Explanation Definition and 955 Threads

1. A woman informs her engineer husband that "hot water will freeze faster than cold water". He calls this statement nonsense. She answers by saying that she had actually timed the freezing process for ice trays in the home refrigerator and found that the hot water does indeed freeze faster. As...

I've always wondered since I was a kid, I would lay down and have a blanket over my eyes sometimes while looking through it during daylight or at a light. If I focused just right, I would slowly see squiggly lines and things just slowly floating by like a transparent layer over what I normally...

Dirac's theory of the electron predicted that there were identical particles of equal mass but of negative energy. He appealed to the Pauli exclusion principle and proposed that there was a negative energy 'sea' of electrons that was full up to -2mc^2 in order to answer critics that positive...

Homework Statement Now in a revision lecture given a few weeks ago, the lecturer gave this as the answer. The Attempt at a Solution No I think generally I'm fine with it (apart from it doesn't seem very obvious that this is what you should do with the maths!). BUT 1)...

If one goes to a bookstore, one can find lots of books about String Theory. Unfortunately, many of these books are very difficult to comprehend; not everyone has the background necessary to appreciate these great works. To satisfy the curiosity of these people, I have decided to write this...

From treating light as a wave it is possible using Huygen’s theory to deduce that the frequency of the light will not change whether in vacuum or some other material. I have seen a mathematical proof of it and understand it but is there an intuitive explanation for it? Does it match Maxwell...

\frac{\partial_P}{\partial_y}(2ysinxcosx-y+2y^2e^{(xy^2)} I worked the first part no problem, but the second part I needed a little help from my calculator. This is what I got: 2sinxcosx-1+4ye^{(xy^2)} My question is, why does the partial of 2y^2e^{(xy^2)} come out to 4ye^{(xy^2)}...

Unless we figure out time travel (laughable), there is no way to come to a scientific explanation of the universe. All the 'theories' we have on the universe's beginnings are nothing but hypotheses...and that includes the big bang 'theory'...which is currently being shot to **** (Back and to the...

I need to explain fusion to some intro chem people, but they are really dense...Think this will work: *see picture

Ok, I know what happens (big fireball : ) when you add water to a chip pan fire, but I'd really appreciate it if you guys (and gals) helped me out with SCIENTIFICALLY describing WHY adding water to the pan causes the fireball. It must contain words like "immiscible" and so on... Thanks in...

Hi all, I am doing some homework from my textbook and I encountered this problem: "Starting from rest, a disk rotates about its central axis with constant angular acceleration. In 5.0 s, it rotates 25 rad. During that time, what are the magnitudes of (a) the angular acceleration and (b) the...

http://en.wikipedia.org/wiki/Depth_of_field" stands for the range that is sharp on a photograph. The bigger the diafragma (camera opening) the smaller the range that will be sharp on the picture. A bigger diafragma also means a shorter shutter opening (so the picture doesn't become too...

I know that when the applied frequency on a mass is equal to the natural frequency, the mass resonates. It has a great amplitude as a result of this. But I don't know how somethings affect the resonant frequency. Like for a mass-spring system. 1) What effect would increasing the mass have...

what is the scientifical (phycisistic) explanation of death? and what's the point in doing anything if we're just going to die? please, keep it short/simple, couse my head aches, and my english sucks..

Sorry bout putting the question in the form of like a homework problem, just didnt know how to go bout asking what i wanted. Basically can anyone explain how to do VLE calculations.. So confused with the topic. Whats bubblepoint and dew mean.. Cheers. Hopefully this post is ok for...

Can someone explain this to me simply. I just plain do not get Fourier Series. I've got a question that says: show that f(x)=exp(-cx) for 0<x<pi =exp(cx) for -pi<x<0 can be written as a cosine series that's way too complicated for me to work out how to write here. I have no idea...

How can one explain the Napierian logarithm without calculus?

Could anyone give me a brief explanation of how a capacitor works? What does its I-V graph look like? Thanks

Hi, could someone please give me a brief explanation of what entropy is? Due to my limited understanding what entropy actually is, most of the things I've read about it seem very vague. I've only been seeing entropy popping up in integrals and in sometimes in comments along the lines of entropy...

Hi, All my chemistry textbooks (thankfully not the physics ones) and my teachers (unfortunately including the physics ones) seem bent on 'explaining' the Heisenberg Position-Momentum Uncertainty Principle using the famous thought experiment of photons striking an electron, and not one of them...

If there is an explanation, I would appreciate undersanding them 1. The speed of light being (approx) 300,000 kms/sec rather than some other value? 2. That the speed of light is the same no matter what frame of reference (as per Einstein's theories and I assume it must have) 3. What is...

My lack of any shred of idea about the concept of the determinant is really beginning to bug me. Especially now that I have begun my Linear Algebra class. Is there anybody available to help explain (or link me to a good explanation) to me the idea behind it and what the value actually stands...

*** Elastic and Inelastic Collision explanation *** 1) Why energy and momentum are conserved in elastic collision? 2) Why only momentum is conserved in inelastic collision? Why energy is not conserved? Answers: Conservation of momentum is a consequence of Newton's third law. From the...

Hi I've got a question about a term in a formula I've found in Mandl&Shaw's QFT book It's about equation 2.18 on page 31 L(t) = {\sum_i \delta \bf{x}_i {\cal L}_i \ ... Why is there a delta x_i when summing over all lagrangians for getting the lagrange-function for the whole...

Hi all, for some time I have been wondering about something I’m not too sure on. Please could someone tell me how randomness can exist? That is to say on a molecular level, or on any level things happening without cause or justification? Patterns may be too hard for us to currently understand or...

