Mystery — 395 discussions

Hi, in one (hep-th) paper I found the term "target space" and I can not find any reasonable explanation of this. Do you know anyone this term? Thanks, Michal

I recently started studying biology because suddenly I started getting curious about this subject. I read about the cell theory which states that all living things have cells. Is this necessary - that all living things have cells? Can't they have some different structure? Also these type of...

Hi everyone! How do these two types of energy work for things that are being lowered down slowly? I've been told that whenever one drops something (let's say it's 1kg) from 5 meters, it will be traveling at 10 meters per second just before it stops at the ground. And I've also learned that...

Hi all, I would like to take an official version of the ACS exam for Organic Chemistry, but I cannot find out how to do this. I took an old version as part of my 2nd Semester Community College OChem Final, but those scores don't count officially. I really want to take a current version soon...

Hi, A fundamental aspect in the Hamiltonian framework of mechanics is that the q's and p's are independent. I feel like I understand the steps in the Legendre transform from Lagrangian to Hamiltonian mechanics, but I don't see how you can go from a system where only the q's are independent...

Homework Statement Star A and B are at rest relative to Earth. Star A is 27 ly from Earth, and as viewed from Earth, Star B is located beyond (behind) star A. (a) Star A is 27 ly from Earth. A spaceship makes a trip from Earth to star A at a speed such that the trip from Earth to Star A takes...

hello EveryBody, In the 3D Coordinates I always find 4 parameters instead of 3. A = (X, Y, Z, 1) I wonder why? thank you.

I am confused as to how heat transfer really works. I've read all about conduction/convection/radiation. Radiation makes sense to me, electrons enter a higher band, come back down and give off energy in the form of EM waves. These waves can then be absorbed by other atoms causing electrons to...

Today i watched Discovery about the fate of the universe. One of the presenters said that finally all the energies used up and the universe will be in deep freeze. My question is where all the energies go? What about conservation of energies? Thank you.

Biggest problem which LHC is worried about is knowing how mass is related to particles.does this mean that physical significance or understanding about charge is discovered.? If yes,what charge is.? If No,why scientists are not concerned to know about what fundamental charge is by conducting...

A wedge with face inclined at an angle theta to the horizontal is fixed on a rotating turntable. A block of mass m rests on the inclined plane and the coefficient of static friction between the block and the wedge is μ. The block is to remain at position R from the center of the turntable, as...

The theorem supposedly states: A space cannot be bent unless it is a manifold which is embedded in a space of at least one higher dimension. Does anyone know if this theorem actually exists? If it does, I would appreciate a reference to its name and proof.

OK fizziks guys, here's a puzzle. Took this pic at a friend's house today. They have a wood-burning stove in the room. The ceiling and wall are blackened with soot where ever there is a stud. I can't think of any explanation. Some deets: - the room is a closed-in porch, probably uninsulated or...

I know that cosmic string have intense energy and are apparently leftovers from the big bang and can create a sort of gravitational time distortion field, But HOW did these form from the Big Bang? Can their existence be backed up by other models?

Homework Statement Why does the compass turn right when a magnetic field other than the Earth is applied? This has been bugging me for a while, does anyone know the answer to this question? Thanks a lot :p Homework Equations None The Attempt at a Solution None

Hi I am reading about lock-in amplifiers, and I read that the low-pass filter in a lock-in amplifier acts as an "integrator", since much of the noise that ends up in the DC output of the multiplier will integrate to zero. How is it that the low-pass filter can do that? I would appreicate...

Hi can anyone help : Are there different categories of ISM dust ? Where is the dust thought to have come from? Many thanks

I mean, If an ideal step up transformer increases the voltage from 10V to 20V say, why does the current halve? I know it happens and I know the equations for it, I know to say otherwise would contradict the law that energy cannot be created. But putting the equations aside, why exactly...

I am confused that many web sites say that it took 25 N to crack the egg, it's ok but When I do the drop test with 8 meter building. So, I calculate the force: 1kg(box) * 9.81m/s^2 So, the force tat impact my box is 9.81 Newton but the egg was crack. I just confuse!

Hey all, I am looking at the American Wire Gauge chart listed on Wiki (http://en.wikipedia.org/wiki/American_wire_gauge"]).[/PLAIN] I am attempting to determine how they are getting their copper resistance values. From my education, DC resistance is equal to...

Something is totally not making sense. In a complex scalar field theory, I have two field degrees of freedom, which I parametrize in polar field coordinates: \phi = \rho e^{i\theta}/\sqrt{2}, where \rho and \theta are real-valued; and its Lagrangian takes the form: \mathcal{L} =...

Catching up on the Universe Today I came across this article discussing the history of the wow signal. Since it fit the profile of a non-naturally generated signal, the would indicate either an equipment glitch or there really was something out there sending a signal. My question is, based on...

I've encountered a problem that I can't seem to make any logical sense of. Hopefully someone here can help! I have a 24VDC motor with an attached electric brake to prevent back-driving. The motor is controlled with a 5V analog joystick. The joystick has a button that needs to be pressed to...

Hi, I'm new here, and not *really* a physics student, just a guy trying to wrap his head around science by reading lots of books! Stuck on a well known theory, which in my head does not make sense, and hoping someone can clarify... Homework Statement A quantum Eraser - this works by...

