studiot

Searching doesn't find any useful help on this so how do I post a table here please?

So, Talos, your University link says that you were wrong and everybody else was right.

@CasualKilla How did your brother's exam go? I would appreciate it if you posted the exact question as written by the exam board or whoever since there may be something in their wording we have missed, that leads to the solution you say they sent in a memo? Textbooks are rarely wrong in their published answers, Exam boards even more rarely wrong.

If you have anything to say, say it here. Or do you deny the rules of Science Forums as well?

I am aware of the laws of hydrostatics. But that doesn't matter to the question I asked you or to Newton's laws of motion or to the Laws of thermodynamics. Particularly as you denied their truth

You would have to ask a botanist for an explanation, but my Chambers Scientific Dictionary has: Anodal or anodic (Bot) In the upward direction on the genetic spiral. There is, however, no impasse. It's just that some engineers seem to have forgotten what we regard as the internal cicuit and what the external circuit and mix them up. It is important to understand which is which because directions are reversed for these two parts of a complete circuit. So they cheerfully take a battery, write + on one terminal and draw conventional current passing out from this terminal round the 'external' circuit and back into the battery at the other one. Yest these same engineers then take a vacuum tube, mark one terminal + and cheerfully show conventional current entering the valve at this terminal passing through the valve to the other terminal. Strangely they want to call both these terminals marked + the anode!

You are so nearly there it is a shame if you don't want to listen. Or are you, perhaps, just repeating something you half heard sometime ago? You have a balloon sitting limply on the ground, showing no signs of going anywhere. Newtons First Law : A body continues in its state of rest or steady motion unless acted on by a (net) Force. So the limp balloon is not being acted on by a force. You come along and inflate the balloon so that it rises off the ground. So Newton requires there to be a force acting on the balloon. Can you name this force and describe it please?

No I do not agree with your chain of 'reasoning' and I have already stated why. You state that the balloon causes the atmosphere to rise. Why so? Suppose I removed some air adjacent to the balloon (perhaps by freezing it) and equal in volume to the balloon, Would the atmosphere now rise? Would the balloon still rise when released? What would happen if I filled the balloon with carbon dioxide instead of helium by mistake? Would the balloon skin not still push back the atmosphere by the same amount? The point is that the apparatus that inflates the balloon causes the balloon volume to increase against the pressure of the atmosphere around the balloon skin. Work is done against this pressure and is equal to the volume change times the pressure. Since this work is done against the atmospheric pressure energy is transferred to the atmosphere as pressure energy, not gravitational potential. That is what I mean by saying that you need to distinguish types of potential energy. I also mentioned bouyancy force. This is independent of the balloon (once inflated) and is the same upward force regardless of the weight of the balloon. So if the weight of the balloon is less than the BF the balloon will rise, and Newton's First Law is not violated. Work is then done by the bouyancy force minus gravity on the balloon. This work appears as increased gravitational potential energy of the balloon.

Which is exactly double the correct answer. Not quite. positions (2) and (3) could be vowels or consonants. position (4) is specified as a vowel. imatfaal What would happen if you only had an alphabet with two vowels, but otherwise the same question? it is because the fourth one is specified as a vowel that you cannot reorder. By this reordering you can separate the 6 character word into three independent segments. But you cannot do this when the final letter is specified as a vowel. In your reordering you definitely have 4 vowels available to choose from in position (2) In the original you may have 4 or 3 or 2 This difference must be reflected in different probabilities for the second specified vowel.

No problem. I don't recommend using the abbreviation p(4) for position 4 since p(something) is normally used for probability(something). Think of your tree (No I don't wnat to draw one either) Position (1) has 5 branches Let us say postion (1) is an 'a' This must immediately strike other branches that contain an 'a'. So you have a smaller tree than if 'a' was still available. It is exactly the same for whatever vowel goes into position (4) - it must make this vowel unavailable to other branches by striking them out. It's just that we don't know which one, but it doesn't matter since all the branches have the same pattern, there must just be one fewer for every other letter position. So we have (26 - 2) = 24 in the second position. In the third position we have already struck out the branches that are used by position (4) so we don't need to do it again. So we simply take one off the available total (it could still be a vowel) 24 - 1 = 23 position (4) the second vowel now comes after 3 preceeding characters have been chosen and these three could all be vowels, leaving 5 - 3 = 2 available vowels. I asume you are OK with the 9 and the 8 for positions (5) and (6) ?

Did you mean the 2 at position (4) or the reduction of 2 for position (2)?

