What is Particle: Definition and 1000 Discussions

In the physical sciences, a particle (or corpuscule in older texts) is a small localized object to which can be ascribed several physical or chemical properties such as volume, density or mass. They vary greatly in size or quantity, from subatomic particles like the electron, to microscopic particles like atoms and molecules, to macroscopic particles like powders and other granular materials. Particles can also be used to create scientific models of even larger objects depending on their density, such as humans moving in a crowd or celestial bodies in motion.
The term 'particle' is rather general in meaning, and is refined as needed by various scientific fields. Anything that is composed of particles may be referred to as being particulate. However, the noun 'particulate' is most frequently used to refer to pollutants in the Earth's atmosphere, which are a suspension of unconnected particles, rather than a connected particle aggregation.

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  1. P

    I Identify the charge and strangeness of particle Y

    Ive included question and thinking in the attachments. Many Thanks
  2. W

    Lagrange Equations of Motion for a particle in a vessel

    The final answer should have a negative b^2⋅r(dot)^2⋅r term but I have no idea how that term would become negative. Also I know for a fact that my Lagrangian is correct.
  3. W

    Lagrange Equations of Motion for a particle in a vessel

    I start out by substituting rcos(Θ) and rsin(Θ) for x and y respectively. This gives me z=(b/2)r^2. The Lagrangian of this system is (1/2)m(rdot^2+r^2⋅Θdot^2+zdot^2)-mgz. (rdot and such is the time derivative of said variable). I then find the time derivative of z, giving me zdot=br⋅rdot and...
  4. GeolPhysics

    I Schrodinger equation for a free particle in 3d space

    I've got the solution to the question but I just need more detail. I can't work out the first step of the solution to the second step. That should read, I don't know what they multiplied ih-bar by to make it (i/h-bar)^2?
  5. warhammer

    Classical Physics & Particle Motion Under Force Field

    The particle is moving under a force field with the potential energy equation described above. I find it logical that Newton's Laws can be used as in the question itself it is stated that the velocity is quite small and we could approximate its subsequent motion via the notions of Classical...
  6. A

    I Why simultaneous detection of wave and particle nature is not possible

    We have been taught that the there is no experiment designed to detect wave and particle nature of light simultaneously. Also, that light propagates by the virtue of its wave nature and interacts by the virtue of its particle nature. let us take an electron beam passing through two slits...
  7. F

    Calculating Net Force of Particle 5: A Problem Overview

    I have the following problem: So, I know the following: ##q_1 = -e## ##q_2 = -e## ##q_4 = -e## ##q_5 = e## ##e = 1.6*10^{-19}## ##k = 9*10^{9}## Now, I can get the current ##F_{net}## of particle 5 with this information: ##F_{net} = (F_{3} - F_{1})\hat i + (F_{2} + F_{4})\hat j## ##F_{1} = k...
  8. L

    A Timescale of virtual photon interaction in particle scattering

    I'm studying the electron-proton deep inelastic scattering. In the notes that I'm studying from the author states that the time-scale for a virtual photon to interact with a proton is ##τ\sim\frac{1}{Q}##, where ##Q## is the momentum transfer with ##Q\gg M##, which is the mass of the proton. I...
  9. A

    Electric Field for the circular path of a positively charged particle

    Here is picture. Answers is A. My attempt was that I thought if i were to place a positive test charge then it would go from top to bottom if there was a positive charge in the center it was avoiding and a positively charged particle at the top, but an electron at the bottom so it would avoid...
  10. A

    Bubble chamber experiment on a K− beam

    Hello everybody! Let's begin with the spin. Spin of the ##\Lambda## is ##1/2## and of the pion is ##0##: $$ \frac{1}{2} \otimes 0 = \frac{1}{2}$$ Since I know from the homework statement that ##L=1##: $$ \textbf{J} = \textbf{spin} \otimes \textbf{L} = \frac{1}{2} \otimes 1 = \frac{1}{2} \oplus...
  11. S

    I Is there such a thing as a gamma particle?

