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. M

    Engineering What can a nuclear engineer do in a particle accelerator ?

    Do they need a nuclear engineer in a Synchrotron ? if yes what kind of job does he do ?
  2. Pushoam

    Particle in a box quantum mechanics

    Homework Statement Homework EquationsThe Attempt at a Solution ## E \propto n^2 ## ## \frac { \Delta E} E = \frac { 2n +1} {n^2} ## In the limit of large quantum number, ## \frac { \Delta E} E = \frac { 2} {n} ##, option (a).
  3. Pushoam

    Force exerted by a particle in a box on the boundary

    Homework Statement Homework EquationsThe Attempt at a Solution The energy eigen - value of a particle in a box is given by ## E_n = \frac { n^2 h^2}{8mL^2} ## . Now, applying classical mechanics , ## \frac { p^2}{2m} = \frac { n^2 h^2}{8mL^2} ## . ## p \propto \frac { 1} L ## , So...
  4. G

    Power given to particle by centripetal forces

    Homework Statement A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration a varies with time t as a = k2rt2, where k is a constant. Show that the power delivered to the particle by the forces acting on it is mk4r2t5/3. [/B] I have solved...
  5. Curtis Cleary

    Find the coordinates of a charged particle given the E field

    Homework Statement The electric field in an xy plane produced by a positively chatged particle is 7.2(4x+3y)N/C at the point (3, 3)cm and 100x N/C at the poiint (2, 0)cm. Note, x and y used here are unit vectors. find the x and y co-ordinate of the charged particle what is the charge of the...
  6. A

    Quick Question on Van de Graaff Particle Accelerators

    Hi everyone. Just a small, quick question I have: Can negative ions be accelerated by a Van de Graaff particle accelerator? My initial reaction is no, because the terminal (the sphere with the charges allocated on the outside) is positive, which means negative ions would be attracted and not...
  7. SameerTahir

    I Source of energy for quantum tunneling of a particle

    If a micro-particle tunnel through a barrier which has higher potential energy than the energy of the particle, then from where does the particle get the energy to cross that barrier?
  8. F

    I How does QFT handle particle creation and conversion?

    I was reading this thread by stevendaryl https://www.physicsforums.com/threads/second-quantization-vs-many-particle-qm.835472/ I have two questions 1. which QFT picture are those, Schrodinger, path integral or Heisenberg. 2.In QM the creation/annihilation operators raise and lower energies...
  9. Gonv

    Probability of finding a particle in a region

    Homework Statement A particle is restrained to move in 1D between two rigid walls localized in ##x=0## and ##x=a##. For ##t=0##, it’s described by: $$\psi(x,0) = \left[\cos^{2}\left(\frac{\pi}{a}x\right)-\cos\left(\frac{\pi}{a}x\right)\right]\sin\left(\frac{\pi}{a}x\right)+B $$ , determine...
  10. T

    Particle in a box question in classical mechaincs

    Hi guys, I am having an issue with what my lecture is saying in these slides, I have attched my slides below. Here is my issue. I am very confused by the ##E<\Delta ## Beacuse I can't see how this has any momentum as it would produce an imagery number. And ye say that ##E<\Delta ## cannot...
  11. M

    A Lorentz-Einstein law of motion for a point particle

    I shall try to expose my question as briefly and clearly as possible. Within a very old and classical approach (Newton), discussions take place in a three-dimensional Euclidean space and the concept of force is represented by a vector which is proportional to the mass of the object at hand (m...
  12. G

    Difficulty with a Point Charge Particle in Electrodynamics

    Point Particle in Relativity and Electrodynamics: “The Classical Theory of Fields” – by Landau and Lifshitz, in its discussion about classical size of a particle, concludes that:- Thus we come to the conclusion that in classical (non-quantum) ‘relativistic mechanics’, we cannot ascribe finite...
  13. ISamson

    B Light, Photons, Waves, Particles: Wave-Particle Duality....

