studiot

If the air pressure inside the balloon was not marginally greater than the air pressure outside the balloon would collapse inwards. Since the pressure is greater, the density must be greater and thus the mass of displaced air is less than the mass of the air inside the balloon, even without the basket and trappings. This is different from a rigid balloon such as a hydrogen or helium one where there is a positive bouyancy force.

Are you saying that the razor suggests Archimedes principle - which is of course an incorrect explanation ?

Carry on ?

Like Pullman's Subtle Knife perhaps ? Thank you so much for introducing a modern area of statistics I had never heard of - off to investigate! +1 Since you are interested his actual words were Which translates as It is futile to employ many principles when it is possible to employ fewer. But he did not say that the extra principles are untrue and all too often it is used as an excuse to reject the (more) complicated, whether justified or not. We are all a bit lazy and like to use the excuse "neglecting (higher order) terms as insignificant" This applies to my favourite engineering formula "something squared over twice something else" , which is not validated by the razor but by mathematics. But I would love to see the razor applied to the theory of flight of eg a human made mechanical aircraft, a butterfly, a hummingbird and a hot air balloon.

Translated this reads Things should not be multiplied beyond what is required. Yet no one has found this exact text in his writing that survives. It is true however that much of his writing echoes this sentiment. Howsoever it maybe the question is as in the title How true actually is it ? I posted this because members often appeal to this maxim for support.

So how is it 'confined' ? In MRI the water is confined within the patient. What do you think the R stands for in MRI PRI and NMR ?

That is not my understanding of the working of MRI or othr NMR machines, nor how it is described in your link.

We don't do you homework for you some of us help you to do it ! It is important that you work through as many convertion examples as you need until you can 'do it in your sleep' . There is no other way to proficiency. Please note that new members are only allowed a total of 5 posts in their first 24 hours, to help prevent spammers. After that you can post as many as you like. Go well in your studies.

Note you can use superscript on this forum Scientific notation usually means a number between 1 and 10, for which we don't write the power of 10. So strictly your answer to should be 1.5 μL However many scientists also allow or just write 20 as just 20 not 2 x 10, So they are choosing numbers between 1 and 100. Engineers use numbers between 1 and 1000 and that is the basis of using only milli and micro and kilo.

OK thank you it was in biochemistry. And it was one of many general practice questions. I asked about pharmaceutical calculations because some medicines are supplied as a particular mass in a vial to be diluted and then added to an infusion bag of particular volume. Such questions would be almost in the format of mass to concentration by volume. And there was a slip up with question 5. So check that no addendum was posted and inform your academic supervisor. Chenbeier was correct. +1 For others who might be interested here is the excerpt from the pdf.

No, please post the complete correct question. Then we can help you with your units. You have posted in Chemistry, is this in fact a pharmaceutical calculation and is it coursework/homework ? +1 to Col for attempting to help.

Firstly this post seems to confirm that this is about computer programming so I don't know why you have placed it in Applied Maths, not Computer Science ? But thank you for the reply, +1 , which is much more understandable and would have saved two weeks of floundering discussion if you had posted this in the first place. As to the substance of it. It is interesting that what you are trying to do is an updated version of my (ironic) patented method of passing exams in kinematics from the 1960s. In more modern times (the internet and more recently smartphones) many such 'calculators' have been offered for example Chemists can easily find pH calculators and Doctors/Pharmacists can find 'volume of distribution' calculatiors online very easily. Even more advanced is the Wolfram Alpha and associated site which offers a sort of 'online mathematician' you talk about. But these are just tools that should not be used blindly The user should know and understand the subject to hand. A second thought occurs to me, you have mentioned that some folks find plain English more understandable than a formula or bunch of formulae. I agree. But yet other folks, myself included, find pictures and diagrams even more informative. I had (still have but sadly cannot now deploy it) a program callled DesignView. This was an amazing program for its time, but serious hampered by the limitations of the computers of its day (Windows for Workgroups no less). In essence the user is provided with an entry screen on which she can place directed line segments (vectors) graphically, thus describing say a structure or dynamic system. The computer automatically turns this into an appropriate set of equations and solves them. The user may then play about with the subject either by directly editing the equations or changing the line segments in the graphical model. Non linear equataions such as spline curves may be generated and there was an animation section to the program for dynamical systems. More recently other graphical system modelling programs such as Visio, CircuitMaker, Spice etc have been released. Traditional drawing programs such as AutoCad have added some of this functionality. There are also intermediate programs such as MathCad and Mathematica, ChemDraw and Chemsketch. Many of these require considerable investment in time and effort for profficiency. Alongside this Finite Element programs have become more user friendly with half ways decent GUIs. Yet again the GUI is not the be-all and end-all, that many think. I remember in the 1970s visiting the Hydrographic Office of the Navy where they were starting the mass digitisation of Admiralty Charts. They ahd developed a voice command system for editing the digital chart, so a new wreck, a new or shifted sandbank etc could be added at the speed of light in comparison to the old system (I don't know if you are familiar with the system of 'Notices to Mariners') So it would be interesting to learn where your proposed AI fits into all this ?

