Mystery Definition and 872 Threads

The question states: Ball bearing are made by letting spherical drops of molten metal fall inside a tall tower, and they solidify as they fall. a) If a bearing needs 4.0s to solidify, how high must the tower be? b) What is the bearing velocity when it reaches the bottom? c) What...

http://img.photobucket.com/albums/v235/gsan_bot/magnetic1.jpg" Refer to example 6.2 shown in the picture, the magnetic flux = -1.2t and the deriative time of magnetic flux should be -1.2, thus, the flux is decreasing and the direction of the induced current should be reverse. but why it say...

After doing some research on the subject I have managed to work out roughly how it works. What I havn't been able to find out is what it does. Were there any implications from this effect? Did it lead to disproving or proving a theory? Any help would be very usful.

The brain can sense the direction of a sound source by noting how much earlier a sound is heard in one ear than in the other. Model your ears as two sensors 19.0 cm apart. If a click from a distant source is heard 210 x 10^-6 s earlier in the left ear than in the right, from what direction...

I've been kicking myself in the head all day trying to figure this one out. I'm completely bewildered.:rolleyes: Please help meeee! A stone is thrown vertically upward at a speed of 43.00 m/s at time t=0. A second stone is thrown upward with the same speed 2.250 seconds later. At what...

not able to pick up a 1 kg iron object off the ground by overcoming the gravitational force between Earth and the object. Consider this : It can pick up a 1 gram (iron) object easily. Then, the increase (from 1gm to 1 kg) would be by a 1000 times. Clearly that increase cannot account for the...

Help me out please, a friend sent this to me and I can't seem to figure it out. Thanks! "Congresswoman Smith opened the Post and saw that a bean-counting scandal had been leaked to the press. Outraged, Smith immediately called an emergency meeting with the five other members of the Special...

I still don't quite fully understand about the order of poles and calculating residues. Take f(z) = 1/sin z at z=0 for example. When I try putting that into Laurent expansion about z=0, 1/ sin z = 2i/ (e^z - e^(-z)) = 2ie^(-z) / ( 1 - e^(-2z)) = 2ie^(-z) [ 1 - e^(-2z) + e^(-4z) - e^(-6z) +...

Hello all. I have a dell inspiron 1525 laptop, and I've had it for about 4 months. I've been downloading music here and there, but nothing too major. Earlier this week I realized that my computer had used about 70gb of memory, and I had no idea where it was. So I downloaded a disk analyzer...

I'm curious as to why there aren't heavier metals in the Earth's core than iron and nickel. Why those two? Anyone have any insight?

Is it a turtle or a monster?? :) http://www.newsday.com/news/columnists/ny-lijoy0801,0,5138315.column

Who are you people that can type fast, where the heck did you learn this skill, it seems that there are people out there that can type with more than one finger, what the hey are you people mutants?

I've learned that photons have no mass, so why they are still influenced by black holes or other large celestial bodies?

Can someone give me a list of problems which at first sight require the axiom of choice, but do not?

free energy?? water disasotiates to H+ and 0H- if you could take the dissasociated ions away, and combine them how much energy could you get out? In the liquid remaining, more would dissosciate, and the process could be continued. Where does this energy come from - it sounds like free...

I'm searching for a datasheet. This IC device is a two-wire, differental, digital transmitter. Each leg has three output states (hi, lo, gnd). The otputs are differential and trapizoidal in shape. The logo on the chip is a solid white triangle with the point upward. And a Google search...

The 3 pions have different masses and we say this so because of the electro magnetic energy.if this is so then we can never measure a mass because the magnitude of the EM energy that a particle receives depends on the charged particles around it. if you help with this dilemma i would be grateful.

A very interesting article for all. http://www.math.utah.edu/~palais/pi.html Quote from the article: "What really worries me is that the first thing we broadcast to the cosmos to demonstrate our 'intelligence' is 3.14... I am a bit concerned about what the lifeforms who receive it will do...

Recently, a rather large nothing was discovered in the Universe (last August by the University of Minnesota team). This cosmic blank spot has no stray stars, no black holes, not even dark matter, and is a billion light years across. Is there a possibility that this could be the result of a...

Hi all. I can't remember where I saw this but it really confuses me. If x = .999999999... 10x = 9.9999999... 10x - x = 9x x = 1? So does that mean if that .9 recurring is 1 exactly? Thanks for any help.

Hi everyone, Can anybody solve my simple problems of quantum: Usually we say, that wave function Ψ is dependent on r,θ,Φ .But this is just a coordinate system,or more than that. Imagination to this is qite difficult. Moreover somewhere in a book I have read that if Ψ = f(r,θ) exp(imΦ),then on...

Homework Statement We did an experiment in class abvout resistance and temperature. The teacher told us to find out why light bulbs usually blow when you turn on the light. It must be related to the experiment we did which was seeing how resistance changed with temperature Homework...

i got a atronphysics question that i have a hard time to solve it: In the most massive stars, nuclear fusion continues until iron-56 is formed in the core. consider the net process, which is to take 56 hydrogen atoms and turn them into one iron atom. a, how much enegry is released per atom...

Hi, i recently constructed a hofmann apparatus at home out of pvc and had some trouble with it. Basically, once it is set up, i only get gas from one electrode, the other does nothing. H2SO4 is used as the electrolyte, and the is 12 volts at 4 amps being put through it, DC. are there any simple...

ok my doubt is wen i look at a concave mirror(behind focus of mirror) i can see image of my face inverted inside the mirror,,,why does this hapen?? acc to mirror laws i shud get a real image tht too not inside the mirror but outside it! y do i observe an inverted virtual image in case of...