    Me and my friend have recently (half a year ago) had a huge debate, between ourselves, about the wave-particle duality. We took sides in light being a particle or a wave. I was for particle he was for waves. At the end of a hot-filled week of arguing, the debate ended up with the acceptance of...
  14. Souhardya Nandi

    I Can someone explain the Higgs Boson and its significance in particle physics?

    Can anyone shed a bit of light on what a Higgs Boson is, how it was discovered and what its discovery implies for physics ?
  15. G

    Thermal radiation and charged particle acceleration

    A non ionized neutral gas should still emit thermal radiation.,say xenon. Is this solely because of electron transitions ? I ask this because a lot of sources attribute the emission to charge particle acceleration,so neutral atoms should not do this,is this right?
  16. R

    Particle motion + electric field when voltage varies

    Homework Statement Two parallel plates located at a distance "L" from each other they maintain a potential difference "V" because of a battery (as shown in the picture). Through a small hole, made in bottom plate, electrons get into system (with mass "m" and charge "-e"), with velocity "v" and...
  17. Kara386

    Particle track detector to measure the charge of a particle

    Homework Statement The detector is made of two co-planar layers of silicon two metres apart, and there is a plane of wire chambers halfway between them. The wire chamber can measure a track with precision ##100\mu##m. What is the highest momentum a particle can have for which the detector will...
  18. C

    Force between two charged particle beams -- proton and electron beams

    Homework Statement A proton beam is going from north to south and an electron beam is going from south to north, so in which direction is the electron beam deflected Homework EquationsThe Attempt at a Solution . [/B] I thought an electron...
  19. M

    QM: Solving Free Particle with 3D Wave Function Using Fourier Transform

    Homework Statement Hi, i have this problem: In a 3D space, a free particle is described by : $$ \Psi = Ne^{-ar} $$ with $$ r=| \vec r | $$ at the time t=0 . How can we write the wave function whit $$ \hbar \vec k $$ ?Homework EquationsThe Attempt at a Solution I know how to resolve this...
  20. karush

    MHB 243.13.01.18 motion of a particle

    $$\tiny{243.13.01.18}$$ $\textsf{The following equations each describe the motion of a particle.}\\$ $\textsf{For which path is the particle's velocity vector always orthogonal to its acceleration vector?}$ $\begin{align*} \displaystyle (1) r(t)&=t^8i+t^5j\\ (2) r(t)&=\cos(8t)i+\sin(2t)j\\ (3)...
  21. P

    Particle spiraling into the Sun due to "drag" force?

    Hello, Orbital mechanics is a bit of mystery to me. Let us have a particle with mass m orbiting the Sun (with mass M)in a circular orbit with radius R. The velocity vector V is always tangential to the orbit. Let us also have a weak, constant ("drag") force Fd that is always pointing in the...
  22. S

    A Symmetries in particle physics

    We often use SO(N) and SU(N) to describe symmetries in particle physics. I am not clear which one to choose when I try to discuss a symmetry. For example, why do we use SU(3) but not SO(3) to describe the symmetry of the three colors of quarks? Similarly, why do we use SU(2) but not SO(2) to...
  23. P

    Torque acting on a particle in rotational motion

    Homework Statement The following question involves a torque acting on a particle in rotational motion. It provides practice with the various equations for angular velocity, torque etc A particle of mass ##m## initially has position...
  24. Q

    Physics Machine learning with particle physics

    In which fields of physics can we apply machine learning concepts? If I take data science master's with minor in particle physics or astrophysics, what are the possibilities that I would be employed as a physics related data scientist? (I am a programmer and I would like to change my career...
  25. Paul Woods

    I What mechanism enables interaction of the fields?

    In Quantum Field Theory, I am led to believe that there is a different field for each type of particle. When particles interact, it is an exchange of vibration between the fields. What mechanism is at play when one field influences another in this way? It seems I've only ever found...
  26. J

    What is the acceleration normal to PC in polar coordinates?

