What is Particles: 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. Salmone

    I Strange Hamiltonian of two particles on the surface of a sphere

    I have a problem with this Hamiltonian: two identical particles of mass ##m## and spin half are constrained to move on the surface of a sphere of radius ##R##. Their Hamiltonian is ##H=\frac{1}{2}mR^2(L_1^2+L_2^2+\frac{1}{2}L_1L_2+\frac{1}{2}S_1S_2)##. By introducing the two operators...
  2. A

    I Energy reduction/deflection of beta particles due to isotope geometry

    Hello all. I'm an undergraduate student looking to conduct an experiment with an isotope that undergoes beta decay. I am curious as to the degree to which the isotope geometry will reduce the energy of/deflect beta particles emitted from the isotope. By geometry, I mean the "shape" of the...
  3. SR_0301

    I Statement about torque in a system of particles

    Hello guys, I’m studying Newton’s Mechanics at the first year of engineering, and I would like to ask one question about torque. In my book I found this statement ‘’ Given a system of particles, it’s always possible to determine a pair of forces which torque is indipedent from the pole chosen...
  4. Philip Koeck

    A Definition of entropy for indistinguishable and distinguishable particles

    I have a rather general question about the definition of entropy used in most textbooks: S = k ln Ω, where Ω is the number of available microstates. Boltzmann wrote W rather than Ω, and I believe this stood for probability (Wahrscheinlichkeit). Obviously this is not a number between 0 and 1, so...
  5. A

    I Deriving Special Relativity from Particle Indistinguishability

    Is it possible to derive special relativity from the principle of quantum mechanics according to which particles of the same type are indistinguishable? For example, if it is not possible to distinguish particles of the same type then particles colliding in a train at constant speed should...
  6. A

    MCNP6: Getting a "10 particles got lost" error

    MCNP6 gives me a "10 particles got lost" error when I try to run the attached input file modeling a 3x3 fuel lattice surrounded in coolant. As I understand it, this error is usually related to the geometry/surface definitions of each component, but I'm unsure of what the source of the error is...
  7. K

    I Number of ways to distribute particles

    Pathria, Statistical Mechanics " ... classical system composed of noninteracting particles... .Now, if there do not exist any spatial correlations among the particles, that is, if the probability of anyone of them being found in a particular region of the available space is completely...
  8. samy4408

    I Question about electromagnetics (waves and particles)

    I saw that we can talk about the light as particles (photons ) or as an electromagnetic wave , the question is that do we represent other electromagnetic waves (like microwaves or radio waves ) as particles (like we do with light ) ?
  9. O

    B Alpha Particles of Uranium 238

    I have a simple question. Do alpha particles from radiation arc and fall after leaving its source? Are these particles bound by the same gravitational laws as us?
  10. K

    I Schrodinger equation for N particles in a box

    [Pathria, statistical mechanics][1], pg2 ,when discussing ##N## particles in a volume ##V## "...there will be a large number of different ways in which the total energy E of the system can be distributed among the N particles constituting it. Each of these (different) ways specifies a...
  11. K

    I Form of potential operator of two interacting particles

    Considering two interacting particles in 3d, the corresponding Hilbert space ##H## is the tensor product of the two individual Hilbert spaces of the two particles. If the particle interaction is given by a potential ##V(\mathbf r_1 -\mathbf r_2)## ,what is the corresponding potential operator...
  12. AlonZ

    I E=hf for massive particles, but which Energy exactly?

    Hi there, I'm a bit confused about the E=hf equation for mass particle(f for frequency), and Lorentz Invariant (E^2 -p^2c^2=m^2c^4). The question is, which energy is it? Total Energy- Kinetic plus Rest, or only kinetic energy. Now, if it's total energy, then you get that a particle at rest...
  13. V

    Direction of of the velocity vector for particles in a sound wave

    Using the equations mentioned under this question, I came up with following analysis and directions of velocities on either side of ##x_1##. Also, I'm not sure if there is an easier qualitative way to know the velocity directions rather than do a detailed Calculus based analysis?
  14. A

    I Plasma-like Description for Elementary and Composite Quantum Particles

    My article has been published in Entropy . Abstract: Schrödinger noticed in 1952 that a scalar complex wave function can be made real by a gauge transformation. The author showed recently that one real function is also enough to describe matter in the Dirac equation in an arbitrary...
  15. Istiak

    Calculating Energy From Charged Particles: 0.5869 J

    Generally, energy is ##U=9\times 10^{9} \times \frac{5\times 10^{-6}30\times 10^{-6}}{2+(10+20)\times 10^{-2}}=0.5869 J## <br/> After touching, they have charges ##q_1 and q_2 = 35\mu C-q_1## ##\frac{q_1}{10}=\frac{35\mu C-q_1}{20}## I was wondering where 1/10 and 1/20 coefficients come...
  16. T

    COVID Mouthwash disaggregation of SARS-CoV-2 virus-like particles

    Disclaimer: This post is a 'Just-In-Case'; it is way out of my field and was not particularly impressed with the popular version. Others can better evaluate the research article. Mouth wash containing Cetylpyridinium chloride (a surfactant) does the job. Speculation is it may be a help in...
  17. H

    A Entangled particles in curved spacetime

    i do not know if the question about entangled particles has found mainstream answers; Suppose that pairs of maximally entangled particles are shared by Bob and Alice in a time independant gravitational field. Bob measures the spin in the direction of far fixed stars. There is a direction in...
  18. L

    Aerosol particles, how do I calculate this?

