Strange Definition and 588 Threads

Homework Statement A particle of mass 1[kg] is moving with a velocity of: \vec{V}=2 \hat{x}+ \hat{y} -4 \hat{z} [m/s] . At the instant t=0, the particle experiences a force which is given by: \vec{F}= \vec{A} \times \vec{V} - (\vec{A} \cdot \vec{V}) \hat {A} where \vec{A}= \hat{x} -6...

The equation of linear thermal expansion is l=l_0\left[1 + \alpha(t - t_0)\right] (it is similar also to the equation of resistivity, \rho=\rho_0\left[1 + \alpha(t - t_0)\right]) \alpha is a constant dependent only on the material we are speaking about. Now, let's say I have a bar 100 m long...

The following question, although probably sounding inappropriate for this forum, is actually very important to me. The easy answer to the question is, “It can’t be done.” But a great deal of learning and increased understanding could be gained if the answer were, “It could be done if...”...

Surge Protector -- strange reaction to light sources? We have 2 power strips in our home in which the indicator lights both react to a light source in the following manner: during the day (in the presence of sunlight) the indicator lights shine red with a small flicker every now and then. In...

how this function f(x)= 0^{-x} should be understood? , if x is NEGATIVE, we find no problems, since 0 raised to any power is 0 but how about x being a positive real number ? , or x being a PURE COMPLEX or complex number ? could we consider a 'regularization' to this f(x) so...

Homework Statement I'm trying to compute something of the form \langle \int_a^b{f(x) dx} \int_a^b{f(x)^{\dagger}dx} \rangle where the dagger means complex conjugate and the brackets are ensemble average (f(x) is a statistical quantity). I'm supposed to use the relation that \langle f(x)...

Homework Statement lim(x→∞)(lnx)^2/x Homework Equations The Attempt at a Solution Since lim(x→∞)(lnx )^2=∞ and lim(x→∞)x=∞, the function is indeterminate, ∞/∞. lim(x→∞)(lnx)^2/x=lim(x→∞) d/dx (lnx )^2/(d/dx x)=lim(x→∞)(2 lnx (1/x))/1 An I am stuck...

My stereo remote has begun exhibiting strange behaviour. If I use the Power button to turn it on (or off), it will continue to do so for as much as 30 seconds. i.e.: - I point the remote at the stereo and press Power, stereo turns on (the on/off cycle on my stereo takes a good 4-5 seconds)...

Homework Statement a ball of 2kg falls from rest froma 5m height and collides elastically with the floor below. what is the magnitude change in the object's momentum? Homework Equations The Attempt at a Solution I did S=So+.5aT^2 I solved for the time it takes to reach the...

Hi everyone! I'm running and modifying some code from the Alejandro Garcia book, "Numerical Methods for Physics". I generalized it to three dimensions, but noticed a problem when calculating the average temperature. Then I went back to the original, untouched program, and found that the problem...

So, I was reading the book "Riemann's Zeta Function", by H.M. Edwards, and on page 10 I see an integral I don't quite understand. Here's the integral: \int_{+\infty}^{+\infty} \frac{\left(-x\right)^s}{e^x - 1} \frac{dx}{x} My first problem with this is that, I see an integral from some...

Homework Statement If f(x) is equal to... x+9 if x<-3 -2x if |x|\leq 3 -6 if x > 32. The attempt at a solution The first and third "segments" of when the function is defined as being x+9 and -6 are pretty straightforward to me, however I am unaware of the significance of the placement of the...

hello every body I 'm very happy to be with you ..,I think that is my first topic last day , our teacher of physics tell us a new and a strange information , he say: " if we go out of Earth's atmosphere , we Will not see anything! , we see just black color ! " and he Tell us that a...

Hi, Homework Statement I was given a linear equation system of the form Ax=b where x=(x, y, z, w), I reduced (A|b) to its canonical form which is this: Homework Equations The Attempt at a Solution At first I thought that this means that there is an infinite number of...

please is there a topic that discuss with illustration factor that causes Strange behavior of the density of the water around the freezing point

Homework Statement A man of mass 50kg is riding a horse of mass 450kg at a steady speed of 10m/s. The horse stops suddenly and the man is thrown forwards. Find the speed with which the man is thrown forwards. Applying law of conservation of momentum, the resulting speed is 100m/s. Poor...

