Interesting Definition and 790 Threads

Homework Statement Find the acceleration of the system. Friction constant of incline is 0.2 Homework Equations Force of friction = 0.2 * 7 * 9.8 * cos30 = 11.88N Force of gravity pulling down 7kg weight = 7 * 9.8 * sin30 = 34.3N Force of gravity pulling down 4kg weight = 4 *...

Hey, my problem is that I really want to flirt with girls and have dates badly. However, when approaching a girls, I feel that I have no plan. If I start a conversation anyway, it might sometimes go OK in like the first 20 seconds, but then I end up not really knowing what to say. I know...

Find the area of the shaded region if r = 1/4 and each side of the square is 1. I know the solution can involve similar right triangles and systems of equations, but if I remember correctly this was a pretty messy way to do it. Anyone have a simple (or more complicated) solution? You can...

This is not a bookquestion by far. It does have a nice solution, but I am stumpled on how to get it \int_{0}^{\infty} 1 - x \, \sin \left( \frac{1}{x} \right) \, \text{dx} Now I could split the integrals into two pieces, where the first part obviously goes towards infinity. The second...

I just finished my second year of Engineering Physics at McMaster (specifically, nuclear) and I'm on a summer coop term now, but I'm looking for something fun to do after work and on weekends. Does anyone have some fun, interesting project ideas? I've got some experience with analog and digital...

Hi, Do someone have a clue on how to answer that? : An anomalous bright red spectral emission line has been detected in the nearby solar-type star GL1023. The brightness of the feature sometimes suddenly changes by a factor 2 with a frequency of 0.92Hz. After about 10 min of these...

Homework Statement Consider a translating and rotating rigid disk. As it movies, it just tips the top of a rod that is initially at rest. The puck sticks to the rod, forming a rigid body that looks like a popsicle that after the collision moves on as one rigid body. I did the calculations to...

Homework Statement The problem can be found here. http://wopho.org/dl.php?id=17&dirfile=selection-problem/helical_rope.pdf" I am attempting to solve part 3. Homework Equations The Lagrangian of the system is: L= \frac{m\dot{x}^2}{2}+\frac{mr^2\dot{\theta}^2}{2}-k \left(...

Homework Statement Consider the picture below. The picture below shows an infinitely long cylindrical line of charge with charge density per unit length +\lambda and it is located at the center of a non-conducting cylindrical shell with an infinite length and has a charge density per unit...

Hi Guys, What are the milled indices of plane (see attached figure). Its very interesting...and I am receiving every-time different answer from others. Have a look. Shriphy

Homework Statement If you could hypothetically experience 1 femtosecond (1E-15 s) the same way you do normally for 1 second, how long would it seem to experience 7.078E-4 seconds? Homework Equations note: 1 femtosecond is to 1 second, what 1 second is to 31.7 million years. The...

Homework Statement http://img687.imageshack.us/img687/9065/matrixk.th.png Uploaded with ImageShack.usThe Attempt at a Solution Alright, here is how I did it. First I need to find my eigenvalues \begin{bmatrix} 0-\lambda & 1&2 \\ 0& 3-\lambda& a\\ 0 & 0 &0 -\lambda \end{bmatrix} So...

Hello, I am faced with a perplexing challenge in analyzing my results for an ecology experiment. All help is immensely appreciated. The situation: I have 6-month longitudinal mass data for 8 hummingbirds. From eye-balling the data, time definitely has an effect: masses tend to decrease...

Interesting physics relative velocity problem with some trigonometry mixed in. Homework Statement Agent 007 has just stolen some blueprints from Dr. No, whose henchmen are now in vigorous pursuit of Mr. Bond. He sees his best chance of escape: a wooden boxcar. In a moment, James is in...

I find these problems difficult anybody want to help me out?

So today I noticed something pretty weird on an exit sign above a door in my school, looking somewhat like this: http://www.examiner.com/images/blog/wysiwyg/image/exit_sign.jpg The effect is pretty difficult to describe by words, since I didnt expect to see anything like that on it. But it...

Check this out: Violation of a temporal Bell inequality for single spins in solid by over 50 standard deviations, G. Waldherr, P. Neumann, S. F. Huelga, F. Jelezko, and J. Wrachtrup (2011) "Quantum non-locality has been experimentally investigated by testing different forms of Bell's...

Are they allowed? (funny ones didn't last long) of PF members also?

when a material becomes charged due to static electricity how come it does not stay charged or how come the atoms of the material do not become ions

As some of you may know, I'll graduate next Spring with a B.S. Mathematics and Physics minor. From my perspective, I wanted to gain a broad and fundamental technical education in undergrad. I view grad school as career training. Applied math is an option at my university. It would be the easiest...

A general question I came up with and it might be trivial, but I'm not entirely sure what the answer is. Does there exist a function analytic in the upperhalf plane that is unbounded and all of its derivatives are bounded but not identically zero? or equivilently does d^n/(dz)^n(f)<M for...

Just looking for some links to sites with guidelines for a quick chemistry demonstration. No particular topic, just nothing overly simplistic. I'd like it to be "visually entertaining" though - it's being done as a presentation, and frankly I'm not sure that the most interesting...

I am studying orbitals at school. They are very interesting and strange at the same time; they seem to be very similar to a planet in orbit around a black hole. However I am not here for that. I was wondering if you knew a good and short reference in order to understand E,Shrodinger's equation...

Hi, I was wondering if someone might have some insight into this problem. It is not for school or coursework, just for fun. First I thought of a circle containing two smaller circles within it. The two smaller circles had half the radius of the larger circle and so their boundary touched each...

Imagine for a moment a steel core with no air gap, that is driven to saturation by a powerful permanent magnet. Imagine next that a coil is wrapped around some section of that core some distance away from the magnet, such that their only flux linking is through the saturated core. The magnet...

