Particles Definition and 1000 Threads

Homework Statement Three perfectly elastic particles A, B, C with masses 4 kg, 2 kg, 3 kg respectively, lie at rest in a straight line on a smooth horizontal table. Particle A is projected towards B with speed 15 m/s and after A has collided with B, B collides with C. Find the velocities of the...

Homework Statement Please refer to both figures. The result of the example problem was θ=33.2° Homework Equations ΣFn=man The Attempt at a Solution I am stumped. I thought you could solve the forces in the z direction, straight up from the car, and set that to zero since there is no...

Double-slit experiments have been done to death, Obtaining and preserving which-path information (or otherwise) for a particle or photon causes its entangled partner to show the probability distribution with or without the interference pattern, violating Bell's inequality and thus proving...

Homework Statement Refer to figure please. Homework Equations ∑Fy=0 before string is cut The Attempt at a Solution I tried summing the two forces in the y direction before the strings were cut which would be the two tensions at a sin40° and minus the weight of the ball(mg). That gave me T in...

Hi all, I've read a number of posts on virtual particles (including one of my own), but I'm still confused about one aspect - the interaction between real and virtual particles. Say we have an electron moving from position A to position B. As the electron moves, there should be virtual...

I've heard of photons being described as a wave/particle duality. But what evidence is there that individual photons behave like anything other than a particle? I can see how photons en masse can display wave/particle characteristics, but what evidence is there that any individual photon...

Hi, I am working my way thought Hartle's Gravity. In Section 5.4 he states that "The straight lines along which free particles move in spacetime are paths of longest proper time" and proceeds to proof that "in flat space time the proper time is a curve of extremal proper time". Can someone...

What happens when charged particles fall into a black hole? Say like N electrons fall in, giving the black hole a net charge of -N. Since light cannot escape the event horizon, I imagine electric fields cannot either, since they are mediated by photons. So is that charge effectively lost until...

Layman question. In the Standard Model every fundamental force has associated particles, force carriers. We know that at sufficiently high energy levels electromagnetism and the weak nuclear force become unified in the electroweak force, and it seems likely that at even higher energies also the...

Hi. In some statistical approaches (e.g. canonical ensemble), the particles of an ideal gas are non-interacting. Still, it's possible to derive the ideal gas law and other thermodynamic relations. Wikipedia gives an equation for the speed of sound in an ideal gas. How can there be waves in a...

Hi, I read quite a few popular science books and try to wrap my head around quantum physics. I am reading Stephen Hawking's "Theory of everything" again in which he explains the double slit experiment and how particles take every possible path in the universe (with some paths being more likely...

In classical field theory, the field, φ, is usually constructed from a very large number of coupled harmonic oscillators. Let's say our φ consists of just electrons. What does φ best represent physically, a very large number of electrons or can it represent just a few electrons? Which is the...

Homework Statement Onto an Aluminium 50μm thick plate, we send a beam of alpha particles with unknown kinetic energy. the cross section of the beam is 2cm2, density 1013 / scm2 . Whats the kinetic energy of the particles if every second we sense 105 scattered particles between the angles 40°...

Is it possible to have identical quantum particles that are distinguishable? By identical, I only mean that all particle properties like mass, spin, charge, etc., are identical. My guess would be no because the only thing that could tell the two apart is their trajectories, but their...

Hi, I am studying the Higgs discovery and I've got a doubt. One of the process used to discover Higgs is the decay H -> γγ in 2 photons. At LHC there are detectors of photons that can measure energy and momentum of them. So if you measure the energy and the momentum of both, you can calculate...

Homework Statement For a system of discrete point particles the energy momentum takes the form T_{\mu \nu} = \sum_a \frac{p_\mu^{(a)}p_\nu^{(a)}}{p^{0(a)}} \delta^{(3)}(\vec{x}-\vec{x}^{(a)}), where the index a labels the different particles. Show that, for a dense collection of particles...

I been studying quantum field theory and standard model lately. I not see how a unified theory could fit between quantum field and special or general relativity. One being for big objects and the other for microscopic one. In fact, standard model not seem to be all proven. Many particles are not...

Consider the internal energy of a gas and solid (different materials) both at the same temperature, which material has the larger potential energy and why? Do they also both have the same kinetic energy? Finally is the definition of temperature as the average kinetic energy of the particles only...

Homework Statement [ For a system of discrete point particles the energy momentum takes the form T_{\mu \nu} = \sum_a \frac{p_\mu^{(a)}p_\nu^{(a)}}{p^{0(a)}} \delta^{(3)}(\vec{x}-\vec{x}^{(a)}), where the index a labels the different particles. Show that, for a dense collection of particles...

Homework Statement Problem #13 on the attached picture (I can't retype a bubble diagram) Homework Equations I honestly have no clue. I know I'm not supposed to say this because I'm supposed to read my textbook first, but this is not covered at all in my textbook, this is a unit my teacher...

Just finished reading Sean Carroll's "The Higgs Boson and Beyond". I would be grateful if someone could explain how gravity, which I understand to be a function of mass, can interact with massless particles as evidenced by the phenomenon of gravitational lensing. I understand that gravity is a...

Hi, first of all I wan to ask a few simple questions , when we move a piece of wire perpendicular to a uniform magnetic field like between the faces of two magnets facing N-S we get a current either one or the other way in the wire , yet when we would shoot an electron beam the same path as the...

I wanted to ask something that should have been asked in the past... What are the chances to find a PhD in Astroparticle Physics [Experimental] if you have done something with LHC/ATLAS at your masters, mainly associated to data analysis and not hardware? Thanks.

