Weird Definition and 469 Threads

*Thread title was supposed to include the word "views" after "political." Anyway, I know that some jobs available to physicists require at least some level of security clearance and I am somewhat worried that my political views may hurt my ability to qualify. I was born and raised in the U.S...

In a Griffith's book (page 15-16) an author derives a momentum operator. In the derivation he states that he used a integration by parts two times. He starts with this equation which i do understand how to get to. $$ \begin{split} \frac{d \langle x \rangle}{dt} = -\frac{i\hbar}{2m}...

find the max value of xy (done in a "weird" way) Homework Statement so our teacher assigned this homework in the last 10 minutes we haven't read the function with 2 variables and I've never seen/used one (things were just getting in my head since it's only 10 mins i don't know if I'm making...

The Mystery Machine travels 55 mph down the highway of life. An innkeeper is standing 500 ft from the highway. How fast is the distance between the innkeeper and the Mystery Machine increasing 1 min later? The answer says it is 54.71 mph. I got something a bit more than 60 for the mph...

Hi, I'm trying to solve this equation inside of Maple: http://screencast.com/t/EeqzLhxS for gamma(s) I assign variables to each of the values like this:http://screencast.com/t/DBLS8BH6R When I try to solve I get this weird answer with a new _z variable...

Homework Statement A particle with mass m which can move only in one dimension, is subject to a constant force F= \begin{cases}-F_{0} && x>0\\F_{0} && x<0\end{cases} with F_{0}>0. First I've got to say if there is a potential energy. Then i must solve the particle dynamics (i.e. find v(t)...

Why does it write all that stuff about fxy2? Isn't it unnecessary? I mean, isn't the following true? If in a point (a,b): fx=fy=0 and fxxfyy>0, then the partial derivatives must be either both negative or positive, and thus point (a,b) is a local minima or maxima. And if fxxfyy<0 => (a,b) is a...

Homework Statement Solve the following differential equation, with the initial-value y(2)=2. y' = \sqrt{ \frac{1-y^{2} } { 1-x^{2} } } Homework Equations The Attempt at a Solution This is a strange ODE. It is continuous when either both |x|<1 and |y|<1 or when both |x|>1 and |y|>1. (Both of...

everyone knows, there exists the relation between the group velocity and energy dispersion. a question is how to expression the relation between the velocity and momentum k? it seems that the Dirac electron in graphene is massless.

I programmed a function that outputted this weird answer that looks like: ans = 1.0e+147 * Columns 1 through 16 0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0000 Columns...

So I'm looking for the reaction forces at the left end of the truss before I solve for the forces in the members of the truss in terms of F and theta. I summed forces in the x, y direction, took moments about point A,B, to get 4 equations in 4 unknowns (Ax, Ay, Bx, By). However, although Ax,Bx...

(This is a bit weird for a physics forum but whatever) I am arachnophobic (I can't even look at pictures of spiders). However that is not the point of this post. I have another weird sort of "phobia". I say "phobia" because it is not nearly as severe as my arachnophobia and when this happens...

Weird!? About the direction of rotation of wheels Suppose we consider a car moving on rough road in forward direction, wheels rotating clockwise. Since wheels rotate clockwisely they will push road backwards so friction acts forwards i.e. in direction of motion of car.The car will move...

Hi, so I was going over my lectures notes and I was looking at the Invariance, S2 for space time. I was just wondering why they call it time-like for S2<0 and space-like for S2>0 because, S2>0 says that there is an inertial frame where events occur at the same time (this has to do with...

Hi there, I'm new here, thought I'd share something that happened to me last night, I'm not sure if it means anything, but either way here goes. So I went to bed last night and starting dreaming, it was quite a long and vivid dream and at no time I consciously knew I was dreaming -- until a...

Sorry for this weird thread. Say that you throw a perfectly round 10 lb stone rock using a machine with constant force and distance of propulsion. Can a 10 lb ("average") human head,with full hair about 2 inches long, be thrown -using the same machine - just as far as the 10 lb rock...

Hi, in the book "Applied analysis by Hilbert space method", I have no idea what is happening in the last step here: <L(f), g>=\int^{1}_{0} L(f)\overline{g}dx=-\int^{1}_{0} f''\overline{g}dx=-\int^{1}_{0}\overline{g} d(f') where L(f) = -f'' and both f and g are functions of x. It...

