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. N

    B Do temperature and gravity affect particle or nuclear decay?

    I thought of another question(s) :) does temperature affect the rate of the decay at all? Does temperature effect the energy of the decay; in that the energy of the electron anti neutrino would be higher?
  2. D

    B Can clocks explain the probability of finding a particle in motion?

    New to physics and attempting to get my feet wet reading "The Quantum Universe: Everything That Can Happen Does Happen" by Brian Cox and Jeff Forshaw. Looking to get some clarification on what I hope is a simple concept regarding a particle in motion. The author introduces the use of "clocks"...
  3. S

    What is the world line of a uniformly accelerated particle along the x-axis?

    Homework Statement A particle is moving along the x-axis. It is uniformly accelerated, in the sense that the acceleration measured in its instantaneous rest frame is always g, a constant. Find x and t as a function of the proper time ##\tau## assuming that the particle passes through ##x_0## at...
  4. B

    Does the moon orbit as a classical particle?

    The moon orbits Earth at a radius of 3.84E8 m. To do so as a classical particle, its wavelength should be small. But small relative to what? Being a rough measure of the region where it is confined, the orbit radius is certainly a relevant dimension against which to compare the wavelength...
  5. J

    Conservation Laws and the Movement of Particles around a Pole

    Homework Statement Homework EquationsThe Attempt at a Solution First and foremost I am not sure about how the particle moves around the pole .Can it keep moving in horizontal circle .Or do we have to assume this . Is it something like a conical pendulum ? I don't have much ideas to solve...
  6. P

    Motion of a particle in a magnetic field and viscous medium

    Homework Statement In a homogeneous, non-magnetic, highly insulating and viscous medium, a moving particle experiences a viscous drag given by the law f→=−bv→. Here b is a positive constant. A particle having charge q is projected with an unknown velocity from a point in the medium. It almost...
  7. Andrea Vironda

    I Particle energy and the Lagrangian -- help understanding it please

    Hi, here i see that the energy of a single particle is calculated by deriving the lagrangian to the speed. I obtain something similar to a linear momentum. and then i see that the total energy is this momentum multiplied by speed and then subtracting lagrangian. could you explain to me these things?
  8. P

    Dust in special relativity - conservation of particle number

    Homework Statement My textbook states: Since the number of particles of dust is conserved we also have the conservation equation $$\nabla_\mu (\rho u^\mu)=0$$ Where ##\rho=nm=N/(\mathrm{d}x \cdot \mathrm{d}y \cdot \mathrm{d}z) m## is the mass per infinitesimal volume and ## (u^\mu) ## is...
  9. K

    Particle with mass m and force F(t). Show that x = x(t)

    Homework Statement A particle of mass m is initially at rest at x = 0. It is acted upon by a force F = A cosh (\beta t) (1) A) Show that at very small values of t, the position is approximately given by x(t) = \frac{1}{2}\frac{F_0}{m}t^2 (2), where F_0 is the force at...
  10. grandpa2390

    Determine state of particle: Quantum Mechanics (Phase)

    Homework Statement Homework EquationsThe Attempt at a Solution This is the Solution. I am having trouble understanding parts of it. The first part I don't get is why the e^i... goes with the -z. Did my professor just choose one at random, or is there a specific reason? The second part...
  11. T

    I Spin 1/2 representation of a particle

    A spin 1/2 particle is represented by a spinor while its position is represented by a three-vector. What object should we use to represent such particle if we want to consider both features? That is, what object should we use if we want to consider both spin and space position? It seems there's...
  12. T

    Exploring Trajectories Near a Point: Smooth Curves or Sharp Edges?

