studiot

This is a misapplication of the Law of Conservation of Energy. COE (the First Law) applies to changes in state function energies, due to inputs or outputs to a system summed over some parameter of the process eg time, at the end of a process. It cannot be applied directly during a process.

Yes by the use of a virtual work analysis, Faraday's, Lenz's and Neuman's laws can be deduced from conservation of energy and a virtual work perturbation.

A very good and deep point worth a thread in its own right. +1 By its very definition and nature the end point of an evolutionary step is not equal to the starting point. I don't agree with the rest of the post, however.

Yes Yes Yes Yes Yes Yes +1 PS I resisted the temptation to reply six times

Twp disputes is two threads. Plus one more for your dispute with swansont. I look forward with interest to spectating.

I seem to be the only one who reads books these days so here is something I didn't see on facebook or twitter. It is about cleaning keyboards, but I have also applied it to mobile phones and computer boards more generally, but take batteries out first.

Thanks for the replies, even if I don't fully understand them. Are they anything to do with Science? Can I tag the single malt in pictures now?

I note I can now write a public message to another member. What does that look like and where does it appear please? Does this mean there are no longer any private messages? What about the little envelope icon. What sort of message is this?

Yes it is irrelevant to the force in the bolts, but not to the changes of length and strain and hence distance measurements. I assume that was why you (rightly) asked the question how were the distance measurements made. The OP states "I want to calculate the 'deflection' at this point on the surface". But the deflection from what? A surface plate the whole assembly is standing on? The contact surface between the sole plate and the block? I agree that between any two sections or marks on the unstressed block, the compression will only depend upon the applied force, not the method by which it is applied. However something must change position in the system, so if measurement is made from an external reference, this must be taken into account. A question for varatharajan. It is possible to have stress without strain or strain without stress. Can you say how?

1) There are two bolts so F = 2 * 50kN 2) Your section BB is shown looking up into the thicker part of the block including the overhang. You should be using the area not including the overhang. 3) The tension extension of the bolts and the compression shortening of the block are of the opposite sign. How this affects the measured distance between the sole plate and the overhang depends upon the method of measurement and the foundation conditions of the sole plate.

If you prefer to use a formula to calculate the bolt force, the standard one is T = c*d*F Where T is the required tightening torque d is the bolt diameter F is the initial bolt force c is a constant, default value 0.2 Use of the default value leads to the 50 kN mentioned by Bender. Using this, and deducting the bolt hole area from your stated area I make the calculated shortening 0.005 mm. Good site linked BTW Bender. +1

Do I really need to know what swansont is doing every minute of the day? Do I really need to know when some ratbag spammer joins the forum? Do I really need a list of the last 15 replies to a very active thread? I certainly don't want to know any of this. But what was needed and readily availble now takes me several screens to find and I still can't be sure that I have checked the threads I have an interest in.

My mistake. Thank you.

Maybe it doesn't like your spaces, MathJax won't parse your code for me. However [math]y = \int {f\left( x \right)} dx[/math] But you have to click on page refresh in your browser to get MathJax to activate. SF has stooped to the (low) level of other forums.

+1

I am guessing here because the OP is far from clear but I think the OP is referring to tightening down a block onto an unyielding sole or ground plate with his setscrews and a torque wrench. This will obviously cause an elastic shortening of the block, which he refers to as the 'deflection'. There is no reason for the block to bend, unless other unspecified forces are also acting. However, varatharajan, you have to give the dimensions of the block and specify its material to solve this question. Since practical measurement was mentioned, it is necessary to torque those screws up in stages or ther will be some warping forces involved.

Just so true. If Muskan does not know what an electrical current is, then he may well not know what a potential difference is either. A potential difference is often called a 'voltage', but you have to be careful to find out if something external is providing the voltage (eg a battery) or whether there is an internal voltage created. The first type of electrical current to study (there are others) is carried by moving electrons. So there must be a source of electrons that can move about. These can be generated by applying heat or light or enough externally applied voltage to a physical object. Left on their own a collection of mobile electrons will just drift about, trying to get away from each other since they all carry the same negative charge. (Remember like charges repel) Heat and light do not move the electrons in any particular direction, but applying a voltage does. This voltage drives the electrons away from the negative terminal and towards the positive one. The greater the voltage the bigger the effect. I also said that applied voltage can release mobile electrons. This is how we get sparks and the discharge in flourescent electric light fittings. So applying a voltage directs the current in a way that we want. Doing this is often likened to water in a hosepipe, but it is a very bad analogy because if you cut an electric cable, the current stops instantly at the cut. But water will trickle out of a cut hosepipe for a long time after cutting. If you understood this we can move on to other forms of electric current, in some of the different things Ed Earl mentioned (or perhaps he will tell you)

Looking over the past hour 7 trash threads started 1 real thread answer posted, but I have to scroll my screen to see it We had all hoped for heavier trash swatting with the new look, but it doesn't seem to have arrived yet.

This is consistent with this graph from Beerling. Note the age of the triassic 250 - 205 MYA, long before the end of the dinosaurs at about 60MYA

test mathType [math]\nabla = \Delta [/math] Codecogs \Delta =\triangle = \triangledown [math]\Delta =\triangle = \triangledown[/math] Sciweavers \Delta = \nabla = \triangle [math] \Delta = \nabla = \triangle [/math] Edit Looks just like the mishmash seen on other tech sites these days. and I have to press refresh page to get mathjax to kick in

The notification of another reply appearing whilst you are logged into a thread still works.

I see pagination and a sensible list of users online now showing. Thanks I have to observe that whoever wrote this version seems to have left CR and Dave to do all the real work and concentrated on unneccessary prettification. I feel for you both.

A very good point and what's more I hope that pagination has been retained. +1 My experience with super efficient sites is that if there is no pagination as you scroll down a thread the pages gets 'heavier and heavier' (ie slower) the further you go. So what about some of the SF threads that are 1000 posts long? Finally that blasted notification box has struck again. As soon as I logged on I got a notification that Ca'nRefsmmat has quoted me 1 hour ago. Surely you are not going to waste all that computing power telling every member every time someone quotes them? Think how many quotes are used here by members.

Fiveworlds +1 but I can't reference your post I'ts good to have a programmer or three with us. @The bosses, BTW I accidentally clciked twice on the green heart for 5worlds and a rather peremptory notice came up "you are not allowed to give reputation to this user" Could you not soften this message to something more human? Some of the other messages are more like from a Victorian germanic schoolmistress, rather than seeming to want to be friendly and helpful.