Mystery Definition and 913 Threads

I found a folder of ancient motorbike mags on my porch, can you imagine my joy? No one loves or even likes me enough to give me such a gift, they are probably priceless, well worth a few bob anyway, who the heck?

k the question states On a pleasant fall day (temperature of 21.0 degree Celcius) a lump of clay (with mass of .855 kg) is thrown against the wall with a speed of 38.0 m/s. The clay deforms as it sticks to the wall, noiselessly. Assuming no heat escapes into the air, what will be the...

Riddle 1 30 Prisoners are on death-row for marijuana related offences. The prison warder doesn't view their crimes with much seriousness,and decides to give them a chance to escape.He makes the prisoners the following offer: Tomorrow all the prisoners will be blindfolded, and either a black...

I wondered why it is that when you multiply a negative with a negative, you get a positive? in example; why is it that -3 x -3 = 9? when you do -3 x 3, the answer is intuitively -9, because you just go three times as negative. But when I multiply two minus signs, I don't have this...

For the past year I haven't been able to keep milk in my fridge for more than 4-5 days. I always buy the freshest milk, not expiring for a couple weeks from purchase. However, the milk sours in my fridge in 4-5 days no matter what brand or size of milk. After 4-5 days the top of the milk is...

Carbon dating! A 5g charcoal sample from an ancient fire pit has a 14C activity of 63 disintegrations per minute. A living tree has a 14C activity of 15 disintegrations per minute per 1g. The half-life of 14C is 5730 years. How old is the charcoal sample from the ancient fire pit...

One of the factors that can produce a winning F1 car is the understanding of turbulent flow, the people that design these cars spend millions on wind tunnels, simply because turbulent flow has not yielded to mathematics, my way of thinking is ,that it is essential to understand turbulent flow...

This is a very curious situation. I have a large water tank on the top of a hill. It supplies a gravity fed water system that works fine. There is an under ground pipe with one end A in the bottom of the tank. The other end E is about 80 feet below A, and has a faucet. None of the pipe is...

what does a big inverted V stand for? it's not "and" because it's used right in front of a literal (atomic formula) not sure if it's a quantifier... This is a paper discussing approach based on deontic logic that I am scanning through, but this sign i cannot figure out how to search online...

I'm just wondering whether anyone has any theories as to what causes the electrons in the Aurora Borealis to accelerate (emitting e.m radiation)?

It is often stated that ANY accelerating charge radiates, so this includes uniformly accelerating charges. But the radiation reaction force is proportional to the THIRD derivative of x, so it vanishes when acceleration is constant. What's the deal here? Here's a graph which supposedly shows...

I'm often slow on the uptake, but this is ridiculous. I just figured out what the pointy hair represents in Dilbert's pointy haired boss.

How does cold air travel? Isn't it like me flashing darkness at your face? Because cold is the absence of heat as darkness is absence of light. It's like nothing traveling. I know it's confusing.:confused:

Hi everyone, I have just read an article about the discovery of a ring of a dark matter. In fact I do not understand this matter very much, except that it has great gravitational field in space. Can anyone explain shortly about that or just give me some web links that I can read about that...

I'm currently going through some questions and came across quadratic and linear simultaneous equations. Solve the equation: x + y = 1 x^2 + y^2 = 16 I am not interested in the question itself but rather the explanation the book gives me which says after...

I just read that the mystery of the "missing solar Neutrinos" has been solved. That is, the "missing" stuff is converted to Muon & Tau Neutrinos (which have been detected at the SNO). I'm confused ... If Solar Neutrinos are very "non-interactive", then how do enough of them get converted...

I was wondering, if dark matter (DM) halos are spherical in nature and increase in density as a function of distance from the galactic core, why does the density drop off so suddenly and why would stars on the edge of a galaxy feel an inward pull? To elaborate on the 2nd question, if DM...

I thought optical phonons only existed in crystals with two or more types of atoms in a unit cell. But I keep reading references of optical phonons in single atom crystals, like silicon. What's the deal here?

So black holes are incredibly dense points of matter that affect everything in their area with very powerful gravity field, including light. \ So, asuming that gravity affects only matter, that by default says that light is a physical particle. So why don't the regular laws apply to it...

Hi, I've been learning about transistors lately through the Horowitz & Hill book. I'm surprised to see that when used as a current source the collector voltage only changes with load voltage with an ideal transistor. When I say I'm surprised I mean that in non-ideal models the base current...

This is a coursework question, but i know the answer i don't understand why it's correct. "A proton antiproton collider produces a pair of top quarks, draw a Feymann diagram of this process that involves a single gluon." the answer being that 2 like quark/antiquark ( u & u bar or d & d...

Simultaneity Let's imagine there is a train moving at the speed of light. When in the middle, two lightning flashes appear on it's left and right. Why is it that it sees the right flash before the left? And if it is moving left to right, why does it see the left before the right? It is to...

I found a powder in my driveway earlier today. I have no idea where it could have come from but I'm curious because it seems so out of place. It's very dark brown, almost, but not quite black (see attached) and utterly uniform in colour. It's extremely fine, finer than icing sugar. So fine...

