Particles Definition and 1000 Threads

Homework Statement A particle A is suspended as shown in the figure by two strings, which pass over smooth pulleys, and are attached to particles B and C. At A, the strings are at right angles to each other, and make equal angles with the horizontal. If the mass of B is 1 kg, what are the...

How many as yet undiscovered particles do we need to make the standard model work?

Dear friends! If there are two particles of unequal masses in a system on which there are no external forces.When let free they collide under the influence of gravitation. Should they always collide at CM. If the system were under an external force of uniform gravitational field will the...

Homework Statement Please help; I've been attempting this question for days now and cannot get very far... I am desperate now Three identical particles X, Y, and Z of mass m are placed on a smooth horizontal table. X is joined to Y and Z by light (can be thought of as massless) inextensible...

All elementary particles, which are not made up by any other particles (electrons, quarks), are said to be zero dimensional and have no size. But why not? Are electrons literally zero dimensional particles with no size?

Homework Statement Good morning-afternoon. I have been tasked with solving the next exercice; but I am unable to spot the error. Please can anyone point me in the right direction?A)Calculate the thresold energy of a photon to disintegrate in an electron and a positron in the presence of an...

Homework Statement Figure 24-21 shows four pairs of charged particles with identical separations. (a) Rank the pairs according to their electric potential energy (that is, the energy of the two-particle system), greatest (most positive) first. (b) For each pair, if the separation between the...

Homework Statement Suppose teo particles with masses m1 and m2 enter a detector both with momentum p. Calculate the difference Δt of the times they need to cross a distance L. Suppose Δt can be measured with a 300 ps resolution. How long must L be if we want to distinguish particles with m1...

What are the mathematical relationships (if any) between the particles as described by Quantum Mechanics and the particles described by Quantum Field Theory? A specific question related to the general question above arose in post #14 of the thread: How can a particle be a combination of other...

Hi guys, I consider the qm-derivation of the electronic states of hydrogen. There are two different derivations (I consider only the coulomb-force): 1) the proton is very heavy, so one can neglect the movement 2) the proton moves a little bit, so one uses the relative mass ##\mu## The...

Hello everyone! I had a question about a particle (say a proton) with relativistic energies interacts with a magnetic field (in the z direction). As it is accelerates the particle emits synchrotron radiation. Naturally I assume that this emission of photons reduces the particle's energy. My...

Moderator's note: this is a spin off from a previous thread here. I confess to a very limited understanding of QM. I understand (somewhat) that a state of a particle can be a combination of possible states. I do not understand how a particle can be a combination of two particles. In...

Photon have the same size as an electron(i think) but no mass. Gluons also. WHY

Hi there, I am trying to find the number of fine particles (micron size) by obscuration. There are a light source and a photo-detector which particles are injected between them. I know the size of my particles. How can I find how many particles are passing through the light by obscuration of...

I am trying to solve the following problem for my graduate course in isotope geochemistry. If 1 g of 226Ra is separated from its decay products and then placed in a vessel, how much helium (cm3) will accumulate in the vessel in 60 days? Here is what I know. The decay series from 226Ra to Lead...

http://www.nature.com/news/not-quite-so-elementary-my-dear-electron-1.10471 Scientists have split an electron into 3 quasiparticles in the lab, why isn't this updated on the standard model?

Homework Statement Two particles, one with charge -7.13 × 10-6 C and one with charge 1.87 × 10-6 C, are 0.0284 meters apart. What is the magnitude of the force that one particle exerts on the other? Two new particles, which have identical positive charge q3, are placed the same 0.0284 meters...

Homework Statement Three particles, A, B, and C, with masses M, 2M, and 3M respectively, lie at rest in that order in a straight line on a smooth horizontal table. The particle A is then projected directly towards B with velocity U. Assuming the collisions are perfectly elastic, I need to find...

Suppose that you have N = \left(\frac{\partial U}{\partial \mu}\right)_{S,V} < 0, supposedly the number of particles, even though the actual number of particles is greater than zero. This means that you can have, in a system subjected to a grand canonical ensemble, less than 0 particle for...

Homework Statement A 2.5 MeV photon is moving in positive x-direction and an electron in the opposite direction at a velocity of 0.99c. Calculate their common total energy, momentum and total rest mass.Homework Equations Relativistic EquationsThe Attempt at a Solution I have some concerns...

Homework Statement A uranium-238 atom can break up into athorium-234 atom and a particle called an alpha particle, α-4. The numbers indicate the inertias of the atoms and the alpha particle in atomic mass units (1 amu = 1.66 × 10^−27 kg). When an uranium atom initially at rest breaks up, the...

It's been a little bit since I have studied multi-particle quantum mechanics and I am a little rusty on the notation. Let's say I have a wave function, that consists of the tensor product of two spaces, one for each particle moving, ##|\psi_1,\psi_2>##. Each of these particles is moving in a...

Hello everyone. Hopefully someone would be able to help me with this problem. The question states: Two point charges qa = -12 micro coulombs and qb = 45.0 micro coulombs and a third particle with unknown charge qc are located on the x axis. The particle qa is at the origin placed so that each...

Hello everyone, thanks for reading I'll explain my question. At first, light was described as electromagnetic waves, until Einstein proposed the photoelectric effect and thus creating the concept of photon, a particle of light with momentum and energy, but no mass. It could explain why the...

