studiot

Jamsmith Oh ok, I am grateful to you for your more precise discussion. Does it work like this? How does it apply to a catherine wheel or a lawn sprinkler?

I think you are trying to make this too complicated and should go back to the basics of SHM. You have too many terms in your equations for SHM. Further you have not responded to my hints in post#3. Your equations are overcomplicated because you conditions are inappropriate. You have yet to place the mass at the beginning of then process or establish what is meant by 'the mean position'. Bender asked you to state the original question you are trying to solve as written. Please do so as I wonder if you are not missing something out? Quite separately, I have started a thread in Feedback to try to get some help with placing images here.

This extract is from a recent thread; it refers to an issue that is by no means unique to that thread. I don't know how incorrect orientation could arise and was obviously not the poster's intention. Whether it was due to the origin of the pic being a mobile phone or tablet or something here at the forum. When the issue is resolved perhaps it could be flagged up in some way to help others in future?

Well spotted, thanks, +1. That was an embarrassingly silly slip.

Good evening Kevin, and welcome to SF. You certainly seem to have got into a tangle with this one,despite a lot of correct thinking. Is it homework? We have special rules about homework help. http://www.scienceforums.net/topic/75772-read-this-before-posting-in-homework-help/ Anyway Yes the first step is to convert all to the same units and 104 picofarads equals 104 * 10-12 = 10-8 = .01*10-6 farads or 0.01 microfarads. I laboured this because you seemed uncertain. All four capacitors are actually in parallel. If you look carefully, you can see that each capacitor has one connection directly to each terminal. A good way to see this is to delete three of the capacitors, but leave all the wiring intact. It is then easy to see that the remaining capacitor is directly connected across the terminals. So you need to simply add up their values as you correctly surmised. So, working in microfarads, we have 0.1 + 0.01 + 0.001 + 0.01 = 0.121 microfarads as your lecturer said. As another tip for a more complicated circuit. The right hand two capacitors form an easily recognisable parallel pair So combine these first to one equivalent capacitor before dealing with the crossed over ones. Then you can see that this equivalent capacitance is connected across (ie in parallel with) whatever the net result of the crossed over capacitors is. In this case they are also in parallel but they may not be for a more complex circuit. So you work your way through in simple steps, reducing the complexity wherever you can. It takes some practice to sort out when something is in series and when it is in parallel. Two further tips. Label your diagrams clearly and unambiguously so C1, C2, C3 and C4. This makes it so much easier to refer to the elements when someone is discussing them. Secondly this site allows you to write exponents directly using the superscipt and subscript icons in the entry box toolbar. That is such a boon.

Can you please post your pics the right way up? It is a nuisance to turn them round. You have not made it clear why there should be any oscillation at all. In other words why will the spring not simply stretch until there is a balance between the electrostatic attraction and the spring force? Note I am not saying there will be no oscillation, just that you haven't established the conditions for it to occur.

So are you only referring to gravitational mass or did you miss my post?

Are you sure you do not mean negative effective mass? This is a well documented and respected concept that can be used to explain some results for example in the Hall Effect.

There is another misconception that underlies this (OP) question and is evident in many of the replies. This is forgetting that the centre of mass of a rocket system does not move or that a body cannot spontaneously propel itself through a void.

Good morning, Nancy and thank you for your contribution. Since you haven't asked a question I will ask one. Entropy may change in the formation of a snowflake, but what about symmetry? Does it change and if so, does it increase or decrease? The reason for the correct answer to this stems from the same reason that a snowflake is more 'ordered'.

In which case surely your X and X' and the flatlines beyond them should be on the zero line? Initially said said that the acceleration was initially positive up to O and then negative afterwards, so I would expect to see your triangle part above and part below the line. A word about English and terminology. In ordinary English massive means having very large mass, which is as you seem to have used it for M1 and M2. In scientific English massive means possessing any mass at all, however small, so a neutron or a spaceship is massive, a photon is not. In circumstances like these the neutron or spaceship are called the 'test mass' in scientific English. Finally you have (correctly) posted in the classical section and refer to Newtonian mechanics. But even in Newtonian mechanics you need to consider the motion of M1 and M2 as well. Why would m pass along line XX? By the time m has reached the midpoint between M1 and M2, they will have, in general, moved somewhere else unless all three objects are tied to some other (larger) one. This is rather like the Earth, the Moon and a spaceship all possess a common motion about the Sun so we can make the motion assumption you have made as the spaceship moves across between Earth and the Moon.

I am going to start this again to correct some errors you have made right at the beginning. Is this homework or are you trying to understand something you copied (wrongly) in class? Or are you struggling with English? These questions are meant to help since your first equation is impossible. If W is the moment of resistance then it does not have the dimensions of L3, which the equation you have written does. I will derive the correct equation, using the attachment which shows a section taken through the body at . The moment of resistance is defined as the moment resisting the couple generated by the compression © and tension (T) forces acting longitudinally within the body, due to applied stresses (Sc and St). By horizontal equilibrium C = T and the couple = MR = Ce = Te where E is the distance between the forces C and T. Since the stresses increase linearly with distance from the neutral axis C and T act through the centroid of the stress triangle as shown. This is at a distance 2/3 of the way from the neutral axis to the outside edge in each case. That is 2/3 of b(x)/2 since the neutral axis is halfway between the edges. So e is twice this distance. Now Sc and St are the maximum stresses, found at the edges. The average stress over the whole area is half of this ie (0 + Sc)/2 and (0 + St)/2 The Forces, C and T are found by multiplying the average stress by the area, which is shown in the right hand diagram as b(x)/2 *b(x) in each case. Thus we correctly find that the moment of resistance equals the max stress times (b(x))3/6. Please confirm you have understood this so that we can continue.

