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. Vitani11

    How to find the force exerted on a particle on the Earth by the Sun

    Homework Statement Find the force exerted on a particle on the Earth by the sun. Homework Equations F = - GMm/r2 r = distance between sun and particle M = mass of sun G = Gravitational constant m = ? The Attempt at a Solution Should I be using the other mass as that of the earth, or that of...
  2. P

    Electron to Stationary Proton Collision

    Homework Statement A 2 GeV electron is incident on proton (m_p * C^2 = 0.938 GeV) target at rest. Calculate the invariant mass of the electron-proton pair in the Center of Mass(CM) frame. Neglect the mass of electron which is much less than the proton mass.Homework Equations M = [P1 + P2)][/2]...
  3. S

    A Identification of particle and antiparticle in lagrangian

    Lagrangians that include a particle field and its corresponding antiparticle field always have the particle field and the antiparticle field in the same terms. For example, in the theory of a complex scalar boson ##\phi##, the Lagrangian is a function of ##\phi^{*}\phi##, and not of ##\phi##...
  4. Mister T

    Kinetic Energy and Momentum of a Relativistic Particle

    College-level introductory physics textbooks usually devote a chapter to special relativity. Peter J. Riggs in his article appearing in the February 2016 issue of The Physics Teacher (pp 80-82) derives a couple of expressions for the kinetic energy of a massive (as opposed to massless) particle...
  5. A

    I Unruh effect, temperature and particle density....

    Hi all, This is a followup to a question I asked a number of years ago about the Unruh effect. I understand that an accelerated observer will see warm gas of particles following a blackbody distribution with some temperature T, where as an inertial observer would see none. My question is: how...
  6. R

    B Possible for a particle to diffract around a barrier

    According to quantum theory it is possible for a particle to diffract around a barrier. Does this explain why I often seem to completely miss a tennis ball? Explain why or why not?
  7. Funner

    Electrostatic force on polymer particle in an electric field

    Hi there, in electrospinning, a positive charge of around 10.000Volt is applied to a needle, where a viscous polymer is extruded. There is a grounded collector in a distance of 15mm and the established electrical field generates electrostatic forces and draws a thin polymer jet to the...
  8. I

    I Why does the existence of the Higgs Field require a Higgs Particle?

    I believe I understand how the Higgs field imparts "mass" on a particle. Would someone explain how the existence of the Higgs Field means there has to be a Higgs Particle?
  9. J

    What is the basic math to understand particle physics?

    Hello folks. What math do I need to understand books talking about quark-antiquark pairs, the Higgs field, and the Standard Model?
  10. M

    B The most fundamental "particle"

    Hi, Are there any fundamental "particles" that has no charge (e.g. color charge, electric charge, etc.), mass, volume and spin?
  11. Mihai_B

    I Solve Electromagnetic Field Acting on Charged Particle

    Can anyone help me find any mistake in this expansion ? (I've asked it also in other places but I got no answer)) Pα= e Fαβ Uβ c = speed of light m = "rest" mass e = charge a = sqr(1 - v2/c2) v2 = vx2 + vy2 + vz2 dτ = dt a (proper time) momentum 4 vector : Pα = [mc/a , mvx/a , mvy/a ...
  12. T

    Magnitude of average force exerted by each particle on other

    Homework Statement A particle of mass 5.0kg travels initially with a velocity of 8.0m/sˆı and then interacts with a particle of mass 6.0kg which was initially at rest. After the interaction the 5.0kg mass travels at a speed of 4.0m along a direction which makes an angle of 53◦ with the x-axis...
  13. ChrisisC

    B How does Partcle Symmetry affect the way a Particle Behaves?