I see you are still on line so I will try to make this quick, but it may be a bit jumbled as a result. So carry on asking questions. You do not really need vectors or Newton's Laws to understand the Physics of this. The man in the trick is a single bodythat mey be considered as a single entity. He has no direct contact with the ground (or anything other than the truck). So pushing against the truck floor, as well as one side, is the same as pushing against the opposite wall of the truck or any other part of it. The is no overall or net effect on the ouside world. The fundamental physical principle is that internal forces always cancel or balance out. This is illustrated by the following. If you stand a book on a table the book exerts a force on the table due to its weight. If you stand another book on top of the first one then this book exerts a force on the first book which then transfers the extra weight to the table. Internal forces within the book cancel out. Can you draw a diagram to illustrate this ? It would help you to try first, then I will offer one. If you

I was going to say why do you not give us an example ? but re - reading I find you already did that but that your example is as obscure and impenetrable as the rest of your question. I agree that is sounds good in principle to ane the variables more meaningfully, but consider this: This was actually the way it was done years ago so Newton would have said, "Distance is proportional to time" (note they did not use equations in his day) This sounds better than s = ut doesn't it ? And further this is what is taught junior school. BUT What about s = ut + ft2/2 How about putting that into words ? Which would you rather learn ?

Yet another thought. I was thinking about the usual british house/garage layout with the garage either integral with the house (under a common roof) or adjacent to the house with a common wall. If the garage is actually a separated outbuilding then additional requirements apply, not least an extra isolation switch and the means of routing the supply cable The garage wiring cannot then be part of the house wiring directly. So it would be advisable to plan for the electrical work before the building work is done.

A further thought, he should consider adding an electric car charging point. That would add to the value of the property and he may be able to get a grant for it (about £500 I believe). That would definitely have to come off the main dist board as it is nearly equivalent to two ring mains by itself.

Now is the need for more information. Most properties have their meters/distribution box('fusebox') in or around the garage if they have one. It would certainly be better (and safer) if your friend could run new wiring from there. Is he proposing to get a board certification of alteration for this ? Sadly beaurocracy is steadily increasing these days, without any corresponding increase in safety

Sorry not directly no. You can have more than one spur off a ring main but only to one outlet (remember that can be a double) You cannot extend the spur to another socket. But there are some ways round this as in the hasty attachment.

How nice it is to have a pleasant converstaion with someone. Yes I am too old and lazy to learn LaTex or MathML properly so I use a commercial program called MathType. Here is a screenshot of me setting out a 3 x 3 array MathType give the option of copy/pasting in various versions of LaTex or other markup languages such as MathML. I use the MathML output on SF. Unfortunately MathML is quite expensive. So here are some sites which offer free online Tex you can copy/[paste from http://www.sciweavers.org/free-online-latex-equation-editor https://latex.codecogs.com/eqneditor/editor.php The only forum I have come across which offered direct LaTex in the editor was AllaboutCircuits dot com, when one of the administrators here at SF was administrator there. It was a bit 1990s clumsy but could be made to work. So come on @Dave and introduce it here. Final thing, Due to a glitch in SF software preview doesn't render Tex properly, you also have to refresh your page when viewing Tex initially. Hope this all helps.

Surely the basic Physics comprises the 'invariants' of the Theory ? In SR the invariant intervals form a network that requires no coordinate system whatsoever. In fact the addition of any coordinate system adds restrictions that are not present in the physics, in the similar way that the introduction of coordinate geometry restricts the geometry of Euclid. For GR the invariants are different and still being worked on to this day. https://en.wikipedia.org/wiki/Curvature_invariant_(general_relativity) https://link.springer.com/article/10.1007/BF02726036

Thank you +1 Still on your high horse I see. Building literature is full of examples of failures of tanking on the insides of basements due to external water pressure. I suppose I had better say that there are also other failure mechanisms as well in case you again think I mean all or nothing. Equally there are circumstances (not applicable to the OP) where internal tanking is the correct approach. For instance swimming pools, slurry tanks and other industrial fluid containers. The main point with the is that insufficient information was availble to pin down the reason for the tanking so I tried to offer an series of alternatives depending upon more information to be as helpful as possible to the OP and save a lot of questioning if he ever came back.

It's a pity you won't listen to others as your idea has the germ of truth in it. But not as you appear to expect. Strong and weak are relative terms so that neither of the above statements are absolutely true. But your idea that the force experienced by other charges varies with aspect for atoms (and molecules) is one of the most vitally important subjects in chemistry as it controls both chemical bonding and chemical reactions. Perhaps you should ask about this as the level of maths required is probably within your grasp.

But I was not wrong. That's the whole point.

It should be noted that a differential manifold does not mean the manifold is differentiable. It means that at least some functions defined on that manifold are differentiable. It does not mean that the coordinate system is differentiable - that has no meaning eg the statements x, y or the x - y plane are differentiable are meaningless by themselves. They are short form for functions lying in the x - y plane are (or are not) differentiable. The x - y plane itself is quite indifferent to whether some function is differentiable. A similar point can be made of continuity, but it is more complicated. Functions are 'continuous' or not as the case may be. Continuity for the space in which they lie has been broken down into lesser concepts of which connected is probably the nearest. Topologically a circle may be 'continuously' deformed into a wiggly loop. No metric or coordinate system is necessary for this. Topologically we talk of transformations rather than functions, although they are very similar.

Yes like I said, I gave you full credit for discussing ventilation. Are you suggesting I didn't ? You have yet to address my other point, responding you your vile and base attack on me, as you always seem to to.