#So how about the other circles question I mentioned in post#7?

Better to tell us what led you to the conclusion that something is changing with respect to placebo trials. I, for one, am interested in the beef (remember that advert?)

Why not? (edit) You are right, it is a trapezium, CEDF is the parallelogram But Sriman's proof is otherwise valid

See how easy it is for misunderstandings to arise? I'm not Gary - he is a Professor formerly at Yale now at Pomona. and the author of the Applied Statistics book I referred to.

This is the first time I have looked at this thread as it concerns a subject area I am not usually interested in, but seems to have generated a deal of activity. I have two things to observe. 1) The issue of cutting / pasting and links. The settings on this and some other sites interact adversely with the settings on some windows computers so that the quote button and the paste function do not work. We have more than one thread (including one of my own) involving attempted help from the administrators, moderators and others but despite all the suggestions I still have one Toshiba Satellite Pro laptop that originally sported Windows 7 (now 10) that always suffered from this issue, which has never been resolved. I did resolve it on a Dell Vista machine by reluctantly using a different browser and this may be your only option as it presents a barrier to effective communication and is a bloody nuisance as well. Alternatively perhaps you can make one (trial) post from a different machine just for the links? 2) After 5 pages of squabbling where everyone retreated to isolated fortifications and pulled up their respective drawbridges I have learned that the OP wants to discuss alleged indications that large scale drug trials are somehow becoming less effective. This is straightforward applied maths that does interest me and there has been significant level of publication over the last 10 years or so about this. Both by Doctors https://en.wikipedia.org/wiki/John_Ioannidis https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1182327/ and by other acedemics Standard Deviations - Flawed assumptions, tortured data, and other ways to lie with statistics. Gary Smith I look forward to the OP response, including references to some real material to discuss. Dave, if you are still having trouble pasting in then I will see what I can do to help, though not with vague invocations to perform searches.

You need to provide sufficient information such as the relationship between l and b, and the loading conditions. Short stubby beams behave differently from long thin ones. Since the beam is tapering the loadings also play their part.

It's best not to argue with the referee. I understand your technical point and it's wrong. Have you never played 'tug of war'? There is no reason why a 'pull' can't be the resultant of two or more 'pulls'.

I don't think anyone will mind now, the question was so long ago that the OP cannot claim credit at school for it. There have been 163 views so we are addressing others who may like to know.

That's correct, Sriman. So can you complete the proof? Can you also complete this second one? http://www.scienceforums.net/topic/103844-circles/#entry975863

The chord modulus - also called the secant modulus. Last time I looked there was no standard method - which is why this extract says you should always state the points it is taken from.

Yes but it depends what you (and the OP) mean by "The Rocket". I am simply trying to point out that this is not a fixed object but is continually changing throughout the flight, unless you include the exhaust. Which I suppose is another way of say the same thing.

Reconstruction of past events and periods can be difficult and complex. Sometimes different indicators point in different or even opposed direction. First here is an extract about Chicxulub from a book that is a masterpiece of balancing all the conflicting evidence. This suggests that there is definite geophysical evidence for the activity reaching and affecting the mantle, though there is no suggestion that the meteorite survived even partially intact, like a bullet. Now to suggest that shock waves from this event which was effectively instantaneous somehow initiated up to a million years of successive lava flows require that it occurred before the lava. These recent references suggest otherwise. The impact http://www.livescience.com/26933-chicxulub-cosmic-impact-dinosaurs.html The Deccan https://www.princeton.edu/geosciences/people/schoene/pdf/Schoene_Deccan-Traps_Science2015.pdf Returning to the book I referred to unfortunately it is mainly about the Permian/Triassic boundary extinction but does provide an unbiased examination of the available evidence at its time of writing for other significant extinction effects, including the KT one in question. The techniques and trains of thought are worthy of examination. Paleontological, paleobotanical and so on evidence should be examined in both land, sea and air enviroments as well as evidence from inert matter both in type, disposition and mechanical, chemical and or thermal disruptions. Any proposed mechanism should be tested against the known geographical distributions of the land masses at the time of invocation of that mechanism. Are you talking an S or P wave? I can see the idea of an S wave temporarily opening a preexisting weakness to allow the exudation of magma, which then forced a widening of the breach and further outflow. Do you mean a true shock wave, which is the result of something material travelling fast than the local speed of sound, or something different? I agree with Argent the language is rather over dramatic for a scientific discussion. Remember also that the proposal is a hypothesis; a theory is rather more.

Thanks sensei +1