OK So Position(1) is a vowel and can therefore be chosen in 5 ways. Position (2) can be a vowel but cannot be the vowel in position (1) or the vowel in position (4) (although we don't yet know the second vowel) That means there are 2 (not 1) unavailable letters for position (2). That means there are 26 - 2 = 24 available letters. Can you now complete?

No I have already said the memo is not wrong. Fiveworlds has already said he is just guessing. Have you tried following my method?

Casualkilla do you wish to continue, despite the incorrect interruptions?

Note your memo answer is the product of 6 factors, and you want a 6 character password. Is this a coincidence? The first character is a vowel. There are 5 vowels. So how many ways can this be chosen? So work through the first, second third etc asking each time the same question.

Yes that is quite true, but that is also not the system employed here. For prestressing the stressing force to the stressing wires is applied before the concrete is poured. This is done between external fixed anchors, which must be strong enough to support the prestressing force. The concrete is then cast and as the cement reactions proceed the paste shrinks around the wires and binds firmly to them along their entire length. Once the concrete has hardened in this condition the support anchors are removed and the wires attempt to shrink back to their original length. However they are firmly grabbed by the concrete and remain stretched. So the prestressing force is balanced by a compressive force, developed in the concrete. No external agent is then required and the lintel may by lifted and built into place. Motorway beams and building floor beams are manufactured on this principle. The alternative is the cast the concrete first and let it harden. Then the post tensioning is applied via a cable (or rod) external to the system. Usually no external anchors are required the reaction is obtained directly from the concrete being stressed. As to the inner working of the patent official's mind, I can't answer that one. I remember Joe Lucas trying to steal a march on other battery manufacturers, back when most auto batteries were housed in heavy rubberised glass containers. They managed to obtain a patent for "Battery cases les than 2mm thick" for their plastic case. And they tried to charge other manufacturers on the basis of this.

Yes that's a good way to put it. The difference between prestressed and post tensioned concrete is that the anchors become redundant in prestressed concrete.

It is, but it is a very useful fictious force as it transforms a problem from one of dynamics to one of static equilibrium. It is known as D'Alambert's Principle. This link is simpler than Wiki for a first reading http://www.britannica.com/EBchecked/topic/150132/dAlemberts-principle

Actually, John there is more to this idea than post-tensioned concrete (It is post tensioned, not prestressed). The post tensioning is carried out against a ground anchor and the whole system depends upon the stability of the ground anchor in the seismic disturbance. This is not, however, new.

I'm sure I know substantially less than ajb about this but I do like the term 'kittygory' for 'small category'.

I don't follow what this has to to with either order or entropy.

Potassium Chlorate is poisonous (used a weedkiller); it is also dangerous for other reasons. If you do not already know the answer to this you should not be 'experimenting' with this substance.

I wasn't convinced by this link since they only mention 'cathode' once, as 'cathode materials', and do not indicate a polarity. Farady introduced the terms anode and cathode in the 1830s, along with his two laws of electrochemistry. Here is the modern version that has been in continuous use since that time by the whole electrochemical industry, not just the battery section. Taken from Moody's Comparative Inorganic Chemistry. I have highlighted the definitions.

If you look carefully at the picture in the first link in my post#3 you will see that this definition also conforms to the (electro)chemical definition, ie they are the same. Electrons are shown leaving the zinc anode. Further down there is a picture of an (i'm sure familiar) accumulator. Unfortunately it is probably (no disrespect meant) beyond auto techs to understand that the accumulator acts as two different devices when it is charging and when it is supplying current and that the terminals are simply the lumps of metal, but the names anode and cathode are defined by their function, not by a particular lump of metal. So that the terminal names should therefore be reversed when charging and discharging. So auto techs call one of the lumps of metal (terminals) the anode and (wrongly) stick to it. For a battery being discharged, the terminal marked + is the cathode, while for the same battery being recharged, the terminal marked + is the anode. The Zener diode is an unusual case since it is normally operated in reverse mode. However it does work as a normal diode in forward mode where the definition works. So a simple approach is to say that since we are talking about reverse current the reverse definition applies. Alternatively a good discussion is to be has here http://www.av8n.com/physics/anode-cathode.htm

Sorry to have caused the confusion, I have editied my previous post to what I should have written. Rectilinear = in a straight line Curvilinear = in a curving line The linear part = line and the prefix tells whether the line is straight or not. As to the abrupt part I suppose a rolling irregular object could have corners that follow a cuspate path and thus suffer abrupt changes of direction.