Explanation Definition and 982 Threads

Please look at picture for details... Is the reason why Force (F) does not create a torque when applied at the given point on the tire because it is pulling against the axis with a Force (F) towards the right and at the same time the axis pulls back with an equal force magnitude but opposite...

Why is it that when i cook sausages i can brown them on one side, but, when i turn them over to brown the other side they turn over on there own. I am sure there must be a scientific reason, maybe steam trapped under the skin, any way the only way i can cook them all round is by sticking...

So I have an elementary understanding of group theory and the goals of studying sets and operations on them but I noticed that along the way, my understanding of a quotient group is severely flawed. I understand what a so called normal subgroup is, but could someone please give an in depth...

Please look @ the pictures below. I have drawn a master slave D flipflop with preset and clear option as mentioned in the book. http://i28.lulzimg.com/7e22bfc016.png Can anyone tell me what is the necessity of the wires that are highlighted in the image? isn't the wire @ last stages of...

My 2 year old play with the following toy at our home. https://www.amazon.com/dp/B000GKD006/?tag=pfamazon01-20 It is basically, when you put the correct animal block in the correct place, it makes the sound of that animal. I can see some sensor in the wood piece and in the board; it can...

Hello. I'm trying to understand why, in terms of Maxwell's Equations, the ratio of the number of turns in a transformer converts an input voltage to an output voltage. EE explanations only seem to go as deep as this article: http://en.wikipedia.org/wiki/Transformer#Basic_principles They state...

So in the twin paradox, the traveling twin ages less in the end. According to time dilation, each twin sees time passing in the other twin's frame of reference slower than his own. However, if the twin on Earth is ultimately older, doesn't time have to appear to be moving faster for the twin...

Thin-Film Interference: Coating a Lens -- Answers found, explanation needed! Homework Statement Boxed answers are the correct ones. Homework Equations 2L=(m+1/2)(λ/n) for constructive interference (maximum reflection, bright film) 2L=(m)(λ/n) for destructive interference (minimum...

About 25 years ago I had a very unusual experience which I've never been able to explain. I was in a restaurant with my Mum one day, she was chatting, I was listening. Suddenly I see a wave come from her head going across the room, it was a sine wave. Interesting hallucination I thought to...

Hi, I am facinated by the http://en.wikipedia.org/wiki/E_(mathematical_constant)" and how it shows up in natural processes. However, I have never been able to comprehend its defination. e = lim n→ ∞ (1 + 1 / n) ^n I think like this ( and I know this is not correct): If n...

When two persons meet each other in one point, one standing still (can be moving too) and the other moving (compared with the other) and in that point a light wave has started 90 degrees up and reflects (mirror 0 degrees), both persons will see the light wave back, the moving person in another...

I understand that having a periodic signal x(t) we can find a signal y(t) which uses harmonically related exponentials in order to construct the x(t) signal each exponential has a frequency and magnitude, for example 3*e^{j 2 \omega} has a frequency of \frac{2 \pi}{2 \omega} =...

Homework Statement A girl can row a boat at 3 m/s in still water. She wishes to cross a 165m wide river in which the current flows at 1.5 m/s. Find the direction in which the boat must be steered in order to cross the river: a) by the shortest possible route b) in the shortest possible time...

Hello everyone, thanks for reading. We all know that Quantum mechanics can be "ignored" when working with systems in which the typical distances and energies are big enough (compared to h, or other quantum constants). However, when I try to think of an explanation for it I'm not sure I hit...

I am a lay man but having lot of interest in understanding about out space & universe. In connection to that, I need a explanation for my confusion regarding light years, which is denoted for mentioning the distance of an object located far away from the earth. Let say a star located a light...

Good afternoon gentlemen/women, I have a question regarding Lawrence Krauss' talk called "A Universe From Nothing" (Which can be found at ). In the talk, Krauss says that quantum fluctuations can produce a universe. He mentions that if we were to observe this happening, the universe from our...

I just read the following passage on unification from Howard Georgi: "The SU(2) x U(1) theory is not particularly beautiful. It is often called a unification of the weak and electromagnetic interactions, but, in fact, the unification is partial at best. The problem is the U(1) charge...