Hey Chem geniuses! I am a struggling high school chem student who couldn't combine water with water without blowing something up so some help would definitley be appreciated. My chem final has been issued already and it is as follows: Put 5 mL of 3 M aluminum chloride solution in each...

http://www.collegehumor.com/video:1755006 This may be old but... How does this work? They need to have a huge warmth transfer coefficient for this to happen? Maybe the water is at 0°C already and a small amount of energy should be taken to get this effect. Is it electromagnetical or is the...

I just read the following fact and it somewhat defies my usual logic. \lim_{x\to\infty} \sqrt{x^2+x} - x =\frac{1}{2}. Now my usual logic tells me that as x becomes large, the leading term in a polynomial sequence is the major one and therefore the x^2+x becomes x^2 so \sqrt{x^2+x} becomes...

So I learned today that Bleen is the integer number between 6 and 7. You might be a little upset about this. However, bleen can still be useful to you, since it is also related to Grue, a very convenient term not to distinguishing blue from green in language. The philosophical implications of...

Say we have two waves of the same amplitude are about to collide with each other. The preceeding wave travels at a slightly higher speed before interacting with the final wave. However, instead of passing through the final wave its speed and size is transferred into the final wave where it...

I was staring at my calculus book when this came to me, so apologies if its a little murky. I've been thinking about Hubble time and noticing something odd, that my astronomy professor really couldn't (or wouldn't) answer. t(u)= 1/H x 10e12 years which didn't quite work because if the...

There are two magnets stuck together through magnetic force but there is a pane of glass seperating them, when I spin the magnet closest to me clockwise, both of the magnets spin and move to the right and down, when I spin them anti-clockwise, they spin and move to the left and down. The...

What causes the horizontal lines that move down a computer or TV screen when you video tape it?

We know that Truthers always tell the truth but Liars will always speak falsely. An island comprises entirely of Liars and Truthers.. Precisely 45 people attended a dinner in the island. Each one of them sat at a big round table. After the dinner was over, each of the attendees was...

How does a photon move.If it is a particle and moves in a straight line,what do we mean by its frequency in E=hf?

An evil king has n bottles of wine, and a spy has just poisoned one of them. Unfortunately, they do not know which one it is. The poison is very deadly; just one drop diluted even a billion to one will still kill. Even so, it takes a full month for the poison to take effect. Design a scheme...

1. do different people have different dreams? 2. how often does one dream? 3.what affects the dreams that one has? 4. why do we often forget the dreams we had?

[sorry if this has been asked before, but this is a question I've been asking people] Ok, now just about every one at one point has heard about a "ghost". And lately I have been thinking to myself that I have been seeing them around the house, because when i come out of a room, and i pass...

The color code for hidden text is #black. Some of these questions are insanely tough. I'll post the answers after sufficient participation. 1) The first is a picture of a person who starred in a famous American sitcom of the seventies. The second is of a famous director. The third is that of...

Wow, this forum seems to be full of engineering brilliance :P. Anyway can anyone help me with this. The stages in sand casting to produce: a) solid object that is thinner at the centre than at the ends b) hollow object with two openings of diameters less than the component diameter...

In fusor you react one deuterium with another one. So you should get 4He2. Why does it ejects one proton or neutron from nucleus?

Two people sat eating fish and chips in the open air...both see a car shift sideways. There was no way for it to have done so and it did not make a sound as it moved. One minute it was there...the next it shifted a foot or so sideways. Both people stopped mid chip and looked at each other for...

It seems reasonable to start a thread about this. Please feel free to post any pertinent information. For starters, see the main page of NUFORC - The National UFO Reporting Center. http://www.nuforc.org/ This is the report database for Illinois. See November 7th, 2006...

I saw a bright green meteor yesterday. What would cause a meteor to be bright green? Is this common?

At work we have these magnetic blocks which have arms attached to them for dial indicators. They are use to hold the dial indicators like an extra pair of hands. They work great. My question is how do they work!? The magnetic block has a switch on it. This switch will turn the magnet on...

Homework Statement Why F=ma? And what is mass? Homework Equations The Attempt at a Solution

I just thought of something, imagine this scenario: You have an empty bottle of sode\water(whatever) and you hold it lopsided, at the point where it theoretically would stand still. But then move the top half a millimeter towards the center, and then release it. Then it will "fall" to the...

I found this to be an interesting article by Benjamin Radford on orb photography. Anyone have any photos with really unexplained effects? I tend to think that most "orb" photographs I've seen are so obviously dust or small insects. Who was the first to claim dust was actually "ghosts" Does...

Here I have an elusive schematic of a 20 dB amp at around 20 MHz. It works as a unity gain amp when the control line IFG2 is open. When grounded it amplifies by 20 dB. The diode is a pin diode and supposedly has 83 ohms when the current is flowing through it. The +10 volts comes from a...

I have found a quote I've been looking for. It's the lower one in my signature right now: "Science is everything we understand well enough to explain to a computer. Art is everything else." However I don't know just who said it. Most web sources say David Knuth, but some say Donald Knuth...

Today the professor wrote down the following for use in an integral: \frac{1}{2}cos(2\theta)=sin\theta cos\theta i am not sure is this is correct. i have tried to prove this and cannot, i have also not found it in an table of trig identities. Is this a valid identity? i am not sure since...

an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron? I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it can't be determined with this info why not?