    How does a particles symmetry effect the way it behaves? Do particles with similar symmetry interact with each other in a special way than 2 particles with different symmetries?
  14. Selveste

    Particle distribution, Diffusion

    Homework Statement An initial particle distribution n(r, t) is distributed along an infinite line along the z-axis in a coordinate system. The particle distribution is let go and spreads out from this line. a) How likely is it to find a particle on a circle with distance r from the z-axis at...
  15. gkamal

    Consider a particle moving through magnetic field(T/F)

    Homework Statement [/B]Homework Equations F= qvbThe Attempt at a Solution [/B] I tried FTTT and FTFT but both were wrong , i know that the acceleration is in the same direction as the force , but how come the other 3 are not all true.By the right hand rule shouldn't the force be...
  16. gkamal

    Direction of Charged particle in magnetic field

    Homework Statement Homework Equations F= q v x B The Attempt at a Solution [/B] I tried using the right hand rule to find the direction of the force and seeing if the particle curves that way or not but obviously that's wrong
  17. ChrisisC

    B Can a point-like particle really exist in a 0-dimensional universe?

    How is it possible that a point like particle is 0 dimensional? Could it only exist within pure mathematics? or actually exist physically in our universe?
  18. S

    I Gauge invariance of momentum of charged particle

    I know that, in the presence of a magnetic field, the momentum of a charge particle changes from ##p_{i}## to ##\pi_{i}\equiv p_{i}+eA_{i}##, where ##e## is the charge of the particle. I was wondering if this definition of momentum is gauge-invariant? How about ##\tilde{\pi}_{i}=p_{i}-eA_{i}##?
  19. Dishsoap

    Particle movement in inhomogeneous magnetic field

    Homework Statement Show that for the case of a general inhomogeneous magnetic field, $$\dot{\vec{v}}=\frac{e}{2mc} (\vec{v} \times \vec{B} - \vec{B} \times {v})$$ The attempt at a solution I think I am oversimplifying things. I used that, for an electron in a magnetic field, m \frac{d...
  20. Fasso

    I Probability of Particle Collision on a Closed Surface

    Is it more probable that particles will collide if both are moving or if one has velocity equal to 0? Let's say we don't have any forces between them and they're on a closed surface (for example a square).
  21. Vitani11

    Finding the probability to find a particle in a well

    Homework Statement A particle is in the n = 1 state of an infinite square well of size L. T. What is the probability to find the particle in the region Δx = 0.007L at the point x = L/2? 3L/4? (Since Δx is small you don't need to do any integration) Homework Equations ψ = Δxf(x) Δx = 0.007L...
  22. T

    I Entangled particle on a nanoprobe.

    One entangled particle held on a light sail nanoprobe sent to our nearest star, the other entangled particle in a lab on earth. Could this possibly provide instantaneous communication?
  23. S

    I Lie Algebra in Particle Physics simplified

    Hello! Is there any rule to do sums and products like the one in the attached picture (Lie.png) without going through all the math theory behind? I understand the first (product) and last (sum) terms, but I am not sure I understand how you go from one to another. Thank you!
  24. S

    A Transverse polarizations of a massless spin 1 particle

    Physical polarization vectors are transverse, ##p\cdot{\epsilon}=0##, where ##p## is the momentum of a photon and ##\epsilon## is a polarization vector. Physical polarization vectors are unchanged under a gauge transformation ##\epsilon + a\cdot{p}=\epsilon##, where ##a## is some arbitrary...
  25. J

    Kinetic Energy of a Particle in a semi-spherical bowl

    Homework Statement A 410 g particle in a semi-spherical bowl of radius 0.9 m is released from rest at point A at the level of the center of the bowl, and the surface of the bowl is rough. The speed of the particle at B is 2.6 m/s. The acceleration of gravity is 9.8 m/s 2 . What is its kinetic...
  26. AndresPB

    I Acceleration of a Particle Because of a Wave

    Hello all, I would like to know why an electron is accelerated in a linear accelerator because of the microwaves emitted by a magnetron?. Can someone tell me what are the relevant physics equations and what is the role of skin-effect here? Thanks a lot.
  27. S

    B Particle Uniformity: Are All Particles Alike?