Homework Statement The figure depicts the motion of a particle moving along an x axis with a constant acceleration. The figure's vertical scaling is set by xs = 7.20 m. What are the (a) magnitude and (b) direction of the particle's acceleration ( +x or -x )? Homework Equations The Attempt...

What does the standard model have to say about the relationship between the total mass-energy of the universe and the characteristics of forces and force-carrier particles? That is, if the total mass-energy were different, would the nature, strength, … of the forces and force-carrier particles...

Homework Statement Two tugboats are pulling a barge. if the resultant of the forces exerted by the tugboats is a 5000-lb force directed along the axis of the barge, determine (a) the tension in each of the ropes, give then alpha = 45 (b) the value for alpha for which the tension in rope 2 is...

This is just a short question, it might have been asked already but I couldn't find anything. I read that we have attempted to reconcile the Casimir force with the observed expansion of the universe, doing this, we get a number 10^120 times too big. This is obviously a bad number to say the...

How Number of elementary particles in an atom are counted?

When the spin of an entanglement particle is established, it is said that the corresponding spin of its entangled twin is revealed immediately, (via wave collapse?), and that this interaction can occur across a substantial distance. It has also been said that this immediate interaction can occur...

Does an exchange of two identifical particles (electrons) lead to a new microscopic state?

Hi, i heard that as the universe will expand and the energy will grow sparse, in the end the matter itself will turn into radiation that will loose energy. So i wanted to ask, can a proton decay? and is it the same phenomenon as radioactive decay? Does it mean that even hydrogen (with no...

Hi all, I have a question about the ground state of an interacting quantum field theory. The state space in non-interacting QFT is a space where each field mode (with specified momentum p) has some occupation number n. These modes are interpreted as n particles with momentum p. The vacuum is...

Hello, it is my first post created in this forum :) I'm interested in physics of radiation burn. How does it work? In my opinion high-energy particles (like photons, neutrons etc.) leave their energy inside human body (for example breaking bonds in DNA). This event trigger primary electrons...

From what I can recall the shape of tracks of particle accelerator is circular. Is it possible to change this circular shape in future particle acclerators, to shapes like some knots (with more than one crossing)? to gain more distance in less space, I don't know how construct it, but it's a...

Random thought... Is it possible for a charged particle to travel fast enough, or simply enter a magnetic field at just the right time in the magnetic wave's cycle, to pass through the magnetic field unaffected? If so, what is that calculation. If not, why not. Roy

When I read about string theory, I sometimes get a feeling that the pointlike nature of particles in QFT is a problem that needs to be fixed, but I have never seen an explanation of the problem. Is this correct, and if so, why? Point in case (from https://en.wikipedia.org/wiki/String_theory)...

What is so unstable about one particle that it only lasts a billionth of a second? Opposed to another particle that lasts much longer. What is so different between the two and why are there "timers" set when these particles created?

What particles that constitute the black holes?Does normal particles constitute the black holes? How can we calculate the ratio of types of particles in the universe(we consider known matter but not consider dark energy and dark matter)?How can we calculate the total number of particles in the...

Assuming that a massive spin-1 particle has momentum only in the z-direction, the polarization vectors are given by \varepsilon_{\mu}(J_z = +1) = (0,-\frac{1}{\sqrt{2}},-\frac{i}{\sqrt{2}},0 ) \varepsilon_{\mu}(J_z = 0) = (\frac{p}{m},0,0, \frac{E}{m}) \varepsilon_{\mu}(J_z = -1) =...

If we measure the location of an electron in atom once and then again instantly, we would cause the collapse of the wave-function twice in some time interval and the object has a probability of being in a distanced location in regard to the location of previous measure (for example, we measure...

Homework Statement Can the equation E = pc be applied to particles? Why or why not?Homework EquationsThe Attempt at a Solution It can be applied to particles that DONT have a rest mass (photons, which are particles). It can not be applied to particles that have a rest mass (almost everything).

Homework Statement Explain the circumstances that enable a particle to move un-deflected with uniform motion through an electric field if it is given an initial velocity perpendicular to the electric field. Assume the electric field is the only field present.[/B] Homework EquationsThe Attempt...

Homework Statement 1) Describe and explain what happens to the electron beam on the screen of a teltron tube as the EHT(electrical high tension) voltage increases from 3000V to 3500V. 2)What is the effect of E field on light waves? Homework EquationsThe Attempt at a Solution 1) The beam...

Is it possible that fundamental point like particles (ie electrons) are actually particles with shape size and structure that are too small for any of our current technology to detect?

We have been able to explain the reason for the mass of a particle to a great extend... But till now why are we not getting a clear idea of why does a particle has charge?? What gives a particle its charge??

There are exotic atoms such as the protonium (proton+antiproton) and positronium (electron+positron); I was wondering if quark-antiquark particles could appear even if they only exist for a fraction of a second.

Is it possible that they have the structure something like we used to picture them as? For example, what if we captured an electron and zoom in with a microscope that see infinitly small distances. Is it possible that if we zoomed into the electron close enough that we would see an object...

Hi simple question here, I was wondering if matter (actual particles) are lost from the fusion process.

I don't have clear how two particles initially "independent" in the sense of "not entangled" become then entangled because of their mutual interaction (and in this last case, when and how I can say they "interact"?). How do I know how should they approach or how strong their interaction should...