Interesting Definition and 790 Threads

I found an interesting rock in a river bed in Arizona once. I think this rock would prove that the Earth is much more than 10,000 years old as creationists like to believe. It was a piece of conglomerate. It had been rounded in the river bed, about 10" across. The interesting thing was that it...

So I had a student today ask me if I could come up with a simple 2 dimensional area problem. I was like -sure what is it. The question was: If a cow were strapped to a tether outside a 10' by 10' square barn, at the corner of a small outlet door, and had a 100' leash/tether, what would the...

Hello All, Was thinking about some of the basic concepts of magnetic induction, in the case of a stationary solenoid coil with a moving magnet crossing the face of the coil. We know that when the magnet approaches the face of the coil and the field increases, that a votlage potential (emf) is...

I have absolutely no physics experience but decided to take Physics C next year as a junior. Is this a good idea? I am a very math-oriented person and the questions that some people as on these forums interest me a lot. So, is physics really interesting? Or should i not take Physics C?

Hello all, I'm in the process of working on developing a course to prepare students for calculus. The emphasis is to build up students' conceptual mathematical thinking, particularly that related to the notion of the function. Recognizing that motivation is one of the biggest issues to...

Hi, I'm presenting a proof that e is transcendental, but I want to spice up the presentation a bit by exploring some interesting perspectives, such as connections to topology, abstract algebra etc. I've already selected the Lindemann–Weierstrass theorem as a possible candidate. Can you suggest...

Homework Statement Two satellites are launched at a distance R from a planet of negligible radius. (Yes, that's what the problem says...) Both satellites are launched in the tangential direction. the first satellite launches correctly at a speed v_0 and enters a circular orbit. The second...

"Think of what you're saying, you can get it wrong and still think that it's all right." from some song by John Lennon and Paul McCartney. anyway, this got me thinking about how many times I've though I've really understood something, or was absolutely sure that I was correct about...

I am picking courses for next semester and am torn between a numerical analysis class or one on Fourier series and wavelets. The n.a. course fits my schedule way better but every book and syllabus I have browsed concerning numerical analysis has seemed uninteresting--more like a branch of CS...

I've ecountered three interesting problems lately: 1. On a motionless sphere you can lay a cylinder. In what conndtions it is possible? After we move cylinder by a little degree it starts to vibrate and after a short period of time it goes back to the static situation. Why? 2. When mooring...

Apparently students were given an assignment to prove whether hell obeyed the laws of thermodynamics and if it was endothermic or exothermic. The most interesting response is given below. http://wfhummel.cnchost.com/hell.html author unkown.

I am trying to make a function which is exponential for a while, and then turns gaussian: f(l,d) = \lambda e^{-\lambda d} , 0 < d < l and f(l,d) = (1-\int_0^l \lambda e^{-\lambda d} dd) \frac{1}{\sigma \sqrt{2 \pi}} e^{-(d-l)^2/(2\sigma^2)} , l < d < \infty (That is supposed to be...

Hello here you have the same question in the enclosed What is the average value? average value for (exp \alphaZ ) = \int\int exp\alphaZ ds / \int\int ds Over the sphere S: X^2+Y^2+Z^2=a^2 Also by use the parameterization X= a sinϴ cos ɸ Y= a sinϴ sin ɸ Z= a cos ϴ...

So next semester I am studying one section of the Philosophy of Physics at Oxford. This is paid for through my college; thus I can only take 9-12 hours (I am going the third term which doesn't start until late April). I am already a little behind because I had trouble deciding and have three...

What do you think is some interesting or/and sensible way to define functions like exp(), cos() provided basic algebra rules (including integration) are known? I make a suggestion I came up with \ln x:=\int_1^x \frac{\mathrm{d}t}{t} from where key properties follow directly. For example \ln...

http://www.stumbleupon.com/toolbar/#url=http%2525253A//www.eigenfactor.org/map/maps.htm

Hi guys, I've been dropped in at the deep end at work, tasked with designing a latching mechanism for an armrest on a luxury aircraft seat - It has to work on a remote latch principle, ie by pushing a sprung-loaded button downwards to actuate a link arm via a pivot, which then retracts the...

I was having a debate with a friend about how to show the following limit. \lim_{n \to \infty} \cos( \frac{2 \pi}{2n - 2} )^n = 1 I claim that you can just hand-wavingly say that since cosine of 0 is 1, and 1^infinity is 1, the limit is 1. He claims I need to show this using some sort of...

Heres something i came across in a book but there's no solution... take two inspectors in a factory (they can't talk to each other), and they inspect a series of products and they deem them defective or not. So the results would be (D,N), (N,N) ... where each coordinate is each inpectors...

Homework Statement In class today my physics professor proposed this question and left it unanswered: (We're beginning to study Gauss' Law) "Lightning strikes Manhattan in a brilliant display, each strike delivering some 10,000 amperes of electron flow from the cloud base to the ground. How...

I went to the Uni of Birmingham open day this weekend gone, with the intention of finding more about both the Physics and the Mechanical Engineering degree programmes. Firstly, the Mechanical Engineering talk was disappointing. Mostly because the guy giving it was a bit of a dick. All he...

Hey everyone, I was given this fun little probability question from my tutor after I finished early in one of my classes about three weeks back, and I just can't seem to crack it! Something about gambling and probability makes my brain go haywire (or maybe its some other, deeper problem...

I was going to read the whole thing but it was a long article http://en.wikisource.org/wiki/Industrial_Society_and_Its_Future#The_.27bad.27_parts_of_technology_cannot_be_separated_from_the_.27good.27_parts Do you think much of what he said was true?