    Suppose a particle is moving in an X-Y plane. It's velocity in X direction will be dx/dt and in Y direction will be dy/dt. Suppose at a certain point it's velocity in x direction is zero and in y direction is also zero. Then, dx/dt =0 & dy/dt =0 at that point. Now, what will the trajectory be...
  13. O

    Distance of two moving particles

    Homework Statement There are two particles. There are moving equally on two intersecting lines to intersection. On time t=0 is the distance of two particles d. The velocity of one particle relative to the other has a projection u in the direcion of d. In direction perpendicular to d is the...
  14. K

    Schools Beamline for schools (High school particle physics)

    Hi everyone! I am a high school student and I was wondering if anyone could provide some materials to help a high schooler study modern particle physics. I am interested in participating in the Beamline for Schools competition, which is where a team of high school students submits a proposal for...
  15. T

    I How to study a particle with several features?

    Usually textbooks on QM deals with systems with a single feature. For example, we could analyse electron spin. In such case the state vector is a (function?) only of the corresponding "spin variable" for spin, etc... But suppose I'm interested in say, study about electron spin and also its...
  16. M

    Y coordinate of a charged particle

    Homework Statement On the diagram, a charged particle of charge 0.000003 C and mass 0.000007 kg moves across the electric field 6760 V/m with initial speed 40 m/s. When its x coordinate is 93.3 cm, its y coordinate is (in cm)? Homework Equations y=(e*Em*x^2)/(2*m*v^2), where Em is electric...
  17. Muthumanimaran

    Particle in one-dimensional harmonic oscillator

    Homework Statement This is a question asked in a entrance examination[/B] A charged particle is in the ground state of a one-dimensional harmonic oscillator potential, generated by electrical means. If the power is suddenly switched off, so that the potential disappears, then, according to...
  18. C

    B Particle pair creation probability

    I know that a high frequency light beam is more likely to generate a virtual electron-positron pair than a low frequency one. Can this probability depend on the reference frame? It seems there is a paradox. How do we explain it?
  19. Alexanddros81

    A particle travels along a plane curve (Polar coordinates)

    Homework Statement 13.24 A particle travels along a plane curve. At a certain instant, the polar components of the velocity and acceleration are vR=90mm/s, vθ=60mm/s, aR=-50mm/s2, and aθ=20mm/s2. Determine the component of acceleration that is tangent to the path of the particle at this...
  20. G

    The motion of a particle in the central force

    Homework Statement I just need a hint. So we are given: F = -kr We are asked: Show that: (a) The orbit is an ellipse with the force center at the center of the ellipse. Homework Equations I guess we break it up into its components: The Attempt at a Solution m d2x/dt2 = -kx => x...
  21. yrjosmiel

    Magnetic field of a single charged particle

    Let's say that there's nothing else in this universe except for 2 charged particles: q1 and q2. q1 is moving relative to q2, moving at velocity v. I've read that a magnetic field is made by a moving charge. In this case, the moving charge q1 is moving relative to q2. What would the magnetic...
  22. Alexanddros81

    Particle motion - Path Coordinates

    Homework Statement Pytel Dynamics Problem 13.4 13.4 The particle passespoint O at the speed of 2.4 m/s. Between O and B, the speed changes at the rate of 2.2√v m/s2, where v is the speed in m/s. Determine the magnitude of the acceleration when the particle is (a) just to the left of pont A...
  23. lfdahl

    MHB Particle Motion in a Vertical Plane: Trajectory Equation & Curve

    A particle moves in a vertical plane from rest under the influence of gravity and a force perpendicular to and proportional to its velocity. Obtain the equation of the trajectory, and identify the curve.
  24. D

    Particle traveling towards a plate with an Electric Field

    Homework Statement From a distance of 10 cm, a proton is projected with a speed of ##v = 4.0 × 106 \frac{m}{s}## directly at a large, positively charged plate whose charge density is ##\sigma = 2.0 × 10^{-5} \frac{C}{m^2}##. (See below.) (a) Does the proton reach the plate? (b) If not, how far...
  25. A

    I Constant particle motion due to zero-point energy....

