insane_alien

you brought it up.

bellbottom, we have given you experiments you can try yourself in your own home that show that there is friction between metals. you are the foolish one if you can not see what is right infront of your face. have you even seen a close up of a metal surface? even if it looks mirror smooth it has lots of ridges on it. these cause the friction between metals. no amount of name calling will change the fact that there is friction between metals. evidently not. a little humility would be good for you.

i comes from definitions one and two there. empirical formulae were first derived by decomposing the molecules and getting the ratios of the elements present in the compound. it gives no hint of structure or reaction chemistry.

no, the vibrations are far to small and the frequencies too high even at very low temperatures.

imp, area doesn't come into it. it cancels out because the less area you have then the more pressure. the areas cancel and you are left with the normal force, and, assuming the mass doesn't change considerably, this is a constant.

hydrinos do not and cannot exist. it's a scam.

Thanks ecoli, didn't know about that. Added.

The SFN chat room is a great place to get quick answers for questions. Usually there are several of us in the chat room at any given time. This is an under used feature of these boards and we would like it if some of you new users gave it a shot. There are three ways to get chatting to us, the simple(but not very good way), the slightly more complicated way(but useful and more feature rich way) and the way for those who are blocked by schools or work. Seeing as most of you will just be wanting to ask a quick question and probably not be on that often the simple way will be the best for you. 1/ The Simple Way Click "Chat" on the bar at the top of this page (the one with "Forums" and "Blogs"). That should be you set. You can also bookmark http://chat.scienceforums.net/?channels=sfn&prompt=1 for use whenever you want it. 2/ The better way For those of you who find yourself using the chatroom often then this will be the better choice for you. It's not too difficult and you only have to do it once. This way uses the 'X-Chat' program. To get the X-chat program, Click here. (Windows only) Linux users should check their distributions repositories. Mac users can get it here. Once this is installed there are a few bits of configuration to go through. When you first open this program you will see a screen similar to this: (without the SFN and Ubuntu bits along with the user information i added those later, you can ignore the rest of the networks) First click fill out your user information. Nickname is what you'll appear to everybody as. User name and Real name do not have to be your proper name but the fields must be filled. Click the "Add" button and type in a name, i chose "SFN", and hit enter. Then, with the new network selected click on "Edit", you should see this screen: First change the server from "newserver/6667" to that seen in the image, use the edit button and hit enter to finish otherwise it will not save. For the rest of the settings copy the image. Remember, unless you have registered with the server(I'll get on to that later) you will not have a Nickserv password. If everything has went as it should, you should see this window when you click connect on the first window with SFN(or whatever you called it) highlighted: Non-Essential Bits, Tips and Tricks. 1/Getting Someones Attention Now, even though it may appear like there are a few people on, they may not actually be paying any attention to the IRC window at that moment in time. For instance i may appear to be online but not be anywhere near my computer just because I forgot to close the window. All is not lost however as you can attract someones attention by typing their username(to get a hold of me you would type "insane_alien" without the quotes). This causes the entry in the taskbar to blink, if the person is there but is doing something else on the computer(perhaps being productive by playing solitaire?) they will see and check it out. Don't feel shunned if nobody responds imediately, we all have otherstuff to be getting on with and might not have noticed yet. It helps if you hang around for more than a couple of minutes to wait for a response, someone will be on eventually. 2/ Using Commands There are a few commands you can do that provide extra funtionality, for this example we will use the /me command. To use a command you just type it into the same place you would type to talk to someone. The /me command changes the way your text appears. It is usually used to describe emotions or what you are doing. 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a proper reference by our standards is a link to where you got a bit of information from. the places where you say 'it is said that' or when you are talking about 'psychological units'(another thread) and stuff will require referencing.

the atmosphere is pretty homogenous. as is the gravitational field, though we do have maps that show the slight variations of both. nothing that would cause antigravity or anything.

take 2 coins sit them on a book or something, one coin on top of the other. tilt the book slightly, if there was no friction then the top coin would slide off at the slightest tilt. however, i think you'll find that there is a significant range where the coin does not slide. this means there has to be friction there.

so, what is the question?

i haven't been keeping track of the rankings lately but strathclyde university has a decent chemical engineering department. just got its labs revamped too. </shameless plug of university he attends>

how can you expect an answer if nobody understands the question. how was my response absurd? i calculated the friction force with friction coefficients found in the literature. i then used newtonian kinetics to show that this force was indeed enough to accelerate the train.

i thought your question was that you couldn't understand how trains could stop on metal tracks? if we have misinterpreted then please restate your question and try to make it clearer. i understand english is not your first language so it may be a language barrier. Also, one little thing about my calculations i should have mentioned, that is for all wheels being powered/braked if not all wheels are powered/braked then the acceleration will be proportionally smaller.

i explained it, the wheels can apply a breaking acceleration of 7.26m/s^2 this takes into account momentum and such. just because you can't imagine it having enough friction does not mean that they don't. trains start and stop so smoothly because they do not apply anywhere near the maximum force before wheel slip occurs. they do it smoothly because the drivers are trained to do it smoothly. if you went in a train and jammed the throttle open instantly then i assure you it would not be a smooth ride.

uhh we've known europa to be icy for ages. hardly recent

unless you are processing large numbers of computers (hundreds of thousands per month) and are selling off non rare-metal parts then it isn't worth it. if it has a metal chassis selling that for scrap will get you more than the precious metals contained in it. except on massive scale operation the precious metals will give you a net loss.

Ed: the area of wheel contacting the track doesn't come into it. it just depends on the normal force. swansont: news to me as well, i just let it slip.

arguement from ignorance sums up that 'quest for right' thing perfectly, just because you do not understand it does not mean it isn't true.

oh theres more than enough friction. trains can start and stop faster than they do on the conventional brakes. they also have sand dispensers for emergency braking. i'll look up the friction coefficients and prove to you that there is enough friction available to stop the train. EDIT: here we go, Friction coefficients for steel/steel static: 0.74 (S) dynamic: 0.57 (D) source: CRC Handbook of Physical Quantities. Boca Raton, FL: CRC Press, 1997: 145-156. Static friction (Fs) Fs=S*N ; N=normal force Dynamic friction (Fd) Fd=D*N N=mass * g mass of a train ~200 tonnes g=9.81 m/S^2 as the wheels should not be slipping we use the static friction equation. Fd = 0.74*9.81*200000 = 1451880 N this is the maximum force of friction this train could take before the wheels slip. F=ma -> a=F/m a=1451880/200000 = 7.26 m/s^2 this is the acceleration at maximum friction. if a train accelerated or braked with this acceleration you would be flung out of your seat without being strapped in.

mind that ver much. if there is no real proof other than a few sketchy documentaries that were never controlled or subjectto scrutiny then the chances are it does not exist. ignore the man behind the curtain!

just because you are not good at a language does not mean you are not able to apply scientific method and learn scientific theories. i failed english, i'm in my third year of university and doing reasonably well.

rub two bits of metal together, plenty of friction. now do it with several tonnes sitting on it. unless there is lubricant(decomposing leaves on the track for example) there is plenty of friction.

i got a titanium watch. much better than gold. not a scratch on it