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.

View More On Wikipedia.org
Recent contents Top users
  1. Salmone

    I Hamiltonian of a particle moving on the surface of a sphere

    In a quantum mechanical exercise, I found the following Hamiltonian: Consider a particle of spin 1 constrained to move on the surface of a sphere of radius R with Hamiltonian ##H=\frac{\omega}{\hbar}L^2##. I knew that the Hamiltonian of a particle bound to move on the surface of a sphere was...
  2. Isopod

    A CDF measures W mass higher than predicted

    The team has found that the particle, known as a W boson, is more massive than the theories predicted. The result has been described as "shocking" by Prof David Tobak, who is the project co-spokesperson. The discovery could lead to the development of a new, more complete theory of how the...
  3. K

    I Particle on a sphere problem in quantum mechanics and its solution

    To solve a particle on a sphere problem in quantum mechanics we get the below equation :##\left[\frac{1}{\sin \theta} \frac{d}{d \theta}\left(\sin \theta \frac{d}{d \theta}\right)-\frac{m^{2}}{\sin ^{2} \theta}\right] \Theta(\theta)=-A \Theta(\theta) ## To solve this differential equation, we...
  4. T

    I Exploring the Universe with a Particle Accelerator

    If experiments were conducted with a particle accelerator in a distant space from Earth or even our galaxy somewhere in the universe would the results change? I.e finding different elements ect..
  5. Jamestein Newton

    Particle Better Textbooks than Griffiths for Particle Physics 101

    Griffiths "introduction to elementary particles" serves a great introduction as a first course on particle physics for undergraduate students. But what are the possible alternatives of this textbook? Like being more beneficial in the long run, more time-consuming, for aspired students. But it...
  6. K

    I Equilibrium equation if the barrier allows particle exchange

    "... two physical systems [seperated by wall], A1 and A2. A1 has ##\Omega_{1}(N1,V1,E1)## possible microstates, and the macrostate of A2 is ##\Omega_{2}(N2,V2,E2)## " "... at any time ##t##, the subsystem ##A_{1}## is equally likely to be in anyone of the ##\Omega_{1}\left(E_{1}\right)##...
  7. G

    Force on a particle of a linear charge distribution

    Hello! I am trying to solve this exercise of the electric field, but it comes out changed sign and I don't know why. Statement: On a straight line of length ##L=60\, \textrm{cm}## a charge ##Q=3,0\, \mu \textrm{C}## is uniformly distributed. Calculate the force this linear distribution makes...
  8. J

    Find net velocity of charged particle in electric field (symbols only)

    We know the net force on the charged particle in the uniform electric field pointing up is mg - qE. To get acceleration, divide the net force by mass to get g - qE/m Plug into kinematic equation and get velocity by itself and substitute$$\sqrt{h(2g - \frac{q \sigma}{\epsilon_o m})}$$
  9. W

    Determine how much energy the alpha particle carries

    I can follow through all of this worked example until the final step 55/56x4.84= 4.75MeV Where does the 56 come from?
  10. K

    I Wavefunction of a free particle has carrier and envelope parts

    If ##\psi(x, t)=\left(\frac{1}{2 \pi \alpha^{2}}\right)^{1 / 4} \frac{1}{\sqrt{\gamma}} e^{i p_{0}\left(x-p_{0} t / 2 m\right) / \hbar} e^{-\left(x-p_{0} t / m\right)^{2} / 4 \alpha^{2} \gamma}##where * ##\gamma=1+\frac{i t} {\tau}##( a complex number) * ##\tau=\frac{m h}{2...
  11. rudransh verma

    How to Calculate Variable Force on a Particle with Varying Coordinates?

    ##W=-k(y\hat i+ x\hat j)d##. I am not getting the coordinate of particle correctly so that I can find the value of d. Also the force is varying.
  12. E

    A The Factorization Theorem in Particle Physics

    I have been tasked with calculating amplitudes of a B meson decaying to a photon and lepton/lepton anti-neutrino pair ,upto one loop and have pretty much never seen this thing before. I will ask my questions along the way as I describe what I am doing. This factorization theorem seems to go thus...
  13. S

    Looking for a book with an Overview of Nuclear and Particle Physics

    Hi, I am doing my PHD in Nuclear/Particle Physics and I am getting all of the information I am using from papers, which are very specific. I feel like I am lacking general knowledge, which is likely to be tested in the defense. Do you know any book where I can get a better overview on Nuclear...
  14. Y