    Hi all, Just a clarification to ask about: if a have an electron (all by its lonesome) in its ground state, it will have non-zero kinetic energy (zero-point energy), even at absolute zero. This should mean the particle (oscillating field excitation in QFT) is always moving. Now, to be clear...
  26. V

    Hamilton - Jacobi method for a particle in a magnetic field

    Homework Statement Hamiltonian of charged particle in magnetic field in 2D is ##H(x,y,p_x,p_y)=\frac{(p_x-ky)^2+(p_y+kx)^2}{2m}## where ##k## and ##m## are constant parameters. For separation of this system use ##S=U(x)+W(y)+kxy+S_t(t)##. Solve Hamilton - Jacobi equation to get ##x(t), y(t)## ...
  27. K

    I Beyond LHC, future particle colliders and lasers

    With LHC currently at 13TEV design energy, and a planned higher luminosity upgrade, is the current plan to double the magnet strength for the current existing LHC to arrive at a 28-33TEV collider, or is it building a completely new future 100 TEV collider near Geneva where LHC is housed but in...
  28. J

    Particle defined "at rest" compared to a magnetic field?

    I am trying to understanding magnetism and I've been running into this thought problem A particle a in a magnetic field B responds with Force F=|q|v x B. frame S: The field is B1, caused by a moving charge/s - current at speed v. the particle is at rest, F=0. frame S' moves with speed v/2...
  29. C

    I Particle at event horizon as black hole evaporates

    If you are observing a particle enter a black hole, you watch its proper time go to zero at the event horizon as it is 'frozen' there from your frame of reference. What happens in your reference frame as the black hole evaporates? While you can't illuminate where the particle is from your frame...
  30. LarryS

    I Conservation laws during particle decay?

    I believe that conservation laws, like for energy and momentum, are obeyed during the particle decay process, e.g. the total energy of the new output particles is equal to the energy of the one input particle. But is that relationship subject to quantum fuzziness? Suppose we, somehow, prepare...
  31. M

    Physics What does an experimental particle physicist do?

    Hi, I'm about to finish my degree on Physics (this will be my last year). I have plans to do a PhD with a professor who works too at the LHCb experiment (CP violation), so I'd research on this topics. But I have doubts on the specifical work of an experimental particle physicist... only analyze...
  32. P

    B Is the electron a particle or field?

    I was having a casual conversation with my uncle the other day and he basically told me that electron is a field. Essentially he claimed that there is an electron field that encompasses the whole universe (like the Higgs field) and what we think of as an "electron particle" is just a fixed point...
  33. Philosophaie

    Physics of a Particle Collision

    I have two point masses, m0 and mp, colliding (with no radii) in an Elastic Collision (no mass loss). One has initial velocity, V0i. The other has initial velocity, Vpi. How do I calculate the initial forces, Foi and Fpi then formulate the final forces, F0f and Fpf yielding the final...
  34. Pushoam

    Work Energy Theorem: particle, system of particles, rigid body

    Question: A) Derive the work - energy theorem for one particle. B) Check whether it is applicable for a system of particles and a rigid bodyWork - energy theorem for one particle system, total sum of work done by individual forces = work done by total force To show the above equality, let's...
  35. J

    Find speed and direction of a particle after collision

    SOLVED THANK YOU
  36. B

    B Magic number 3 in particle physics

    Hi, I found number 3 repeating in particle properties, like: a) 3 generations of matter: electron, muon, tau... b) 3 known charge abs values. (electron/pozitron +/-1, quarks: +/-2/3 and +/-1/3) c) Weindberg angle (~30deg) its 1/3 of right angle. Is there any other 3 hiding in particle...
  37. V

    Energy change for a charged particle

    Homework Statement Without introducing any coordinates or basis vectors, show that, when a charged particle interacts with electric and magnetic fields, its energy changes at a rate $$\frac{dE}{dt}=\vec{v}\cdot \vec{E} $$ Homework Equations ##E_{kin} + E_{pot}= En =## const (1)...
  38. Y