    I was wondering if all particles of a given type are considered to be exactly alike.
  28. Isomorphism

    Particle decay: Relativistic or classical?

    This question was asked in an competitive exam in India. The relevant equations are momentum conservation in the classical sense and the 4 momentum conservation. My attempt: Classical momentum conservation would seem inaccurate since the kinetic energies are high. However, a straightforward...
  29. moenste

    KE of alpha particle using integer values of nuclear masses

    Homework Statement (a) Cobalt has only one stable isotope, 59Co. What form of radioactive decay would you expect the isotope 60Co to undergo? Give a reason for your answer. (b) The radioactive nuclei 21084Po emit alpha particles of a single energy, the product nuclei being 20682Pb. (b) (i)...
  30. K

    B Particle Physics: Pions Produced via Strong & Weak Interaction

    We know that pions can be produced through decaying of kaons via weak interaction, but we also know in the acclerator the pions can be produced in pair via strong interaction. So my question is pions are produced via both strong and weak interactions?
  31. I

    Cooling and its effect on particle speed

    Hi, I know and understand that heating a system causes the particles inside to increase in kinetic energy, due to the conservation of energy. What I don't understand is how does cooling a system causes the kinetic energy of the particles to slow down. Like how does cooling from sources such as...
  32. A

    Find the speed of the particle after 0.2 seconds

    Homework Statement The particle is thrown horizontally with speed 10 m/S (I believe from a height). Find the speed of it after 0.2 seconds. Homework Equations vx=v vy=gt v=sqrt(vx^2+vy^2)[/B] The Attempt at a Solution vx=10 vy=10*0.2=2 v=sqrt(100+4)=10.198m/S Am i right?
  33. G

    Finding the time period using the potential

    Homework Statement A particle of unit mass moves in one dimension with potential V(x) = ½μ2x2 + εx4 (ε>0). Discuss the motion of the particle. If the particle released from rest at x=a (a>0) express the time period T for the particle to return to a in the form of an integral and show that when...
  34. quantumfunction

    B Do we measure the particle or the wavefunction?

    It seems to me that we don't measure a particle because a particle doesn't have an objective existence independent of the wave function or does it? The wave function in this case would have to be real because you can't have probability without the underlying possibility of a specific outcome...
  35. N

    B Quantum Mechanics: Wave-Particle Duality Explained

    Hi, i am doing an introductory course in quantum mechanics (that would be equal to first two chapters in griffith's quantum mechanics). I have the doubt that what exactly do we consider in quantum mechanics. Let me say like the electron is a particle and when we will observe it will have a...
  36. K

    Kinematics of a Thrown Ball: Finding Time to Reach Ground

    Homework Statement A ball is thrown horizontally wit speed 20m/s, from the top of the building which is 30m high. Find the time the ball takes to reach the ground? Homework Equations S= ut+0.5at^2 The Attempt at a Solution S=-30 u=0 A=9.8 T=? When I pluck the values I will get t^s=-30/4.9...
  37. M

    Stokes Number for Particle Motion?

    Hello, I have a question... With the Stokes Number you can derive if particles follow a streamline or not, right? Let's say I am in a windtunnel, the wind is coming from the east. And I have a tube in the wind tunnel (horizontally located) which is 180° opposite to the flow (the opening of the...
  38. Vitani11

    Find the force of attraction for a particle outside sphere

    Homework Statement A sphere of radius R contains two spherical cavities. Each cavity has a radius of R/2 and touches both the outside surface of the sphere and its center as shown. The mass of a similar sphere without the cavities is M. Find the force of attraction on a small particle of mass m...
  39. D