    Aerosol particles with an average diameter of 5 μm and a density of 1000 kg / m3 are spread to a room with a floor area of 20 m2 and a height of 3.5 m. How long does it take for all 5 μm particles to settle on the floor (dry deposition)? The answer should be 1 hour and 20 minutes.
  19. Usiia

    Self Study - Foundations of Electromagnetic Theory Problem 2-1 (two charged particles hanging on strings)

    I'd like someone to check that this solution is right, and if not, give me the point of failure and not the answer. Thanks!
  20. K

    I Equiprobability of Particles in an Isolated Box

    Suppose we've an isolated box having ##N## classical distinguishable particles in it, the box being hypothetically divided into two parts, left and right with both parts identical. Its said that the probability of having the configuration of ##n## particles in the left side is given as...
  21. Monsterboy

    Particles moving on a regular hexagon

    When I first read the question, it didn't occur to me that these particles would ever meet or catch up with their neighbors. They are all traveling from one vertex to another with a velocity ##v## and a distance ##a##, all either clockwise or anticlockwise right ? The question says "Each...
  22. S

    B Do charged particles always have spin?

    (Apologies for a basic question) Do charged particles always have spin ? Maybe a better question is, are charge and spin always associated ?
  23. rudransh verma

    When will the particles collide?

    I am stuck. Please ignore my handwriting. I am working on latex. All I am taking is x and y coordinates same of both particles. Yes they will meet at some time t.
  24. L

    I Experimental average lifetime of particles

    My professor said that if I take 10^24 particles, for example, and I observe them for 1 years, I can say that their average lifetime is at least 10^24 years. I am not able to understand why, I though the law of decay is N(t) = N0*e^(-ta), so if after 1 year N(t) = N0, I can say ta ~ 0 , so tau...
  25. neilparker62

    I Maximum Angle of Deflection for Colliding Particles

    When a heavier mass (or nucleus say) collides with a lighter one, it deflects through a certain angle which has a theoretical maximum. There are numerous derivations for this maximum angle of deflection ##(\sin\theta_{d_{max}}=m/M)## where m is the small mass and M the larger but none seem to...
  26. J

    Calculating the Probability of Particles Traveling Through Different Size Pores

    Homework Statement:: Not homework, but I want to calculate the probability of different size spheres traveling through different size pores. Relevant Equations:: V=4/3πr^3 volume of sphere. Volume of 60nm diameter particle = 1.13x10^5 nm^3. Volume of 70nm particle = 1.8x10^5 nm^3 Hi all, this...
  27. BillTre

    B Understanding Entangled Particles in Different Time Frames

    Here is something I don't understand which I expect someone here can explain. If one member of an entangled pair goes on a trip at relativistic speeds, there will be two different frames of observation, with two different elapsed times. The time frames can get off-set by years, over a long...
  28. Space

    B Particles Within Atoms: Uncovering the Mystery of Forces and Vacuum

    Transcript from "what the bleep do we know" the particles take up an insignificant amount of the-- of the volume of an atom or molecule, the fundamental particles. The rest of it is vacuum. Questions: If, inside of an atom is mostly space, how do we have stuff, that is made of atoms? Stuff...
  29. L

    I Is the current related to a path or to potential difference?

    The question is very simple: Is the flow of charge, or current, related to a closed path or there will be a potential difference without closed path to allowing the flow? I mean, If I have a battery that maintain 5V of potential difference through its terminal, I believe there is an amount of...
  30. F

    Potential Energy of three charged particles

    I set up an equation for the sum of all the potential energies and when cancelling out ##k## and ##q^2##, I got ##\frac{1}{0.05}-\frac{1}{x}-\frac{1}{0.05-x}=0##. However, this has no solutions, so I must've gone wrong somewhere. Could someone just give me a hint, not a solution, that would put...
  31. Viona

    Is my procedure for finding the S_z matrix correct?

    I have this homework: consider the case of two spin half particles. Use the basis: |++>, |+->, |-+>, |--> to find the matrices representing the operators S^2 and S_z. My idea for the solution for S_z is: S_z=S_z(1)+S_z(2) where S_z(1) is the operator for the first particle ... etc So I...
  32. R

    B Why exactly do Virtual Particles not violate Conservation of energy?