    I Particle calculation during a solar proton event

    Trying to figure out how many particles would bombard an astronaut during a solar proton event. Given that the most possible is around 43,000 particle flux units (pfu) according to NASA. First calculating steradians, assuming a person is 1m^2, 1/(1E9)^2=1E-18. My calculation yields (43000...
  39. C

    Calculate the particle energy in a collision

    Homework Statement The particle J/Ψ can be produced in both proton-proton collisions and electron-positron collisions. a) Consider a proton beam incident upon a fixed hydrogen target. Calculate the energy of the proton beam in the reaction p1 + p2 → p + p + J/Ψ b) Consider two counter...
  40. FallenApple

    I How does measurement work in a two particle universe?

    Say that they are not entangled. Assume classical quantum laws still hold but that there are only two particles in this universe with nothing else. How would one of the particles measure the other? Both particle's location and momentum are nonexistent until a measurement occurs by one on the...
  41. Quantum Velocity

    B Exploring the Dual Nature of Light: Is it a Wave or Particle?

    I heart from my friend that light is both wave and particle but i don't know that is true or not. So can you guy tell me what light actually is? And how light travel from the source and then to our eye?
  42. Erik Ayer

    I Can light be entangled in polarization and still exhibit interference?

    If one beam from SPDC is sent to a double-slit or similar experiment, it can form interference if the which-way information is erased in the other beam. To detect it, photons have to be counted in coincidence because there will be both interference and "anti-interference" that add up to a...
  43. C

    Magnitude of force on charged particle

    Homework Statement Homework EquationsThe Attempt at a Solution I know the equation of force on a moving charge in a magnetic field is F=BqV... Why is the answer A ?
  44. Charles Link

    I Establishing consistency between a wave model of the photon and a particle model

    Note: added to the title should be "and a particle description". ## \\ ## The intensity (energy density) of an electromagnetic wave is proportional to the second power of the electric field amplitude, i.e. intensity ## I=n \, E^2 ##, apart from proportionality constants. Meanwhile the energy...
  45. DoobleD

    I The particle horizon value is ignoring inflation?

    In a paper from 2003, it has been shown that the particle horizon is about 14300 Mpc, or 46.6 billion light years (and it has been recalculated in 2016 with more accurate parameters values at around 14200 Mpc = 46.3 billion ly). From what I understand, the calculation proposed in 2003 takes the...
  46. Sophrosyne

    B Measuring momentum and position in particle colliders

    When we look at those pictures of colliding particles in particle colliders, we see a large collection of curves and lines radiating out from the point of collision, representing the new particles which have been created. So two questions about this: 1) Why are these acting like particles in...
  47. jlmccart03

    Velocity of a particle kicked into four point charge square

    Homework Statement Consider the arrangment of charges (fixed in place) shown in the figure. The square has side length d. (Figure 1) Now suppose the particle with charge q is released. It is "kicked" so that it's initial speed is v. After an unspecified trajectory, it is observed that the...
  48. binbagsss

    QF, action, EoM, mass of particle, on-shell

    Homework Statement Question attached. I am stuck on part d, but give my workings to all parts of the question below. Homework EquationsThe Attempt at a Solution [/B] a) EoM given by E-L equations: Gives ##-\partial_u\partial^u \phi + m^2 \phi - \frac{\lambda \phi^3}{3!} =0 ## b) ## L=T-...
  49. D

    A What Hilbert space for a spinless particle?

    I'm looking for a rigorous mathematical description of the quantum mechanical space state of, for instance, a particle with no internal states. At university we were told that it the Hilbert state of wave functions. They gave us no particular restrictions on these functions, such as continuity...
  50. U

    Particle moving along path, change of angle of inclination

    Homework Statement Homework Equations Equation given in question. The Attempt at a Solution The only thing I could think of was to try changing the y=3x^3 into polar coordinates but I didn't know where to go from there... Could I get some direction to how I should go about this, I'm sort of...
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