I've basically read that refraction happens because when a part of a light wave enters a medium where it displaces faster or slower at an angle, the part in the new medium "bends" the light wave because of the change of velocity, basically "turning" the whole light wave. I've made two diagrams...

Homework Statement What is meant by lateral displacement? Homework Equations The Attempt at a Solution

Hey All, I have been working on some Metric Space problems for roughly 20hrs now and I cannot seem to grasp some of these concepts so I was hoping someone here could clear a few things up for me. My first problem is detailed below... I have the following metric... d(x,y) = d(x,y)/(1 +...

Can someone explain to me how an atom can absorb the energy of an incident photon without being ionised? What is the photon energy transformed into and how is it transferred between the photon and the atom (what part of the atom absorbs the energy?). I can't find anything helpful online - the...

Dimensions of rectangle are a=2 and b=5. Perimeter and area P=2a+2b=14 and A=a*b=10 If we take a rope of length l=14m, encircle the rectangle and connect the ends we will have the same perimeter. Now we take this rope and make circle of it, this circle will have the same perimeter of...

Facts • Speed of light = 300,000 km/sec o http://en.wikipedia.org/wiki/Speed_of_light • Furthest observed galaxy = 13 billion light years away o http://en.wikipedia.org/wiki/Speed_of_light • the Universe has a calculated age of 13.75 ± 0.11 billion years o...

I'm just wondering if someone can point me in the right direction here.. or maybe I'm just crazy lol. I'm a big coffee drinker. When I go out, I usually grab a coffee and walk around with it in hand. (mall's, convenience stores, book stores, subways and buses etc...) and as expected there is...

The data came from my lab involving friction between wooden block with metal weight on it and a metal table. The wooden block is moved from rest and the force is measured using a force meter and Logger pro. Homework Statement Force of peak static friction = 23.285N. Normal force is...

Homework Statement I decided to cram these two unrelated question into one post, because they are too small and I don't want to crowd the forum with my many little bitty questions. 1. log(base A) of B= 1/[log(base B) of A] because: if log(base B) of A=C, then B^C=A and so B=A^1/C...

So suppose in frame K at x_1 a photon is emmited and its absorbed at x_2= x_1+L so, the photon in K has traveled a total distance of L. Now suppose we have frame K' moving at some velocity Beta*c. Why is it that in K' the distance traveled by the photon is different than L if the speed of light...

Homework Statement the answer to this question [limit x->0- |x|] given to me by my instructor was -1. (by 0- i mean to say the left handed limit). i have been thinking for the last 15 minutes but could not understand it. i think the answer should be 0 because as we get closer to zero from...

So, I'm trying to self-teach myself Abstract Algebra, and this idea of cosets is killing me, and I'm not completely sure why. Basically, I think I understand the theory, but I'm having a hard time visualizing it. Does anyone know a basic example of a group that would have a different right...

Ok, so I sort of have an idea of what kinetic energy is but I'm still kind of confused. I'm confused mainly because of the equation. Every source I've gone to has just given me the equation EK=1/2mv^2 but none of the sources mentions where it came from or what it means It almost seems like...

All I know about the Double Slit Experiment is that some particles are shot at a pair of slits, and the particle apparently splits, goes through both slits, and interferes with itself, creating an interference pattern, but if the particles are observed, they collapse and give the results you'd...

When expressing exp(\frac{i\sigma\cdot \widehat{n}\phi}{2}) as a series expansion, why can we make the assumption that (\sigma\cdot \widehat{n})^{2}=I? Someone I asked on campus showed me this and I don't quite understand its implications (partly because I don't quite understand permutation...

If you have one pool ball sitting on a table, and you're told to multiply the pool ball by negative one, how can it make sense that you're left with no ball on the table and also now lacking a pool ball? It seems more like it would result in zero. Note: This is just an idea myself and a few...