Feynman said that " [the double slit int. pattern contains] the only mystery in QM" was quantum entanglement not established (and bells theorem not postulated) then yet? or did Feynman believe that the explanation for the double slit (interference pattern) would also somehow explain...

I've built a Darlington pair from 2N2222 NPN transistors on my breadboard, and I find that just my touching of the base lead in the circuit cascades both transistors and let's current flow in the circuit. What's causing this? See the video below for details.

I noticed that the temperature coefficient of resistivity of pure silicon is a rather high negative number, so just out of curiosity I wanted to see at what temp the resistivity would drop to zero. The formula is ρ-ρ0 = ρ0α(T-T0) where ρ is the final resistivity, ρ0 is the reference...

Hi guys, I know I may sound stupid to me many of you but can anybody tell me what does 'rfac' do in Fortran.

In the green box in the paint doc it says " The motion diagram shows that the particle's acceleration points to the right... Umm what are they referring to because it looks to me like the green arrows are pointing to the left...

Hello. This is probably a silly question. But it is something I haven't been able to find an answer too. When I connect something to my laptop through the USB, I know that there is 5V coming from the USB connection ...there are many pinout diagrams about that show this. But what is the...

Hi! Special relativity states that nothing can travel faster than c. But how do we know that c is the speed of light?

I was watching a programme on anti matter 'discovery' whereby a guy claimed that research is going on to create this... The way this guy described the energy was that if a 'anti matter' clone of himself was to touch him, both him and the surroundings would be obliterated.. He claimed that...

Homework Statement Vectors A and B have scalar product -6.00 and their vector product has magnitude 4.00. What is the angle between these two vectors?Homework Equations A \dot B = ||A|| ||B|| cos θ and A \cross B = ||A|| ||B|| sin θThe Attempt at a Solution Then I reasoned that tan(θ) = -4/6 so...

A car is at rest , the driver let's off the brake and hits car in front, the cars were 5 feet apart prior. No damage is apparent, later, front car claims back chrome bumper has dent. Is there a formula to prove or disprove the required force to dent the chrome bumper? What other info would be...

The more time away from the gravitational field near the faster, so those who fall into the black hole horizon material time will be very fast, from the outside in acceleration seems to matter, the decay material gradually disappear, and the material in the horizon to listen to the light should...

This has been bugging me and I just can't seem to figure out a solid answer. My electric stove has different sized heating elements where the size comes from just a longer heating element. It looks like this: http://www.sausagemaker.com/ProductImages/41516.jpg When I measure the...

Homework Statement I encountered this past exam paper question in Hong Kong when I was giving tutorial to a high school student. I am confused with the answer provided by the official authority. The question is (in exact wordings): Homework Equations The Attempt at a Solution The friction f...

Homework Statement Machine A can do a job, working alone, in 4 hours less than machine B. Working together, they can complete the job in 5 hours. How long would it take each machine, working alone, to complete the job? Homework Equations Ans. Machine A: 8.4 hours; machine B: 12.4...

a hole is the absence of electron..so basically its just a vacancy.. so why does it have a mass??..how can a vacancy have a mass and dat too greater than electron itself??..can any1 pleasez help..

if a mass is hangig from ceiling of a car the car starts to accelerate forward with acceleration greater than g the mass will rotate and then starts to accelerate forward wheil its in the same position making an angle with the vertical my question what caused the rotation? i know there is...

Im having trouble understating this: The last part: DEz=8333N(5/15) where does this come from? 15m is the height and 5m is the base of the triangle.

I heard from a friend that such a thing was recently discovered. Any news on this?

In (the partial) solution, why does it consider the Tension,T, for finding the friction force between m1 and the surface? The tension is only affecting m1 in the horizontal direction. From where, the vertical component is apperaing?

Homework Statement A passenger is standing without slipping in a forward accelerating train. The coefficient of static friction between the feet and floor is 0.47 a) Draw an FBD for the passenger in Earth's frame of reference b)Draw an FBD for the passenger in the train's frame of reference...

Interesting article. http://news.yahoo.com/cyclops-shark-other-cryptic-creatures-october-creepy-113008213.html

Hi l have this question in my mind l never found a good reference for the answer . my question is to know how did they find the number of electrons for an element ? l am not talking about how to read the table to know , but how that table was made ? what process was used to figure out...

My mate and I are neutralizing (what we think is) a 2.5 gallon carboy of 10% HNO3 and 1% HF solution. Reason: We want to pour this stuff down the drain and be done with it. We use calcium hydroxide because we didn't want to create any sodium fluoride (nasty stuff that it is) from using soda...

I don't recall ever trying a mystery sound competition. So, in the fashion of other competitions, whoever can name the source of the sound picks out the next mystery. The imagery in this video is irrelevant and not intended as a clue or a false lead...

I'm new to this site, so let me know if I'm doing anything wrong. Homework Statement I have attached the original problem in a PDF file. I have to read a murder mystery story and pull information from it to plug into kinematic equations and find out who commited the murder. Important...

A few months ago I was surfing idly and found this little thing called a Gravity Train. For those who do not know what it is, see http://en.wikipedia.org/wiki/Gravity_railroad" . After reading about it I thought maybe I should try and find out how much time it would take (42.2 minutes) but...