So basically I need to do a project on a topic in "beyond standard model" can anyone give me any theoretically interesting topics? I know this is a very loose question, but .. p.s I am a 3rd yr undergrad so nothing to crazy Only topics i can think of are just a standard search for a...

A conductive plate with no initial charge is put between two identical positevily charged plates. Is it possible that the plate which is put between those two plates configures a situation where the net force acting upon each plate is zero? (the third plate could have different dimensions then...

I want to find a function describing the motion of the particle undergoing the type of motion depicted. Basically it is a particle on a rotating vane (constant angular speed) and at some time it is released. The particle will move along the edge to the tip of the vane (and eventually fall off)...

(AB+1)/(ABC+A+C)=0.138, Find values of A,B,C.

Hello,I just discover a interesting phenomenon at lunch time when I drink a glass of water: When I hold a glass in my hands, If I look from above at the innerwalls of the glass, we can see a very bright and clear image of patterns on your fingertips through the glass. But when I use...

Harvard professor of history Niall Ferguson gave an interesting talk on history at the Australia Center for Independent Studies http://fora.tv/2010/07/28/Niall_Ferguson_Empires_on_the_Edge_of_Chaos His main point was that empires die fast.

I've got to do a talk for part of my physics degree and I'm trying to think of subject ideas. It doesn't have to be physics exactly, but must be scientific in some way. I was wondering if anyone had any ideas for quirky subject matter. To give you an idea, my favourite talk from the year...

So I'm really interested in the field of wave optics, and luckily for my undergraduate program, we get to do a measurement project on any area of our choosing. I was looking up topics and there are some interesting ones such as the luminous fountain where they use the idea of fiber optics to...

Hey all, I am currently looking to build something for fun, and to add to my college application/resume. I was thinking about building a particle accelerator, and did a good amount of research into that, and it seems like it would be expensive and complicated. However, I am still open to that...

What spacetimes do you consider to be important or interesting? Important or interesting as solutions to the Einstein field equation, or important or interesting geometrically. I'll start the list. Minkowski Schwarzschild (including extended) Kerr(-Newman)...

So I was trying to sleep last night but I had a random thought of a function that would be very very painful to graph. I am currently out of town and don't have access to a graphing calculator. Plus I kinda wanted a logical answer before seeing the graph to it. Perhaps some of you have seen it...

I was checking out a developing blizzard forecast for the northeast US today when I saw this interesting fog feature over the South Dakota, Nebraska, Oklahoma area. http://www.weather.com/maps/maptype/currentweatherusnational/uscurrentweather_large.html EDIT: The image is changing. It was the...

He once had a difficult moment, just to see what it was like. https://www.youtube.com/watch?v=L-4zfsy6rsM What else can be said about the most interesting man in the world? Stay thirsty my friends.

What does everyone think about this? http://www.fordham.edu/academics/programs_at_fordham_/mathematics_departme/what_math/index.asp

For the sake of doing it, I'm trying to factor a quintic polynomial over the reals using a cool technique I found a few days ago. It involves stenciling out the general form of the expression you want and then solving a nonlinear system in which there are more variables than there are...

Homework Statement A power station has a huge tank to store water. The tank is filled by a pump which is attached horizontally to the bottom edge (the bottom of one of the walls) of the tank. In the floor of the tank is an outflow valve. The valve is subject to huge forces and after some years...

Hi, I'm trying to understand spinors better, and I seem to be getting stuck on understanding the reason they're said to transform differently from vectors, and I'd appreciate any help with a justification for that. I'm sure I'm missing something pretty simple, but here goes; Here's what I've...

I just realized a Van de Graaf generator around 400...500 kV might be easily doable, by an average amateur working in a garage. I was also thinking these days about a DYI cyclotron project, which I scrapped because the magnet is just too hard to make and feed. But then I figured the Van de...

Homework Statement points A and B are on the parabola f(x)=4xsquared + 7x-1, and the origin is the midpoint of AB, find the length of AB Homework Equations The Attempt at a Solution I have spent time drawing out graphs and such but I am totally lost as to where to begin

I plan to take Engineering as a second degree since I haven't had much luck with my BSc. I'm considering Biomedical (somewhat high paid but jobs are seem to be rare), Chemical (twice as many employed and slightly higher pay) or Mechanical Engineering (highest number employed by a long shot). I...

This just hit me: there is a high probability my family and I will be alive to witness several key events in human history. Just think about it: there are at least 10,000 years of recorded human history but only in the last 150 of those people have experienced the most amazing things any human...

I was thinking about how big the universe got after inflation occured. Then I thought about Hubble's parameter. Ho = V / d (At the big bang, the distance between the two edges of the universe were zero) Ho = V / 0 Ho = ∞ km*mpc / s Therefore, the rate of the expansion must have been...

I request you all to perform this activity now (it will take less than a minute)- 1)Take a rectangular piece of paper. 2)Make two holes of the size or your fore-finger in it - equidistant from the edges (refer the figure attached. 3)Insert the fore-fingers of your two hands in the holes...

Homework Statement Prove or dispove T:R^n \rightarrow R^n is a linear transformation if for every u \in R^n and for every v \in kerT , T(u) \cdot v=0 then KerT = (ImT)^{\perp}The Attempt at a Solution True. since it was given T(u) \cdot v=0 and we are dealing with all of R^n then...

Homework Statement lim (x,y)→(3,1) | (x2y - 6xy - x2 + 6x - 9y - 9) / ( (x-3)4 + (y-1)2 ) Homework Equations none The Attempt at a Solution Since we have the indeterminate form '0/0' when we simply substitute (x, y) = (3, 1) we need to show the limit Does Not Exist. we will show...