Physics

Not sure where else to post it, seeing as the Physics GRE includes a variety of physics subjects, so here goes. I will soon start my senior year, and so I need to start thinking of the GREs. I am probably going to start studying for my Physics GRE soon, if not to take them before the stress of the senior year then at least to give myself enough time to practice. I downloaded the existing exams (there are about 4 online) and I will practice them, but I can't find a good source to get a bit more preparation as to what the exam is like, what to expect, maybe some methods of trying to deal with the time limits, etc. Does anyone has any good advice or resource to o…

How exactly do we know the structure of a nucleus? How certain are we that it is the right description?

What is the difference between Moment and Torque ?

This is a question I could not get a clear answer yet. When you theoretically turn time backwards, the attractive force of gravitation becomes repulsive. (I hope it is evident) What happen to the 2 other interactions? (the electroweak & the strong).

So I know that some theories allow for magnetic monopoles, and that including them would make Maxwell's Equations pretty and symmetrical. However, it seems to me that because we have true magnetic dipoles (ie they are not made of two magnetic monopoles) that having magnetic monopoles in addition would allow you to generate infinite energy as follows: Put a magnetic dipole somewhere, and guide a magnetic monopole in a closed loop along one of the dipole's magnetic field lines. Since at all times the monopole will be moving in the direction of the force it will gain energy. But where does this energy come from? The magnetic dipole as a fundamental property of things lik…

The definition of the Coloumb is the amount of electric charge transported in one second by a steady current of one ampere. Mathematically it's written as: [math]1 \mathrm{C} = 1 \mathrm{A} \cdot 1 \mathrm{s}[/math] or [math]1 \tfrac C s \cdot 1\mathrm{s}[/math] The defintion of Ampere is one coulomb of charge going past a given point per second: [math]\rm 1 A=1\tfrac Cs[/math] My question is: Why is the defintion of the Coloumb not written as [math]1 \mathrm{C} = \frac{1\mathrm{A}}{\mathrm{s}}[/math]

Two similiar barrels A and B with the same radius and mass roll down the same slope starting at the same instant.Barrel A is filled with liqued water, and barrel B is filled with ice of equal mass(Barrel B slightly longer than barrel A to compensate for the slightly larger density of liquid water) which barrel reaches the bottom of the slope first? and why?

what is the difference between solid and rigid (in physics) for example, a rigid object ..a solid object

I know its a dumb question but I wonder.. Which keeps you drier , walking or running in the rain? in other words, do you get wetter if you run or walk in the rain? .(the distance stable) and why?

Why does damp sand stick together?

http://en.wikipedia.org/wiki/Magnetic_charge - "monopole detection is an open problem in experimental physics" - "magnetic monopole particle has never been conclusively observed" - "has never been evidence for the existence of magnetic monopoles" How come magnetic monopoles supposedly do not exist, and why would it be hard to find evidence and conclusively observe magnetic monopole fields if all we need is a battery, wire, permanent magnet and know about Ampere's law? http://en.wikipedia.org/wiki/Ampere%27s_law So, obviously magnetic field of a moving charge has only one pole, right? Magnetic dipoles look like this: http://…

Why does lightning fork? In images of lightning, you see a multibranching, dendritic looking structure. Why doesn't it just follow the path of least resistance in a straight line? Is it really branching, or is that the afterimage of multiple strikes?

we go any further, it's important to get a clear idea of what time reversal symmetry really means. At the simplest level, we may think of the laws of physics as equations involving a time variable , and say that they are symmetric under time reversal if given any solution, and making the substitution , we obtain another solution. http://math.ucr.edu/home/baez/time/time.html What does t (and - t) stand for in physics ? only time ?

why not dot or comma why not circle et cetera.. why string?

Are there any theories out there that describe the properties of matter in theoretical higher dimensions? Specifically 3 dimensional time, two dimensional 'space.' (or time-space)

A truck driver carrying chickens to market is stopped at a weighing station.He bangs on the ide of the truck to frighten the chickens so that they will fly up and make the truck lighter.Will his scheme work?Does it make any difference if the truck is open or closed?

Invisibility, is it possible? If so how would you suggest doing it? Answers including active/optical camouflage as well as real invisibility welcome! Thanks

While browsing a client's youtube channel I came across video in his favorites section. I was immediately struck after watching it, and it seemed to just 'click' in my mind. I would like any of you to critique the theory or at least provide your opinion on it. The first thing that popped into my mind as far as questions go was: 'waves occuring in what medium?' If there is an aether-like substrate to the physical universe (well, what we perceive to be the physical universe), a wave action interference pattern would make the most sense to me. Whether that is composed of 'virtual particles' or a sea-like medium that only gives rise to 'real' particles' when waves int…

could a van de graaf generator dry your hair after a shower?

what is Novikov self-consistency principle?

Why does physics use the symbol p to represent momentum? It doesn't seem to fit because there is no p in momentum I know, m stands for mass. but Why p in momentum?

dot products, scalar products and inner products... are they same thing?

what does Yang-Mills field(and Yang-Mills particle ) mean? and also, what does Its Renormalization mean?

The gravitational and the electromagnetic forces are inverse-square forces.. but, why?

0.080 kg soccer ball is released from rest at a height of 1.24 m above the floor and after one bounce reaches a maximum height of 0.70 m. determine the amount of energy dissipated? commentary:my questions are not homework..because, I am not a student:)