Does anyone share the same strange feeling I have about the Standard Model? The feeling that it had almost failed… So, let me present you Standard Model: 3 generations, 2 types of particles (quarks and leptons), dividing into 2 subtypes (upper/lower, lepton/neutrino), giving 12 fermions, or...

The following curve is geodesic in Schwardschild metric: \tau \mapsto [(1-2m/r_0)^{-1/2}\tau,r_0,0,0]. The tangent vector is: [(1-2m/r_0)^{-1/2},0,0,0] , its length is 1 and its product with killing vector \partial_t is equal: (1-2m/r_0)^{1/2} = \textrm{const}. So the body lays at rest...

heeello friends!;] i have book "wstęp do współczesnej geometrii różniczkowej" written by Konstanty Radziszewski, this title in english mean something like... "basics of modern differential geometry", and here are many formulas which look similar to one another, but I never know what it means and...

Sometime when I'm tired, I'd rather make hand gestures (like an instinct in me) than opening my mouth and pronouncing sounds/intelligible words. I wonder which of the 2 requires more energy to our body. As I read that swinging our arms when walking costs us 10% energy less than non swinging...

I have 3 sensors I know the distance between. They report to me 0.58V when no change is found and when a change is found they report .64V .79V .66V for example. Would it be possible to locate the point where the item is?

When I was like 10, a painful lumb developed in my ear lob... and it grew quite a bit (not to bad). It hurt for a few months and the suddenly stopped hurting. Never told anyone, but it stayed there, for six years and SLOWLY shrank... Now I am 16 and it is growing again and it hurts once...

is this actually a prototype? the photo seems real...

http://www.examiner.com/x-5182-Dallas-Weather-Examiner~y2009m12d10-Solar-systems-greatest-mystery-at-Saturns-north-pole If anyone here knows a lot about astronomy, and astro-physics, could you please try to scientifically explain this? The same shape appeared on Jupiter about a year ago...

Please have a look: http://www.thesun.co.uk/sol/homepage/news/2764647/Spiral-UFO-puts-Norway-in-a-spin.html It's strange isn't it? Anyone have an explanation? Could it be man made?

Could be an asteroid or comet - the spiral thing is pretty cool.

I am looking at fan curves here at work and I stumbled upon this one. Its for an 80mm diameter tube axial fan. What's up with the Flowrate vs RPM curve (the dashed line)? In the flowrate interval between 12 - 23 CFM there are instances of the same RPM for different flowrates. That...

HP strange RPN operation? I just find an odd behavior on my hp rpn operation. Can someone try the following sequence of entry and explain to me this strange behavior? Press 5 (any number will do). Press 'Enter' (this should duplicate 5 to x an y stacks) Press 'Enter' again (duplicate 5 again...

Hi there, I became really serious studying the basic principles of physics few months ago. There is a plenty of good study material out there, so there was no need to ask anybody anything. Until now. The problem is with the speed of light c and why it has properties and value it has. Few...

http://www.cidrap.umn.edu/cidrap/content/influenza/swineflu/news/oct3009ukraine.html First the west nile virus, then SARS, bird flu, then the swine flu, and now this strange virus. It seems that there is a new type of deadly disease popping up somewhere in the world every few years. More so in...

Hi! What is your opinion about this article: [PLAIN]"www.bme.hu/ptee2000/papers/fetea.pdf"[/URL]

Homework Statement f(t)=\frac{t^5 + t^6 - 1}{t^7} Homework Equations The Attempt at a Solution This is different than the other problems I've been doing. My first guess would be that I would do this: f(t)=\frac{5t^4 + 6t^5}{7t^6} Is that the final answer or is there another...