This is very weird, but I found an inconsistency in the application of Cramer's Rule for a 3x3 simple linear matrix. 1x + 1y + 0z = 3 -1x + 3y + 4z = -3 0x + 4y + 3z = 2 Dz = 1 1 3 -1 3 -3 0 4 2 If you take the determinant across the first row To find Dz, I constantly get...

Homework Statement This question is about finding the smallest bowl to contain all the water being spurt out of a water spray head. They used the lagrange multipliers to solve it which I understand, but the the envelope doesn't look like a parabola to me?? Isn't the envelope...

6pq+r=\sqrt{r^2-4ps}, \ \ p\neq 0 \ \ (1) Without squaring (1) or any of it's rearrangements, express p in terms of only q, r and s.I realized this is some sort of quadratic formula so I got p = \dfrac{-r+\sqrt{r^2-4ps}}{6q} so for the quadratic ap^2 + bp + c, a = 3q, b = r, c = s, 3qp^2 +...

xy''+y'=-x y(1)=0, y(0) bounded (so the natural log, 1/x etc. terms drop out) homogeneous, cauchy euler: y=a+bx variation of parameters, and using the conditions gives y=1-x, I think (i tried this previously and I think this is what I got, I didnt write it down). Very different from what I...

http://en.wikipedia.org/wiki/Four-force At the bottom of that page, the author provides the generalization of four force in general relativity, where the partial derivative is replaced with the covariant derivative. However if you notice on the second term in the third equality, there is a...

Hi all! First off: I don't know which forum to post this. I'm no grad student or PHD so academic forum seemed wrong, and it's not really just math, since it was the result of a measurment and the signals can come from environment, etc. Ok. I measured the magnetic field using a sensor...

Hello, I was in the processing of depositing BST thin films on Platinized Silicon substrate from solution using spin casting. Six layers were deposited. Each deposition was followed by 400 celsius for seven minutes and 700 celsius for three minutes. The final film was annealed for an hour at...

It is written in my book under the sub-heading Nuclear Fusion... "If we take some light nuclei and force them to join together, the mass of the new HEAVIER nucleus will be LESS than the consistuent parts, as some mass is converted into energy... This is completely contradicting... Is it actually...

Hello to the community! My question is really silly, i really don't know much of physics and radiation thing, but as i was watching the Hulk movie, Bruce got affected by radiation gamma and he became that big humanoid thing who called Hulk, my question is, what can radiation gamma really do...

Weird double integral. Please help! its from thermodynamics...but i don't think you really need to understand thermodynamics to figure out what math trick they used to get from the first integral to the second integral http://img833.imageshack.us/img833/833/intek.png i have been looking...

Suppose that, while lying on a beach near the equator watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears. You then stand, elevating your eyes by a height H = 1.70 m, and stop the watch when the top of the Sun again disappears. If the elapsed time...

I ran into a kind of strange thing today while coding. I needed Pi in a program, so I used 2*accos(0.0) to pull it out, but my answers were slightly off. I checked the Pi calculated and it was off after a few decimal places. "Odd", I thought, and just decided to put in Pi as an assigned number...

Suppose I know my function G is infinitely differentiable on the closed interval [a,b] and that all derivatives of G (including G itself) vanish at b. For any z in [a,b], I have by the FTC that \int_z^b G'(w) dw = G(b) - G(z). Or, switching limits, \int_b^z G'(w) dw = G(z) - G(b). One...

Well I personally love the "Pillars of Creation" because they are magnificent. I was scanning one picture and i saw what look very close to a face and i thought i would like to share it. Picture 1: "Pillars of Creation" Picture 2: Face cropped out.

You may have heard it said that the largest organ in the human body is the skin. This weird creature seems to consist exclusively of that organ. Skip forward to about 1:30 for the best view of it: https://www.youtube.com/watch?v=-E-8_wDgN7c

Hello everyone! A little background story here. I am 19 in jc. Had many health problems my junior and senior year in high school (4 surgeries) and this caused me to be very lazy with my school work. I basically bs'd my way through algebra 2, had a terrible chemistry teacher, and bs'd my way...