Red light mixed with green light produces yellow light. Yet, a red photon and a green photon don't combine to make a yellow photon (or two of them). Can someone explain this?

Hi there, this is my first ever post in PF. Have you heard of crystal babies? They have been very popular among Taiwan students. And I have googled some information and some people said they consisted of "arcrylate polymers". They also said they are similar to Magic/Crystal Soil. Would...

0.999... = 1 ?? Hey, I was just reading about this and thought it was interesting. Apparently, from what I have read, 0.999... = 1 (where the 999... represent an infinite series of 9's) There were a few good arguments for this 'fact' and also a few arguments against it... What I...

The origin of the Huns is a mystery and subject of much debate. They originated in the Steppes of Central Asia as did other groups. There is evidence that they are a Turkic or proto-Turkic group. The Chinese (Qin) referred to Hsiung-nu (Xiongnu), and some/many consider this an early reference...

Can anyone explain how flying ring works? like the demostration whith a magnetic coil connected to AC poer and an aluminum ring. the ring was placed on the top of the coil and althought aluminum is a non magnetic, the ring was thrown to the ceiling. can anyone tell me why there was force on...

The other day, when I was traveling in the car, on a really, really, scorching, sunny day, in the distance I noticed that the road looked watery.Anyone knows why that happened? PS:There is no problems in my eyes.Even my Mom,Dad and brother noticed it.

Homework Statement The sum of 8 positive integers is 31. If no individual integer value can appear more than twice in the list of 8 integers, what is the greatest possible value that one of the integers can have? Homework Equations ? The Attempt at a Solution My answer is 16. I did a lot of...

can someone explain to me how did it derived to the ARROW... I am not quite sure how that happened.thanks

Has anyone come across this operator ? \frac{\partial^2}{\partial_x\partial_y} + \frac{\partial^2}{\partial_x\partial_z} + \frac{\partial^2}{\partial_z\partial_y} I've never seen it until it came up in a field theory context. What can it mean ?

Hello everyone! I've encountered a small problem with one of our "special" assignments. Question: The normal boiling point for ethyl alcohol is 78.4 C, S for C2H5OH(g) is 282,7 J/mol*K. At what temperature is the vapor pressure of ethyl alcohol 357 mm Hg? Maybe I'm stupid, but I can't find...

Hi , everyone I have a problem with geodesic equation . I know the method of solving it , but I can't understand the solutions . When I tried to solve it for a torus I arrived at : \dot{u} = \frac{k} {{\left( {c + a\cos v} \right)^2 }} \] \[ \dot v = \pm \sqrt { - \frac{{k^2 }}...

Sequences HELP! Homework Statement Show that the sequence Cn = [(-1)^n * 1/n!] Homework Equations The Attempt at a Solution This is an example in my book but I am not understanding it... It says to find 2 convergent sequences that can be related to the given sequence. 2 possibilities are...

I was having a glass of wine over candlelight and I noticed that the liquid wax was completely transparent but turned opaque when when the wax solidified. Why does this happen? Clearly, when the molecules reorganize during the freezing phase transition they begin to interact with the light...

1. Light at the blue end of the spectrum penetrates most easily underwater. Why are seaweeds often yellow-brown in colour? Does anyone know why this phenomena occurs? Thanks

about coloumb? i wonder why two point charge whose magnitude 0 and +q(or smt different from zero charge) exert a coloumb force to one another .formula says there shoud be no force acting to each other(because of multiplication q1.q2=0) but there is an atraction between them . if this force...

I went to use one of my roasting tins and found a layer of glue like substance in it, the last time i used it was for roasting potatoes and i used vegetable oil, now i may have forgotten to wash it but surely veg oil does not set like glue, i had a devil of a time cleaning this stuff out it...

[SIZE="4"][FONT="Palatino Linotype"]Hi, This is my question: why is in the middle of ice, white ? (have you noticed ?) I guess the reason must be that water molecules don't have enough space to expand naturally and form symmerical crystals; and the white colour is because of this...

http://www.npr.org/templates/story/story.php?storyId=88520025 Interesting, especially when you consider that this winter has been the coldest in over 100 years in many places around the globe.

I'm trying to deal a problem using this formula, but I'm unclear as to what dl represents (Or if it is the same as dx in most integrals, then in that case I don't know what the lowercase L is) {\cal{E}} = \int_{a}^{b} \vec{E} \cdot \vec{dl}

When you boil an egg it turns into a solid. Isn't that kind of weird?? I thought when you heated a liquid/semi-liquid it will turn into a gas. But on the other hand I get one of my fav. breakfast. HOW?

So, you have steak which you toss on a hot pan. The heat eventually break apart the molecules, making oxygen and hydrogen evaporate and you are left with just carbon, a burnt crust on your steak. My question is, why does this change when you use oil or fat? I have two possible solutions...

What relationship do 5 and 6 have that make them unlike any other pair of distinct positive integers under 1000? (1000 was as far as I tested.) WARNING: Don't read the rest of this thread if you want to solve the puzzle for yourself. It's not that hard--my dad got something rather close to...

Hi, I am facing difficulty in trying to prove how the mathematical relation for WORK W = force X distance it might sound strange to a few but I was wondering how it was decided upon that force has to be multiplied by distance and not added or something else! Its understandable that to...

When I bought that useless budgie for W's birthday (she really wanted one), I just automatically started putting a towel over her cage at bed-time (the bird, not W). That's because everyone that I've ever known who had a bird did that. Why do we do that? I know that the thing has a brain the...

Hi all, I am having a hard time understanding the following scenario (I'm quoting from page 305 of the "Electricity & Magnetism" textbook which you can access via Google Books): "Assume a simple model for an atom which consists of a point nucleus (+q) surrounded by a uniformly charged...