    OK, I understand that a gamma ray is just an electromagnetic wave, and so a gamma particle could be a photon, but somehow I think that the author here is not being that sophisticated: https://www.theatlantic.com/magazine/archive/2019/09/why-are-washing-machines-learning-to-play-the-harp/594706
  12. B

    Where is a particle most likely to be? (Griffiths Quantum Mechanics)

    The wave function described seems impossible. Wave functions have to be differentiable at all points, right? Otherwise they don't represent a physically realizable state. The wave function in the example isn't differentiable at x=A, the maximum point. Also, for problem (c), I know it's visually...
  13. E

    B When to think of PE as property of a system vs of a particle

    This is a bit of a vague question, but I was wondering if someone could explain. As far as I know, potential energy is formally a property of a system (for instance, the GPE of two gravitationally attracting particles). In many physics problems it happens to be the case that one of the bodies...
  14. S_Wildjocks

    Forces acting on a magnet which is deflecting a charged particle

    Summary: Considering a charged particle moving through a magnetic field, what forces does the particle exert on the magnet that is causing it to deflect? Hi all, probably a dumb question, but what force(s) does a charged particle exert on a magnet as it passes through it's magnetic field and...
  15. DaynaClarke

    Total Particle Energy Flux in Auroral Arcs

    Homework Statement: Consider electron precipitating vertically into an auroral arc of area 1.0 km x 1200 km in the horizontal plane. The energy of the electrons is equal to 5 keV and the electron flux is 8.0 x 10^13 m^-2 s^-1. Determine the total particle energy into the arc, the total current...
  16. dRic2

    I Can a free particle have a definite energy in quantum mechanics?

    It's been a long time since my last exam on QM, so now I'm struggling with some basic concept that clearly I didn't understand very well. 1) The Sch. Eq for a free particle is ##-\frac {\hbar}{2m} \frac {\partial ^2 \psi}{\partial x^2} = E \psi## and the solutions are plane waves of the form...
  17. Q

    A Particle production in 1+1D QFT

    I am currently studying the Massive Thirring Model (MTM) with the Lagrangian $$ \mathcal{L} = \imath {\bar{\Psi}} (\gamma^\mu {\partial}_\mu - m_0 )\Psi - \frac{1}{2}g: \left( \bar{\Psi} \gamma_\mu \Psi \right)\left( \bar{\Psi} \gamma^\mu \Psi \right): . $$ and Hamiltonian $$ \int \mathrm{d}x...
  18. H

    I How to collapse a water wave through a double slit into particle behaviour?

    Electrons passing through a double slit is in a superposition of passing through the left slit and the right slit, thereby producing an interference pattern on the screen. But when a detector is placed to detect which slit the electrons pass through, the interference pattern is destroyed. How...
  19. mPlummers

    I How to find the most likely modes of decay for a particle

    What are the most likely modes of decay for ##\Omega ^{-}## into 2 hadrons? ##BR_{k}=\frac{\Gamma _{k}}{\Gamma}## ##\Gamma=\frac{\hbar}{\tau }## ##\Gamma _{k}=\Gamma _{if}=2\pi \rho|<\Psi _{i}|H_{Int}|\Psi _{f}>|^{2} (E_{f})## I took a look at the Particle Data Group, and the most likely modes...
  20. A

    Quantum numbers of a system of particles

    Hello everybody! I have a problem with this exercise when I have to find the possible angular momentum. Since ##\rho^0 \rho^0## are two identical bosons, their wave function must be symmetric under exchange. $$(exchange)\psi_{\rho\rho} = (exchange) \psi_{space} \psi_{isospin} \psi_{spin} =...
  21. A

    Solving Muon Momentum Decay: Maximizing Expression & Intuition

    My first idea was to find an expression of the muon momentum as a function of the angle and then maximaze the expression. But my attempts were not succesful. I report here my attempt. Set up (referring to the attached file "bettini.pdf"): $$ p = (\sqrt{p_k^2+m_k^2},0,0,p_k)$$ $$ k_1 =...
  22. S

    When does the particle fall off the dome

    A particle was resting on top of a dome and given a negligible push such that it falls. The question is at what angle will the particle fall off the dome. The solution is that, m\frac{v^2}{a} = mg\cos\theta - R and by conservation of energy 0 + mga = \frac{1}{2}mv^2 + mga\cos\theta then the...
  23. A. Neumaier

    I Wave-particle duality revisited: Neither wave nor particle

    Jan Sperling et al., Wave-particle duality revisited: Neither wave nor particle, arXiv:1907.09836 From the abstract:
  24. G

    Determination of the velocity of a particle in a hollow cone

    Hi, please could I ask for help with the following question: A smooth hollow circular cone of semi-angle α, is fixed with its axis vertical and its vertex A downwards. A particle P, of mass m, moving with constant speed V, decribes a horizontal circle on the inner surface of the cone in a plane...
  25. M

    Calculate the energy release of an atom

    First of, I have no idea what I'm supposed to do with the neutrinos and the photons. Can somebody explain how to handle these? The rest of what I tried is quite straight forward $$\begin{align*}\Delta E &= 4M_p - M_{He} - 2 M_e + E_{\text{Neutrino and Photons}}\\&= 4M_p - (2[M_p+M_n]-E_B) - 2...
  26. CricK0es

    Separation of variables: Context of decelerating charged particle

    Attempted rewriting acceleration, a, in terms of dv/dt and then separating variables to integrate. This didn’t work... So then I remembered that my gamma factor is also a function of v (!), but then I think I would be required to play around with integration by parts, which seems overly...
  27. M

    I Faster Than Light Particle: Could it Create the Universe?