    Solve Infinite Square Well Homework: Find Energy, Probability

    Homework Statement ISW walls at 0 and L, wavefunction ψ(x) = { A for x<L/2; -A for x>L/2. Find the lowest possible energy and the probability to measure it? Homework Equations Schrodinger equation ψ(x)=(√2/L)*(sin(nπx/L) cn=√(2/a)∫sin(nπx/L)dx {0<x<a} En=n2π2ħ2/2ma2 The Attempt at a...
  40. H

    B Does tunneling affect the energy of a particle in a finite box?

    using alpha decay as a concrete example is the energy of the alpha inside and outside the nucleus the same. it appears so from what I can see but alphas do have a range of energies usually up to between 4 - 9Mev. which is the same range as inside the nucleus. my question really is does...
  41. Armando Valle

    A How can i build a homemade particle accelerator?

    Hello people, i was thinking about building a homemade particle accelerator but i do not know the materials and specifications to build one, can you guys help me know what thing do i need to buy and how to make one? Thanks
  42. Konte

    I Quantum thermodynamics of single particle

    Hello everybody, I have two questions: 1) Is it possible to define a temperature for single particle (or atom or molecule)? If so, how? 2) How to model with quantum Hamiltonian an exchange of energy between a single atom (or molecule) and a reservoir at given temperature ##T## ? Thank you...
  43. S

    Finding the State and Expectation Value for a Free Particle at Time t

    Homework Statement The eigenstates of the momentum operator with eigenvalue k are denoted by |k>, and the state of the system at t = 0 is given by the vector |{ψ}>=\int \frac {dk}{2π} g(k)|{k}> Find the state of the system at t, |ψ(t)>. Compute the expectation value of \hat{P}. Homework...
  44. P

    Many particle physics - Hamiltonian for Fermi system

    Homework Statement Working through problems in Mahan's 'Many Particle Physics' book, and at the end of the 1st chapter there's a question where we're asked to consider a fermion system with three energy states with eigenvalues E1, E2, E3, and matrix elements M12, M23, M13 which connect them and...
  45. F

    B Particle antiparticle collide, teleportation?

    Hi physicists! When a particle and antiparticle collide, (annihilation) as i understand, it in some cases transform and radiate light, which I can buy. But what happen in the teleportation part, where the particle antiparticle pair accurs in an other part in the universe? Do someone have some...
  46. Automata-Theory

    A Particle Moving Along a Ring with Variable Potential

    Homework Statement Alrighty, so here's my problem in a nutshell: Some particle of mass m is confined to move along a ring of radius R. Since it's on a ring, it has periodic boundary conditions--i.e.: For the boundary defined as ##-\pi R \leq x \leq \pi R##, ## x = -\pi R ## and ## x = \pi R...
  47. 1

    Find the potential energy of the particle

    Homework Statement A small bead of mass m is constrained to move on a helix: r (θ) = (R cos(θ), R sin(θ), q θ) where R and q are constants, and θ=θ(t) describes the position of the bead along the helix at time t. The bead is also subjected to a gravitational acceleration g downward (-z...
  48. Titan97

    Normalized equation for particle in a ring

    Homework Statement Normalized equation for particle in a ring, where V=0 on a ring of radius 'a' and infinite everywhere else. Homework EquationsThe Attempt at a Solution Replcing x by rθ, $$-\frac{\hbar^2}{2I}\frac{\partial^2\psi}{\partial\theta^2}=E\psi$$ By guess, I found out that...
  49. M

    Understanding the Importance of Particle Reynolds Number in Fluid Dynamics

    Hello, The particle Reynolds number makes me confused and I hope someone can help me on this please! Normally (as I read in every books and papers) that when a bubble or drop rises in a fluid, the bubble/drop Reynolds number is calculated by: Re = ρUD/μ where U is particle velocity, D can...
  50. K

    Statics of a particle, mechanics, F=ma

    Homework Statement A smooth bead B is threaded on a light inextensible string. The ends of the string are attached to two fixed points A and C on the same horizontal level. The bead is held in equilibrium by horizontal force of magnitude 2N acting parallel to CA. The section of the string make...
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