    Homework Statement Homework EquationsThe Attempt at a Solution Since the force is always directed towards C , angular momentum about C should be conserved . But that doesn't seem to help as we need the relation at any general angle . How should I proceed ?
  27. ISamson

    B Understanding Particle Spins: A Beginner's Guide

    Hello. Could anyone please help me understand particle spins? I read the 'A Brief History of Time' and now would like to understand them better. Basically from zero. Any resources? I have had a look at Wikipedia, but the language is not clear and there is too much information. Thank you.
  28. T

    I Exploring Multi Particle States: Fermions vs. Bosons

    In general, is it of more interest to consider multi particle states consisting of fermions & bosons or multi particle states consisting of only fermions (or only bosons)? I have seen that if it's of the latter type, then the study becomes in certain way more easy to carry on, though the former...
  29. J

    Particle moving down a cone (Newtonian formulation)

    Hi, This a Classical Mechanics problem I've been trying to solve for a few days now. I cannot use Lagrangian or Hamiltonian formulation, it must be solved using classical Newtonian formulation. One must determine the equations of movement of the particle in cartesian, spherical and cylindrical...
  30. F

    I Gravitational field seen be relativistic particle

    The gravitational field of some massive body appears one way to a nearby stationary particle. But does the field appear to be distorted to a particle traveling at relativistic speeds?
  31. RJLiberator

    Expressing expectation values of a particle moving in a periodic potential

    Homework Statement A particle moving in a periodic potential has one-dimensional dynamics according to a Hamiltonian ## \hat H = \hat p_x^2/2m+V_0(1-cos(\hat x))## a) Express ## \frac{d <\hat x>}{dt}## in terms of ##<\hat p_x>##. b) Express ## \frac{d <\hat p_x>}{dt}## in terms of ##<sin(\hat...
  32. bball919

    I want to make a small particle accelerator for cheap.

    I am looking for a way to make a small particle accelerator for really cheap. I am in 8th grade and do not know a lot or have a lot of money but still want a project. if you have a pdf or other doc of plans that would be much appreciated thanks.
  33. A

    Elastic collision heavy particle problem

    Homework Statement Suppose a heavy particle (mass m1) has an elastic head-on collision with a very light particle of mass m2 initially at rest. Show that if m1>>m2, the velocity of the projectile (m1) is practically unchanged, whereas the target particle (m2) acquires a velocity v2' = 2v1...
  34. O

    Lagrangian equations of particle in rotational paraboloid

    Hello. I solve this problem: 1. Homework Statement The particles of mass m moves without friction on the inner wall of the axially symmetric vessel with the equation of the rotational paraboloid: where b>0. a) The particle moves along the circular trajectory at a height of z = z(0)...
  35. J

    Charged particle in a magnetic field

    Homework Statement Homework EquationsThe Attempt at a Solution Velocity of particle at any time t is v = vxi + vyj Net Force on the particle F = (2qvyB)i + (2qvxB)j Net acceleration of the particle = F/m Magnitude of net acceleration = (2qvB)/m Particle has an initial velocity as well...
  36. P

    Fluid Dynamics -- a spherical particle immersed in water

    Homework Statement Consider a spherical particle immersed in water. It will experience random collisions with the surrounding water molecules. Suppose there are such water molecules around the particle. Half (n/2) of the water molecules will push the particle to the right and the other half to...
  37. astrocytosis

    Radial force on charged particle in beam of positive ions

    Homework Statement Many experiments in physics call for a beam of charged particles. The stability and “optics” of charged-particle beams are influenced by the electric and magnetic forces that the individual charged particles in the beam exert on one another. Consider a beam of positively...
  38. D

    Magnetic Force direction on a charged particle moving parallel to a wire

    Homework Statement Homework Equations The right hand curl rule gave me the counterclockwise direction for the magnetic field but I am confused about how is it going to work for the particle. Thanks The Attempt at a Solution
  39. M

    Why do 2 d not decay into alpha particle and neutral pion?