An interesting inequality--question on the proof... I am working on the following proof and have gotten about half way; If a_1, a_2, \ldots , a_n are positive real numbers then \sqrt[n]{a_1 \cdots a_n} \leq \frac{a_1+a_2+\ldots +a_n}{n} By induction, I started by showing it for n=2...

Probability gets interesting? Hey guys thought this was an interesting problem that our lecturer purposed: Pick any word in the first few lines and do the following: Let’s say your choice is the word “shadows”. This word has seven letters. The seventh word following “shadows” is “all”...

Homework Statement A block having mass m and charge +Q is connected to an insulating spring having constant k. The block lies on a frictionless, insulating horizontal track, and the system is immersed in a uniform electric field of magnitude E as shown in the diagram. If the block is released...

I put an annoucement of this up in Announcements. There are some other links about it there, if you want more informaltion http://www.ccsem.infn.it/ef/emfcsc2008/pdf/Poster_ISSP2008.pdf What I want to do here is comment on the lineup of talks. The BALANCE in the theory topics is really...

Homework problem given by Count Iblis to the PF community: Consider a box containing a pendulum of total mass M in a spacecraft that is in free falling motion. Suppose that the engines of the spacecraft are turned on and the spacecraft is accelerating at acceleration a, where a is...

Homework Statement Homework Equations wave velocity = frequency * wave length The Attempt at a Solution Well...I'm not sure. I know how you could find the distance to the person to the right using trigonometric, but I don't know how to actually answer the question...

Come to know about any amazing plants(which do or have anything amazing) share it here!

An interesting Contest! I found this one interesting & easy; [PLAIN]www.ploysiam-gems.blogspot.com[/URL] comments welcomed.

I need to come up with a topic to present in one of my classes but I'm having a hard time coming up with something. I thought about doing a presentation on video security or how a cable box is securing the incoming video but someone else is doing it. I thought about maybe doing it on some type...

Say you had a universe, like our own in every way except that the total matter in existence was one single atom. Now say you introduced another atom of roughly the same dimensions into this universe as far from the original atom as spacially possible. How long, if any time at all, would it...

We look at a Laplace equation (\Delta u(x, y)=0) ) on a square [0, 1]* [0, 1] If we know that u|_{x = 0}= siny , u|_{x = 1}= cosy u'_{y}|_{y = 0}= 0 , u'_{y}|_{y = 1}= 0 we differentiate here by y. proove that |u|<=1.

:smile: http://funnyexamanswers.com/img/humandrawingis4.jpg http://www.funnyexamanswers.com/img/usecalctoproofofbatmanis.jpg interesting not exactly an exam answer but pretty interesting

The other day I was working in the lab and observed a very interesting fluid dynamic thing in a beaker: I was cooking acetone on a hot plate to clean a sample, then I see little bubbles on the surface bouncing around. The strange thing is that those bubbles act EXACTLY like a ball on a...

Hi, I'm trying to achieve neutral buoyancy with a sounding balloon (a large latex balloon). Is there a certain weight/helium ratio that will make it afloat at 10km/20km etc (tyhe balloon bursting altitude is ~38km) One idea that I had was to attach another balloon, which is mostly empty...

In the past three days I have strangled my brother to death (he was being a right pain) Saved the world from annihilation with my super powers, and traveled to Liverpool (I can't remember why now, I remember I was staying there for a week for some reason) had a relationship which broke up after...

That is impressive! Funny how little insignificant ants can get their act together better than a few third world countries...

these are really intestesting but i have no clue what the answers are... 1. You are having some friends over, so you venture to the store to purchase some soda and snacks. Unfortunately the only pop available is at room temp. In order to cool the cans of soda quickly you place the cans in the...

AP Chemistry -two interesting questions -- PLEASE HELP! Homework Statement 1. You are having some friends over, so you venture to the store to purchase some soda and snacks. Unfortunately the only pop available is at room temp. In order to cool the cans of soda quickly you place the cans in...

how can I show that ... arctan(1/v) = (π/2) - arctan(v) ?

how can I show that ... arctan(1/v) = (π/2) - arctan(v) ?

Hi there I need some advice, please: can you suggest any interesting cases of a driven, damped harmonic oscillator? I need to write a report (part of some assignment) on the mathematical model/behaviour/etc. of some real-world driven oscillator. No problems with the math, I'm just looking...

Q1: What is the box suggesting? http://img231.imageshack.us/img231/1514/whatistheboxsuggestinggy7.th.png a-126485704 b-673258719 c- 123456789 d- 627456934 e-176h54308 Q2. What is the fourth sequence in the following: 1.BRRRRRBB 2.RBRBRRBR 3. 4.? a- BRRRRRBB b- BRRBRBRR...

Can you make the following message unhidden? Niuzmzgd ffccul vgeen ffmal ffuzmzal jcd niuzmzgd vhmmni ognh Hint: O,I,U,Y,T,W,A,H,X,V,M

I've been re-reading https://www.amazon.com/dp/0465026567/?tag=pfamazon01-20 and came across an interesting algorithm. Start with any whole number. If it is even, halve it. If it is odd, triple it and add 1. Repeat until the number reaches 1. Count # of steps it took. Number/Count...

My lights stated to flash on and off at the same time i noted a series of bangs coming from outside, as i looked through the window i saw small explosions with puffs of smoke and debris traveling along the overhead power cable, it seems a tree branch had severed the cable, but why so many...

Very interesting... http://icanhascheezburger.com/2008/01/16/funny-pictures-i-sees-it-i-grabs-it/"

Homework Statement Let \Omega be a bounded domain in C whose boundary is a curve z = z(t), a<=t<=b, and let A(\Omega) be the area of \Omega. Prove that A(\Omega) = \frac{1}{2}\int^b_a |z(t)|^2 Im(\frac{z'(t)}{z(t)})dt Homework Equations The Attempt at a Solution Not even sure...