Greetings, I've heard something to the effect that MOND can explain the rotation of galaxies, but the article was very fuzzy. Can someone please explain to me MOND... 1) How is MOND different from the inverse-square law? (math please) 2) What 'problems' in science does MOND...

Hi guys I am slightly confuse about a statement in the kinetic explanation for evaporation as well as melting. Firstly for the evaporation: "Thus the latent heat supplied in causing evaporation represents the potential energy gain of the escaping molecules plus the work needed to expand...

I was posting this on sciforums and it hasn't been debated yet so looking for opinions. But this forum is even better for physics discussions but I forgot the link to it since I used to visit here a couple years back. Anyhow, I will copy and paste my reply about gravitational forces: 'What...

In order to calculate flow rate when using a differential head pressure device, the simplified formula is Flow = (coefficient)(square root of the differential pressure) My question is why? Why the square root, can some explain this to me please? Thanks

The spread of a disease in a community is modeled by the following differential equation: dy/dx = 0.2y - 0.02x where y is the number of infected individuals in thousands, and x the time in days. 1) Show the equation that for the family of 'curves' in the x-y plane for which dy/dx is a...

Need explanation, please~~ Hi I am looking for the definition, and purpose of: COmputer AIded Manufacturing International

Could someone explain the wording (and possibly see if I'm going the right way about it) of this question to me. What is the current required in the windings of a long solenoid that has 1000 turns uniformly distributed over a length of 0.400m, o produce at the centre of the solenoid a...

There is a laser beam with a diameter D, in air that strikes a flat smooth piece of glass with angle @ and index of refraction of n. I need to derive and equation for the diameter of the beam in the glass wiht respect with n D, and @. I want to know why the beam's diameter would be effected by...

Hi Can someone please explain to me Eq 2.30 in Schroeder's and Peskin's book? (page 21) how does he simplify the long equation of the commutator to this delta distribution? \imath\delta^(^3^)\ (x - x') Thanks

Hey everyone, For math, I was given a quartic function. I was asked to find the coordinates of the points of inflection Q and R. Then to determine the points P and S, where the line QR intersects the quartic function again, and calculate the ratio PQ:QR:RS. So I found the points of...

Would someone, PLEEEEAAAASSSEEE, explain here how holography actually works. ...I mean - I know (I've already read about it times and times again) - I know it has to do with interference patterns (interaction between two components of light (object and reference light)), I see it has to do...

Consider this scenario: a Mars-size object strikes a glancing blow at Venus's backside that's facing toward the Sun. The resultant debris cloud would then coalesce into a large moon having a retrograde orbit. Tidal friction would then slow down Venus' rotation until it was tidally locked to its...

Every once in a while I try to stretch my feeble mind and pick up layman books on quantum physics as a change of pace from the many clinical/medical journals I have to constantly keep up with. I have a BS in chemistry and understand basic quantum mechanics but as much as I try, I cannot fully...

Since the nucleus of an atom is +charged and the electron is -charged, why doesn't at least one electron fall into the nucleus?

Hey, Just wondering: How does evolution explains the process by which some species, spceially from insects, have mimicry tactics for defense? Thx in advance, Mimicry: The phenomenon in which some species [the mimic] resembles another species [the model] and gains protection from the...

Hey, There is a question in my textbook that I don't understand the answer too. THey show a diagram of a baseball bat and say if the baseball bad it cut at the location of its center of mass, do the two pieces have the same mass? They say no, the piece with the handle will have less mass than...

hello Buoyancy is the upward force exerted on an object immersed in fluid, and upward force on an object in a fluid is equal to the weight of the fluid that was displaced. If this buoyant force is less than the weight of the object itself, the object will be left with a net downward force...

Someboy can give me an introductory explanation about dualities? I mean, what are, how works in theory and what physical sense do have it? I have to start some study about using dualities in linearized gravity, so i'll be very helped if you have too some basic literature at respect. Specifically...

Ok so far I have been thinking that an explosion is nothing else than a inelastic collision. So energy is lost and momentum is conserved therefore P_i = P_f , The problem asks for how much kinetic energy did each piece acquire in the explosion, I also know that there was 7800 J released. In...

okay i need help on rational functions I am not sure if that what they are called but it all should be the same.What i need to find is the holes zeros vertical asymtotes horizontal asymtotes and the slant asymtotes can someone please tell me how to find each on of those and the...

As part of a personal garage tinkering project, I am utilizing the equation (Faraday's?) to figure the voltage output of a DC induction coil (magnetic induction generator) with an air core and I have some questions about the equation: ∑ = -N{(∆B*A) / ∆t}. Where "A" is the area of the coil...

Would anyone like to suggest an "easy" explanation of how superconductivity occurs? Firstly, how the Cooper pairs form and secondly why that actually results in zero resistance? This is what I understand: An electron passes through the lattice and destorts it. This creates a region of...

Need explanation, please~~ A child slides down a slide with a 26° incline, and at the bottom her speed is precisely one-third what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child. I get as an answer 0.43...

hi all. Some clarification on this would be helpful to get me going in the correct direction. For a specified system, I'm trying to prove that the time it takes for the system to decay to 1/e of its original value (which works out to ~36.8%), takes a certain amount of time. The actual values...

I'm a peer leader for a general physics lab and someone asked me to explain what the Dot Product meant conceptually. I told him it was the projection of A onto B multiplied by the magnitude of B. He looked even more confused after that; my questions are: a) Did I explain it correctly...