Homework Statement A(\vec{x}) = (F + T * x )2 F is a constant, x is a 2×1 vector T is a (constant) 1×2 matrixB(\vec{x}) = || K.Z.x ||2 k:3\times3 matrix and Z:3\times2, x the same as aboveB(x) is also R2→RC(x) = A(x) + B(x) Homework Equations 1- I am confused...

I am doing a senior design project regarding water hydration and did some tests to get a general evaporation rate. I assumed that evaporation is proportional to the surface area of the water to air boundary so I thought that the water level of water in any constant cross section container should...

Homework Statement We have a infinite plate on the yz plane from x=-d/2 to x=d/2. The plate has a uniform volume charge distribution ρ_{0}. Parallel to the z axis at y=y_{0} we have a cylindrical hole with a radius a. At the center of the hole (paralle to the z-axis) we have an infinite line...

Hello all, I have been having a really strange problem lately on my TI-84. Whenever I graph anything, there is always another graph which appears as a stretched parabola that spans the first and fourth quadrant. It is annoying because I cannot view certain parts of the graph I want to. Anyone...

Parallel universes...Multiverses...Something created out of Nothing...etc...A case could be made that all these theories are weird, if not lunatic, & unprovable. Why then cosmologists readily accept to discuss them, but reject the concept of a "superior will" behind all existence - God - as if...

Hi everyone, I'm taking an online "Driver Safety" course and came across this gem: "Here is an example of how disastrous the force of impact can be: If you weigh 100 pounds, are traveling at 30 mph, and hit a stationary object, the force of impact is 3000 pounds (mass multiplied by...

So I'm trying to check the moment of inertia Ix for this weird I beam. The three steel plates' moments of inertia were easy enough to calculate. However, I would appreciate any help on how I should go about calculating the contribution of the four L6x6x1 angles to the total moment of inertia...

I did a simple dissolution reaction (potassium nitrate + water), and measured the solubility at different temperatures. I did a graph of ln K (y) vs 1/T (x), where K is the rate constant, and T is absolute temperature. Following the lab experiment instructions, where it says the slope is...

I have $u_{tt}=u_{xx},$ $x\in\mathbb R,$ $t>0,$ $u(x,0)=0$ and $u_t(x,0)=\chi_{[-1,1]}(x).$ What does mean the last condition? In such case, how to solve the equation then? Thanks!

This is not a HW question! THIS IS A DISCOVERY that I want to explore. I will explain it as follows: Suppose I have this exercise, where I know the static coeffecient between the beam and the floor is 0.3, whereas in the wall there is no friction. I want to find out if the beam slides, or...

So, I'm studying for my linear algebra midterm and I came up with kind of an interesting question that I pose to all of you brilliant people on physics forums. Let's say you have a linear transformation T(x)=Ax, with A being an nxm matrice. Apparently, for this equation to hold, x must be a...

Ok let a and b be non zero numbers (\frac{a}{b}) / (\frac{1}{0})=0 But shouldn't that be undefined since you would get a fraction like this \frac{1}{0} which isn't allowed. Since it got us to a "wrong" answer, that would mean our assumption was wrong. Please tell me where I went wrong.Not...

I need some brief update of how scientists are making any progress in coming up with theories explaining what matter is and how matter was formed. My latest memory on this one tells me everything is just a form of energy, there were singularities in the old universe, some kind of energetic...

For sin(4pi), my calculator gives -2^-13. Obviously, that is really close to the correct value of 0, but it just says 0 for ANY other multiple of pi I've tried. Weird right? TI-83 plus.. common calculator. Anyone have issues like this?

Homework Statement A mass m is attached to one end of a light rod of length l. The other end of the rod is pivoted so that the rod can swing in a plane. The pivot rotates in the same plane at angular velocity \omega in a circle of radius R. Show that this "pendulum" behaves like a simple...

One day I just put on my [SIZE="5"]polarized sunglasses, and on the road, I looked at cumulonimbus cloud probably in the congestus stage in a system with many other cumulus clouds (those big puffy clouds), and a single giant cumulus cloud appeared yellow-ish when wearing the polarized sunglass...

Homework Statement evaluate Homework Equations The Attempt at a Solution i don't think there is an elementary function as anti derivative for this integral i tried taylor expansion, doesn't seem to work. Can anyone give me a hint ?