    Recently I've read more about virtual particles and at first I tought that there were only doubts that virtual particles are not interpretable with the help of uncertainty principle. Furthermore it can't be used an an "excuse" for the temporary violation of the conservation of energy. Can...
  33. snoopies622

    I On the meaning and mathematics of rotating spin 1/2 particles

    The other day I found a fascinating video on geometric algebra: At 34:50, after showing how to rotate a vector in three dimensions, he says, "wait a minute, this looks like a spinor from quantum mechanics. The way that spinors rotate is always said to be a part of so-called 'quantum...
  34. ergospherical

    I Understanding Papapetrou's Spinning Test Particles in GR

    I'd appreciate some clarification of this passage in the paper Spinning test particles in general relativity by Papapetrou, The definition is easy enough to understand, but what's the motivation? ##X^{\alpha}## are the coordinates of points on the worldline whilst ##x^{\alpha}## are...
  35. G

    I Usable energy from alpha particles?

    Please excuse my physics ignorance. Can usable energy be extracted from alpha particles? Perhaps in a manner similar to a photovoltaic panel producing power when exposed to light? Thank you.
  36. Ranku

    I What are the Misconceptions Surrounding Virtual Particles?

    Are the typical energies of virtual particles lower than real particles?
  37. R

    Angular momentum of a particles in the form of ##L = mr^2\omega##

    ##\vec{L} = \vec{P} \times\vec{r}## ##L = mvr sin \phi##, where P = mv Since ##\vec{r}## and ##\vec{v}## are always perpendicular, ##\phi## = 90. Then, ##L = mvr## At this point, I don't see how to get ##L = mvr = mr^2\omega##, using ##\omega = \dot{\phi}## I know that ##\omega =...
  38. Ebi Rogha

    I Uncertainty principle equation for virtual particles

  39. Huzaifa

    B Acceleration of Moving Particles: Explained

    I am not able to understand the following paragraph from my Physics textbook;
  40. Sciencemaster

    I Exploring Wave Function Collapse and Measuring Particles

    Hello! Let's say we have a wave function. Maybe it's in a potential well, maybe not, I think it's arbitrary here. This wave function is one-dimensional for now to keep things simple. Then, we use a device, maybe a photon emitter and detector system where the photon crosses paths with the wave...
  41. N

    B Why do moving charged particles feel a force in a magnetic field?

    When I read things about magnetism on internet, I don't understand at all about one thing: If a moving particle receive a force if it's in a magnetic field, so it should accelerate, so what happen if we change the referential so that the particle now don't move? The particle shouldn't receive...
  42. nomadreid

    I Entangled particles in black hole decay?

    First, I was not sure whether this should go into the Relativity or the Quantum Physics rubric, but since the central question is about entanglement, I opted for the Quantum. I do not have the necessary sophistication to follow string theory arguments, and even most explanations in...
  43. nonamebrand

    B Can particles interact without a mass?

    I recall reading someone questioning if it were possible for the higgs boson to be the primordial atom which led to the start of the universe. I was just wondering if that could even be possible, since the higgs field was zero and couldn't have given these particles any mass. (please be kind...
  44. sarahjohn

    Infinite Square Well with Multiple Particles

    Using the equation En = (h2*n2 ) / (8*m*L2), I got that E1 = 0.06017eV but the answer is not correct.
  45. Omega0

    B Distribution of particles, given a function

    I am not that super expert of statistics, so feel free to shift my formulation of the problem into the right one.First, for a physicist, the basic formulation of the problem. Let us say that you have a gravitational field and you have a fully symmetric problem on a flat world without other...
  46. brotherbobby

    Collision between two uniformly moving particles

    Problem : The statement is given above. Here I attach the image of the problem to the right. Attempt : (1) Condition for collision : For the two particles to collide, there should be no relative velocity perpendicular to their "separation vector" ##\boldsymbol{s}##. Hence, we must have ...
  47. I

    Chemistry Intermolecular forces between NO particles

    The answer is dipole-dipole and London dispersion forces, but I only chose London dispersion forces. How would you determine whether there is a large or small electronegativity difference between N and O? And therefore how would you determine whether the N-O bond is polar covalent or non polar...
  48. S

    MHB Mechanics- connected particles

    Two particles A and B are attached to the ends of a light inextensible string, which passes over a smooth pulley. Particle A has mass 8 kg and particle B has mass 5kg. Both the particles are held 1.2m above the ground. The system is released from rest and the particles move vertically. a) when...
  49. S

    MHB Mechanics- connected particles

    Two particles A and B are attached to the ends of a light inextensible string, which passes over a smooth pulley. Particle A has mass 8 kg and particle B has mass 5kg. Both the particles are held 1.2m above the ground. The system is released from rest and the particles move vertically. a) when...
  50. Ranku

    I N-body simulation of high or low-mass dark matter particles

    Do we notice any significant difference in distribution and dynamics of dark matter in galaxies when n-body simulations are done with high or low-mass dark matter particles?
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