    Homework Statement The reaction dd → απ0 (where α is the Helium-4 nucleus and d denotes the deuteron) has never been observed. Why? Homework EquationsThe Attempt at a Solution [/B] So I checked first the masses to make sure energy/momentum are conserved and found out that mass of 2d is...
  40. M

    Mass of Hydrogen needed to determine lifetime of proton

    Homework Statement The current limit on the proton’s lifetime is determined by observing a large body of water for a long time and noticing that no one of the hydrogen nuclei in H2O have decayed. Assuming that the experiment making this measurement has been going on for 10 years, how many tons...
  41. Rodrigo Schmidt

    Pendulum with a sphere vs with a particle in its end

    So, I'm really bothered with something. Let's suppose there's a simple pendulum with a rigid sphere on it's end. In order to get the motion equations I thought we could use two approaches. One would be using rigid body dynamics (torque, moment of inertia ...), the other one would be using...
  42. Alexanddros81

    The path of the 3.6-kg particle P is an ellipse

    Homework Statement 13.71 The path of the 3.6-kg particle P is an ellipse given by ##R = \frac {R_0} {(1+ecosθ)}##. where R_0 = 0.5m and e=2/3. Assuming that the angular speed of line OP is constant at 20 rad/s, calculate the polar components of the force that acts on the particle when it is at...
  43. Megaton

    Particle Acceleration: Micro Singularities & Future Plans

    Hi please don't butcher me, I'm really not a crackpot...just not sure how to put this or were to post this...on particle acceleration...i have heard of things called micro singularities...are these real could they be used for an alternative energy source...really just curious it seems like...
  44. 6

    Find the path of a particle given a potential function.

    I am tasked with finding the path a particle takes through this potential field. $$U(x,y) = x^2+xy+y^2$$ I then took the gradient, and this produced a pair of differential equations. $$\frac{d^2x}{dt^2}=\frac{1}{m}(-2x-y)$$ $$\frac{d^2x}{dt^2}=\frac{1}{m}(-2y-x)$$ I have yet to encounter set of...
  45. T

    Does changing the spin of a particle in reaction change bond

    I'm looking into chemical battery that use the molecular tension in chemicals like white phosphorus to store heat energy.But finding a way to slow and defuse the heat and flammability of phosphorus with tungsten and sliver is easy. But rebuilding the molecular tension is harder.
  46. C

    Expressing x(t) of a particle (air resistance)

    1. 2D -problem A particle is moving on a frictionless, horizontal surface from ##O_{rigo}## with initial speed ## v_0 ##, as it faces the air resistance force ## F_R ##.2. ## F_R = -mαv ## (where v is a particle velocity) ## \frac {dv}{dt} + αv = 0 ##Show that: ## x(t) = \frac 1 α...
  47. S

    B Learning Gravity: Gravitons nor mass of a particle

    Hi everyone, today, I have a question about quantum gravity, good to begin with. I used Newton's formula to calculate gravity for nêutron , the result exceeded Planck's radius, the question is: could it be that gravity is not necessarily connected to the mass of a particle, nor with graviton...
  48. J

    A Is it possible that a particle is much heavier through a loop correction

    Let's assume, we have standard model singlet particle s that mixes after electroweak symmetry breaking with an exotic, vectorlike neutral lepton N The relevant part of the Lagrangian reads $$ L \supset h^c s N + h s N^c + M N N^c, $$ where h is the standard model higgs and M is a superheavy...
  49. J

    I On the decay of the neutral Sigma particle

    Hello! I wanted to ask why does the neutral Σ decay almost always to one γ(or two) and a neutral Λ. Why can't it decay to anything else? Thanks!
  50. O

    Potential energy of particle in gravitational field of disk

    Homework Statement I have a particle of mass m. The particle is moving in direction of axis z because of the gravitational force of a homogeneous circular disk of mass M and radius a. There is a formula for gravitational force of the disk on the picture. Task: 1) Find the formula of...
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