Good day to all! I have a question : We have a flowing fluid ( liquid ) with known pressure, flow in the pipe ( pump is pumping it). There are some spherical microparticles in the liquid, let's say 10-15 microns. I want to create force to stop them moving! Will the pressure force be in the form...

Consider a system of two identical spin-1 particles. Find the spin states for this system that are symmetric or antisymmetric with respect to exchange of the two particles. (Problem 13.3, QUANTUM MECHANICS, David H. McIntyre) I know that for bosons, the total wavefunction should be symmetric...

I've been reading Jim Baggott's book "Higgs -- The Invention and Discovery of the 'God Particle' "and have a rather elementary question, easily answered, I'm sure, by folk that contribute to this forum: is the Higgs only associated with the inner machinations of other 'elementary' particles, or...

The question is simple, and I have checked the "similar discussions" and googled, but I still come out with various replies. I also know that experimental evidence that could back up the selected choice would be tricky, not to say impossible. But at least according to theory: the entangled...

I have been reading the Quantum Diaries here http://www.quantumdiaries.org/2011/03/25/an-idiosyncratic-introduction-to-the-higgs/ and in discussing the Higgs and the LHC experiment he says "The general problem is this: at the LHC, we’re smashing protons into one another. The protons are each...

Pardon me for asking a very simple question, but this is something that I'm confused about. If we have a pair of entangled particles, and we measure the state of one of the particles, then the state of the other particle becomes fixed instantaneously. But what if we have three entangled...

For example, can an electron and a photon become entangled?

This is a somewhat weird question, but here it goes: What would happen if there were only gravitons? Would some other kind of particle appear in the Universe sooner or later? Would there be any chance for mass to appear in such a Universe (assuming that the graviton is a massless particle)...

Is it possible for an entangled system of particles to be disentangled at a distance, without making them interact directly with each other?

The tital pretty much explains it all? Why would this be impossible or not explain everything?

Homework Statement A system of N distinguishable particles, each with two energy levels. The lower energy level has energy equal to zero, and the higher energy level has energy ##\epsilon##. The higher energy level is four fold degenerate. Calculate the heat capacity. Homework EquationsThe...

In a situation like this: What causes the particle/antiparticle pair to recombine? They obviously will have opposite charge, is there a virtual photon being exchanged between them that's omitted from Feynman diagrams? That would imply that it's mathematically irrelevant, I know than these...

Hello. It is said that if we exchange two electrons, we can't tell which is which. Identical mass, charge, etc. So if I hold two electrons, one in each hand, and someone switched them, I wouldn't be able to know. But one way to distinguish particles is their trajectory. If I have a very long 1D...

If you consider an electric dipole, why is it that there is any space between the two particles at all? If both particles of opposite sign attract to each other with equal magnitude, shouldn't they just stick together?

For example, if photons were the size of galaxies, would they still move at the speed of light?

Homework Statement A collection of charged particles move through a magnetic field at an angle to the field lines. Calculate the velocity of the particle if it is an electron moving at 30 degrees to the magnetic field of strength 3.4mT, causing it to experience a force of 4.7x106-18N Homework...

Can someone describe the physical processes which distinguish between separate and single particles when dealing with a collection of particles in the context of the De Broglie wavelength? The De Broglie wavelength is inversely proportional to the momentum of a "particle". Assume "separate"...

I understand the basic forces moving charges experience in magnetic fields. I dont; however, understand how these these charges would interact with particles uninfluenced by the magnetic field. 1. If a charged particle is moving perpendicular to a uniform magnetic field, it will follow a...

Hello all, I'm just learning about beta decay and the emission of beta particles. I have come to an understanding that this is ionising radiation because it has the ability to remove electrons and turn the molecules it interacts with into ions. I've looked on the Internet for this information...

Homework Statement Landau&Lifshitz Vol. Mechanics, p101 Q1 Find the moment of inertia of a collinear set of molecules Homework Equations I=sum m_i*(r_i^2) The Attempt at a Solution r_i= r_i'-r_cm where r_cm=sum m_i*r_i/sum m_i I=sum m_i r_i^2 I= 1/M sum m_i m_j (r_i' - r_cm)^2 I=1/M sum m_i...

Hello, could you please help me with this question? What particles do NOT have a dualistic character? Thank you for your answer.

Homework Statement There are three particles; 1) 26kg at 12i-hat 2)13kg at -5j-hat 3)13 kg at 5j-hat A) What is the gravitational force on the 26kg mass due to the 13kg mass at -5j-hat Homework Equations F= GMm/r^2 The Attempt at a Solution A) IN COMPONENTS; Y Component...

What home based solvent might dissolve an unknown electron microscope seen insoluble particles ? There are some sort of unknown insoluble particles in our water. Does anyone know of any home remedy acid solution (baking soda and vinegar) that might dissolve these particles ? Please keep in...

Were all the particles or matter a single particle in the beginning? If so were all forms of energy and and matter one single unit?

I'm practicing for the Physics GRE, and came across a question that has me stumped. "In elementary nuclear physics, we learn about the Fermi gas model of the nucleus. The Fermi energy for normal nuclear density (ρ0) is 38.4 MeV. Suppose that the nucleus is compressed, for example in a heavy ion...

Are virtual particles of the false vacuum during inflation indistinguishable from virtual particles of the true vacuum of the present universe?

Homework Statement A column of water contains fine metal particles of radius 20 nm, which are in thermal equilibrium at 25°C. If there are 1000 such particles per unit volume at a given height h0 in the water column, how many particles would be found in the same volume 1.0 mm higher than h0...