    I've wondered what would happen to a particle if it could break through the 186,000 miles/second speed barrier and go faster than light. Would it go say 186,001 miles/second or would it go infinitely fast. I know Einsteins Special Relativity prohibits this but I have just wondered. Now if this...
  28. D

    I Realistic Time Dilation for Objects > Subatomic Particles

    Time travel, or more precisely time dilation, has been a well known proven result of Relativity. It has been demonstrated most notably in satellites traveling thousands of mph around the world with GPS. You can only go forward with our current understanding of physics. Have there been any...
  29. I

    I Exploring Particle Spin and Bell's Inequality

    I know there are numerous threads on this and I have read quite a bit such as EPR and Bell's inequality. I hope I can ask this the right way: A particle has 0 spin and gives off two children particles with spins -1/2 and +1/2 (we don't know which is which yet, or they have to end up this way...
  30. Cyclone Charlie

    Particle in a magnetic field -- question

    I went with R=mv/qb, thus -> 6.64e-27*35.6e3/2*1.6e-19*1.8, and got 4.1e-4 m (metres), so diameter is 2R, 8.2e-4 m, as an answer, the reference site gives 3.95e+10 m as the answer, who's right here?
  31. G

    Relativistic charged particle in a constant, uniform EM field

    I have to find pμ(τ) of a particle of mass m and charge q with v(0) = (vx(0), vy(0), vz(0)) in a electric field E parallel to the y-axis and a magnetic field B parallel to z axis, both constant and uniform, with E = B. Here follows what I have done (see pictures below): I wrote 4 differential...
  32. L

    Is a particle beam or laser beam conductive?

    If particle beam or laser beam weapon would be used to cut the electrical wires in high voltage transmission lines of the enemy. Could the current conducts into the particle beam (or laser beam) itself and can short circuit in the weapon platform? I know ionized air can conduct electricity...
  33. L

    I Particle Accelerator with the Earth's diameter

    If particle accelerators with circumference of the Earth could be built (imagine around the world). How many TeV can it reach? Maybe new physics can occur at 2000 TeV. I heard the US nuclear arsenals costs 2 trillion dollars. Worldwide, the total costs of all nations nuclear arsenals may reach...
  34. amjad-sh

    Python Calculating Spin-Loss of a Particle Using Integral Form

    The integral has the form: $$\frac{s^2\nu^4}{(2\pi)^2}\int_{-1}^1 u(1-u^2)k_f^5[|r_1\chi_1|^2+|r_1\chi_2|^2-|r_1|^2\chi_1^*\chi_2\cos(2k_f\sqrt{u^2-\nu^2}a)-|r_1|^2\chi_2^*\chi_1cos(2k_f\sqrt{u^2-\nu^2}a)]\, du$$ ##r_1,\chi_1## and ##\chi_2## are also imaginary functions of u, because the form...
  35. G

    On the motion of a particle on the inner surface of a sphere

    Could anyone please help me out with the second part of this question: I've got the first part, u = √(5ga) Here's my diagram for the second part: Distance traveled is from bottom of sphere to peg is 2πa/3 which means angle traveled is 2π/3. So the particlee is going to travel 2π/3 radians...
  36. IonReactor

    A (Plasma Physics) Spatial uniformity of particle species

    Early in Bellan he asks us to consider a finite-temperature plasma and assume that the ion and electron densities are initially equal and spatially uniform. He approaches the problem of calculating the Debye length by considering each species of particle, σ , as being a fluid so that the...
  37. Anonymous1212144

    B Probability of finding a particle

    Let's say that I observed a free particle at a certain location. Is there any way I can calculate the probability of finding that same particle at another location when I look for it again?
  38. M

    B Particle Deceleration in Relativistic Jets?