At least that is what I am told when I ask it around here... How long would it take to go get to 45 miles per second at human tolerable acceleration? I am not a math whiz obviously, but I have some questions that get me some really strange looks, and no answers. I know that currently...

To calculate the centroid of a cone, it seems that you have to use calculus. It comes out to be h/4, where h is the height from the base of the cone. But intuitively I thought that the centroid would have been h/3 because that's a triangle's centroid, and the cone can be obtained by rotating a...

a strange solution ? I was solving a tangent problem and came across a strange thing , its a simple quadratic equation ,y2 - 4y -8 = 0 , by quadratic formula , y = 2 + 2*31/2 and 2 - 2*31/2 , now if i write the same quadratic as (y-2)2 = 12 , then i apply square root function on both...

Is this real stuff? My first reaction was that that must be fake. Somebody just composed some sounds effects, and is making fun of astronomy. I didn't succeed in finding any debunking for that though, from the internet, yet. Then I found this NASA site...

Homework Statement I need to find the limit of the sequence: [(1+1/n)(1+2/n)(1+3/n)...(1+n/n)]^(1/n) as n approaches infinity. I know that the limit should come out to 4/e, but I cannot figure out why. Homework Equations None. The Attempt at a Solution The original sequence...

Suppose U and V are finite-dimensional subspaces of some finite-dimensional space W (over the field Q in my actual case, but probably irrelevant) I've got a subspace in mind that I can't quite define well. I'll start with a concrete example: Consider R^3 with orthonormal basis {x, y, z}. Let U...

Homework Statement We had to basically modify a few variables in the given code and then shoot it out with a valid output. I decided to have some fun with it. However I get a strange syntax error, here is the code: //Conditionals controlling the cookie response output if(cookies...

Hi all, I'm producing one of my first proper TeX documents and getting a strange effect. A couple of my equations have the equation numbers stuffed onto the end of the equation virtually adjacent to it, rather than on the right hand side aligned with all the other labels. Any ideas why? I think...

Okay, if we have a parallel plate and we force a negative charge to the negative plate and a positive charge to the positive plate (both having the same charge) and release them both at the same time, how do we calculate the current?

Having discovered up, down, strange, charm and bottom quarks, why did scientists undertake similar experiments using higher and higher energies?

I have found some papers about strange observations in the Earth gravity during total solar eclipses. There is a very small difference (~10^-9) but there is a differnce (see the attachment). Is there the possibility to be a new gravity phenomenon? I think that it can be an atmospheric...

I'm trying to solve the following problem (not homework :smile:) which is a strange form of diagonalization problem. Standard references and papers didn't turn up anything for me. Does anyone see possible approach for this? - Given n x n full rank random matrices A1, A2, ... A9 Find length...

Hi, I've just read Feynman's book:'QED:The strange theory of light and matter' and, in order to measure the probability that a photon will reflect or transmit through a partially reflective piece of glass, Feynman introduces an 'imaginary stopwatch'. Can you explain me: -what do the hands of...

I was doing a practical to analyse for my school assessment with regard to Planck's constant. I was using a Planck's constant kit to get some results but the results I was getting was inconsistent with my research as seen below. Isn't the voltage meant to increase as the wavelength is shorter...

Since I'm around that old question about an observed phenomenon came to my mind: - a cup is filled with water and heated up using a microwave oven. When I see it starting to boil, the oven is stopped abruptly. And while there is no more energy injected into the water, it boils even more for a...

Right this is a question about some radio noise that I picked up from my speakers last night. My speakers were plugged into my tv with the volume off, this tv was plugged into a Freeview box which had an aerial cable plugged into that connects to the aerial in the loft. Just after I...

In the UK they have a reality show where they pick real people that dress as freaks and show them what they would look like as normal human beings. It's called snog, marry, avoid. Here is a link to one of the "make overs". I can't believe this person actually dressed like that. Believe it...

Hi, Last night my girlfriend and I were lying in bed talking. We were facing each other and our faces were about 1m apart. The room was dark. Suddenly we both jumped because we experienced a very short lived but bright flash of white light that seemed to emanate from a point about 50cm above...