Explanation of a "simple" exponent rule in a derivative problem needed After differentiation, I get this : 9(t-2/2t+1)8 * 5/(2t+1)2 Now this simplifies into 45(t-2)/(2t+1)10 Now, I am wondering what the property is that combines the exponent from the top with the bottom to get an power of...

logic gates perform the logic operation but how. please explain an AND and nor gate circuit realization from diodes.

Supposing V is a normed vector space, the p-norm of {\bf x} \in V is: \lVert {\bf x} \rVert_p := \left(\sum_{i=1}^n |x|^p \right)^{\frac{1}{p}} There are 3 special cases: p= 2: Euclidean distance - 'as the crow flies' p = 1: Taxicab distance - sum the absolute value of components...

i am looking for a why. not a description of how to calculate or how to find its direction. i came across this question in a school question. "why does the wire move up" and then i thought. is there really a 'why'? or it just happens?

Hello friends, I am finding it a bit difficult to comprehend what the author of a famous textbook has written about TV signal band width. Here is the excerpt from his book. Could any of you please explain what exactly he means? I don’t get why the required bandwidth is around 5.5 MHz...

Hi all PF members! I've been bothered for many years by Panic attacks. It started when I was 15 and now I'm 17. Personally for me, the attacks occurs at evening and night but are common at the day, the attacks contains: intense death anxiety and hallucination. I've read about it and it seems...

Evaluate integral sqrt(9-x^2)/x dx I get to here -3 ln|csc(sin^-1(x/2)+cot(sin^-1(x/3))|+3cos(sin^-1(x/3)+c I plugged in for theta because originally I had this -3 ln|csc(theta)+cot(theta)|+3cos(theta)+c and I set x equal to a expression x=3sin(theta) Hence i had to...

What is the best explanation for why entropy must increase BY LAW. I can see it as being a good general rule, but I don't quite see why it's law, especially when you consider a micro-state explanation of entropy. What is the best argument for the law of increasing entropy?

2 problems, I need to use the direct comparison test with either a p series or a geometric series 1)series of j^2/(j^3 +4j +3) I thought of comparing it to j^2/J^3 which comes out to 1/j, but that dosent work, my teachers answer is you compare it to 1/5j 2) series of sqrt(q)/(q+2) I would...

Hi- I recently read Brian Greene's Fabric of the Cosmos which led me to think of an interesting concept that I would appreciate further explanation on. On page 456 Greene describes how in the multiverse view, if you traveled back to the past, you would have gone back to a past in a parallel...

I have to do an essay for a composition class where we explain something "I don't quite know everything about but feel as though I have a firm grasp of" and I was originally planning to do an analysis of sorts of a post-modern literary work but my professor thought it would be more in line with...

Strange sequences of events seem to happen to all of us at one time or another, more specifically events that are highly unlikely to occur in the same sequence. For example, one thinks of a particular scene of a television show or movie; the individual turns on his or her TV moments later and...

Hi PF I was wondering about the problem of quantum gravity, and maybe the reason why we struggle so much with a formulation of quantum gravity is, that spacetime itself is the source to all quantum phenomena. The evidence is, that with the standard model, we describe the quantum phenomena...

Hi, I'm doing MD-simulations in a capacitor-like system: 2 charged electrodes with a dense ionic liquid in between (non-diluted) with periodic boundaries in 2 dimensions (so for the electrodes I get infinite planes (xy) ,charged). I want to get the potential U(z) along the z-axis (witch is...

From an online book where the author tries to discredit GR, there's a part where he talks about forgetting about the rubber sheet analogy and just remembering: "A body moves along the path that makes time dilation a minimum." Then he presents a diagram and a little argument that is really...

Can someone please explain to me the motivation for these definitions of the cross product? Let A = (a1, a2, a3), B = (b1, b2, b3). Let A and B be the magnitudes of A and B, respectively, and let \theta be the angle between the vectors. A X B = AB sin(\theta) A X B = (a2b3 - a3b2, a3b1...

Homework Statement Half-Passage: In the packing industry, processing packages via conveyor belts is immensely practical and vital for operations. Maintaining packages in a neat and file line is no easy task, considering that many conveyor belts are non-linear and require the traversal of hills...