    I have a question about this picture: It shows matter traveling at relativistic velocities away from a black hole: "Figure 5.21: This VLA image of the radio-loud quasar 3C 175 shows the core, an apparently one-sided jet, and two radio lobes with hot spots of comparable flux densities. The jet...
  39. FourEyedRaven

    Particle Thomson (Modern Particle Physics) & Schwartz (Quantum Field Theory)

    Hi. Are these two books complementary, or do they have too much in common? https://www.amazon.com/dp/1107034264/?tag=pfamazon01-20 www.amazon.com/Quantum-Field-Theory-Standard-Model/dp/1107034736/ My problem is that I still don't quite understand the difference between university courses in...
  40. F

    Strong Nuclear Force & Particle Accelerators

    I am a teacher and the problem statement is part of our curriculum. I feel like I have a basic understanding of what particle accelerators are, but I only have a vague idea of what the strong nuclear force has to do with this. Here's what I know: In a particle accelerator, you might smash...
  41. QuasarBoy543298

    I Particle in free space - what happens to the wave function after measurement?

    If I'm trying to solve the problem of a particle in free space (H = P2/2m ). the eigenfunctions of the Hamiltonian cannot be normalized. now assume I have a legitimate wave function expressed in terms of the eigenfunction of H and I want to measure its energy. what will happen to the...
  42. Physics lover

    Motion of a particle in a uniform magnetic field

    All i could think is that the z component of velocity will remain unchnged as there is no force in that direction.And for the x and y component can we imagine the helical motion as a superposition of a circle and a straight line.So for x and y component can we solve for a particle moving in a...
  43. D

    Kinematics problem -- A particle is moving with changing acceleration....

    A particle, P, starts from rest at a point X and moves in a straight line with an acceleration expressed as a=4t. After 2 seconds, the particle reaches Y and it stops accelerating. The particle leaves Y with a velocity -3ms-1, and finally comes to rest at Z. (i) Find the value of t when the...
  44. W

    How Does Conservation of Momentum Apply to Particle Decay?

    Attempt at solution: By conservation of momentum: $$P = (M,0,0,0) = p_1 + p_2 = (E_1 + E_2, 0, 0,0)$$ thus $$ M = E_1 + E_2 = 2k^2 + m_1^2 + m_2^2$$ Now $$E_1^2 - E_2^2 = m_1^2 - m_2^2 = (m_1 + m_2)(m_1-m_2)$$ $$ = M(m_1-m_2) = (2k^2+m_1^2+m_2^2)(m_1-m_2)$$ Isolating k: $$ k =...
  45. W

    I Uncertainty Principle in the context of tracking particle paths

    I have a bit of confusion regarding the application of the uncertainty principle in the context of experiments. If a detector allows you to measure a particle's path through said detector, does that mean that you know a particle's position at all points in time, and are able to work out its...
  46. H

    I Calculate the number of states for a particle in a box

    The multiplicity of states for a particle in a box is proportional to the product of the volume of the box and the surface area of momentum space. $$ \Omega = V_{volume}V_{momentum}$$ The surface area in momentum space is given by the equation: $$p^{2}_{x}+ {p}^{2}_{y}+{p}^{2}_{z} =...
  47. sergiokapone

    I Covariant derivative of the contracted energy-momentum tensor of a particle

    The energy-momentum tensor of a free particle with mass ##m## moving along its worldline ##x^\mu (\tau )## is \begin{equation} T^{\mu\nu}(y^\sigma)=m\int d \tau \frac{\delta^{(4) }(y^\sigma-x^\sigma(\tau ))}{\sqrt{-g}}\frac{dx^\mu}{d\tau}\frac{dx^\nu}{d\tau}. \end{equation} Let contract...
  48. sergiokapone

    I Derivation of Geodesics Eq from EM Tensor of Point Particle

    The energy-momentum tensor of a free particle with mass ##m## moving along its worldline ##x^\mu (\tau )## is \begin{equation} T^{\mu\nu}(y^\sigma)=m\int d \tau \frac{\delta^{(4) }(y^\sigma-x^\sigma(\tau ))}{\sqrt{-g}}\frac{dx^\mu}{d\tau}\frac{dx^\nu}{d\tau}.\tag{2} \end{equation} The covariant...
  49. R

    I Lagrangian for a free particle

    In Landau mechanics it's been given that multiple Lagrangians can be defined for a system which differ by a total derivative of a function. This statement is further used for the following discussion. I understand that the term for L has been expanded as a Taylor series but I can't understand...
  50. F

    A Why do we know that an elementary particle is a point particle?

    Elementary particle can be consider as a "wave packet" of the field,but a "packet" of field must have a size.Why do we know elementary particle is point particle?
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