principle must be the same. I guess as the velocity of the object increases the greater the resistance of the water because the molecules are not being pushed away fast enough. A slow moving object just lazily makes it way through the liquid pushing the molecules away as it encounters them.

[AndyC]

I hear that.  I love getting $1 and $2 coins.  When you put them in a jar, they look like gold dubloons and you can pretend you'e actually rich!    I love the greenish colour of the $100 notes.  Alas, I never seem to get any of them  *lol*

I wasn't too sure about $1 and $2 coins when they introduced them in Canada. More bulky change in your pocket.

But I quickly came to love the "Loonie" and "Tooney" because I could have an empty wallet, feel broke, then reach into my pocket full of change and find a few dollars without even having to do much counting. It's nice when you feel like buying a coffee to find more cash than you thought you had on you.

American money - definitely confusing when you're used to differentiating bills by colour.

[Killer Bees]

I'm sorry you had to go to Adelaide.  I hope it won't stop you from visiting our country again in the future

I hear that all the time when I tell people I went there!
What do people have against Adelaide?
I thought it was awesome and had a blast.
I guess it all depends on who you're there with.
Luckily, I was in good company.   

It's just a joke here.  We always need someone to pick on!  Basically Adelaide is perceived as boring.  We call it the city of churches for obvious reasons.  But anyone who voluntarily lives in Adelaide is seen as slow and dim witted  *lol*

Like people who live in Tasmania are perceived as being inbred because it's mainly forests and mountains and uninhabited places and you can easily get lost.  So there's a lot of "your parents must have been brother and sister" type humour.  It's our version of having rednecks.

It's all just good fun.  I've never been to Tassie or Adelaide, but I'd really like to visit.  I'm sure I'd love it there as well.  Word of advice though, don't visit Adelaide in our summer (Dec - Feb).  You'll be regularly hit with scorching temps.  It's not unheard of for Adelaide to have constant temps in summer between 95F and 113F (35C - 45C).  Even here in Brisbane where it's sub tropical and the summers are hot and humid we say, "wow, that's hot weather!"

[Killer Bees]

I hear that.  I love getting $1 and $2 coins.  When you put them in a jar, they look like gold dubloons and you can pretend you'e actually rich!    I love the greenish colour of the $100 notes.  Alas, I never seem to get any of them  *lol*

I wasn't too sure about $1 and $2 coins when they introduced them in Canada. More bulky change in your pocket.

But I quickly came to love the "Loonie" and "Tooney" because I could have an empty wallet, feel broke, then reach into my pocket full of change and find a few dollars without even having to do much counting. It's nice when you feel like buying a coffee to find more cash than you thought you had on you.

American money - definitely confusing when you're used to differentiating bills by colour.

I loved the loonie and the toonie when I was in Canada.  Just the name cracked me up!  And the fact that one of them had a hole in it and was dual coloured.  You gotta love multi coloured holey coins as currency.   

[AndyC]

Two metals in one coin is pretty cool. When they came out, I remember a few people were trying to break the centre loose by alternating heat and cold. That didn't last long. They are quite durable.

The biggest complaint I heard about the toonie was from friends who used to frequent strip bars. Suddenly, the smallest bill you could stuff between a stripper's boobs was a five. That was back when most of my friends got married, and these guys would hoard every $2 bill they got their hands on for bachelor parties.