    The velocity of the particle as a function of time

    this is how i try to solve it: can someone please help me with that because i don't know what I am doing worng here.
  15. T

    I Pole mass and non stationary mass of a particle

    Is the pole mass of the particle it's characteristic mass? When particle physicists calculate the mass of elementary particles, like top quark, do they mean the pole mass? If not what makes the apparent mass of a particle different from pole mass?
  16. G

    Length of spin vector for spin-½ particle

    My answer so far in |S| = √3 /2 *hbar but the question states it must be an angular momentum. Is this an angular momentum or am I missing something? Thanks
  17. guyvsdcsniper

    Work per particle of a NaCl chain

    The problem states to find the work per particle to assemble the following NaCl chain. I just want to post my work here to verify I have the correct answer. My work is attached in the image provided.
  18. K

    I Collapse of wavefunction into a forbidden eigenstate for a free particle

    For the free particle in QM, the energy and momentum eigenstates are not physically realizable since they are not square integrable. So in that sense a particle cannot have a definite energy or momentum. What happens during measurement of say momentum or energy ? So we measure some...
  19. B

    B Entangled particle decoherence question

    Suppose there are two entangled particles A and B, separated by a few miles or light years. If the spin for particle A is observed, then from my understanding, A will experience quantum decoherence. And now we can be sure that B will have the opposite spin since B is entangled with A. Assuming...
  20. V

    B What does it mean that a spin 1/2 particle needs two full rotations?

    I know that we can change the spin orientation of a spin 1/2 particle up or down and test it in the Stern Gerlach apparatus. And the spin 1/2 particles need two full rotations to return to the previous state. Questions: 1). what does state mean? 2). Is, Changing spin orientation to up or...
  21. R

    Particle Accelerator concentration

    Summary:: What concentration for electrical engineering works on particle accelerators? What concentration for electrical engineering works on particle accelerators?
  22. K

    I Hamiltonian of a particle in a magnetic field

    I've just started Quantum mechanics by McIntyre and have understood the following about operators which the author wrote till chapter 2: Each observable has an operator Operators act on kets to produce another kets. Only eigenvalues of an operator are possible values of a measurement. Now...
  23. Istiak

    Find force on a particle at time t

    My attempt : ##\frac{\vec Ft^2}{2}=m\vec s## ##s=\frac{Ft^2}{2m}## ##P=\frac{W}{t}## ##k=\frac{\vec F\cdot \vec s}{t}## ##k=\frac{F^2t^2}{2mt}## ##k=\frac{F^2t}{2m}## ##F=\sqrt{\frac{2mk}{t}}## But there was an option which was ##2\sqrt{\frac{mk}{t}}##. And my assumption was that it was...
  24. 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.
  25. penguin46

    How to find integrals of motion for a particle on a surface?

    I have no idea where to even start with this, please help. I barely even know what integral of motion means.
  26. J

    Why isn't the scaling factor included when stating particle mass in eV?

    not technically a homework question, just figured it fit here.
  27. rudransh verma

    Why do we use area under the curve to find displacement in particle motion?

    I calculated v=0 at t=3. s(3) =24 m. s(5)=16 m. So reverse distance that the particle travelled=24-16=8 m. So total distance =24+8=32 m.
  28. alexandrinushka

    B Wave-Particle Duality -- When is it a wave and when is it a particle?

    In order to trigger this "interaction at a point as a particle" does an entity need to meet a certain criteria? Why doesn't any other entity on its way force this transition? Can the properties of this wave be altered? Thank you.
  29. orochi

    Learning about condensed matter physics as a particle physicist

    I am on my first year of my master's degree in nuclear and particle physics, and right now i am ending my first semester, where i decided to take a course in physics of semiconductors. As i end this semester i start to wonder if there was any use in learning about this subject, as it seems like...
  30. duchuy

    Determine the velocity of a particle in mass spectrometry

    Hi, I am trying to determine the velocity of the particle with the mass m coming out of the acclerator. I tried writing : Ep(i) + Ec(i) = Ep(f) + Ec(f) Ec(f) = Ec(i) - Ec(f) But at this step, I'm no longer sure how to express Ep with V because : In my textbook, it's written : Ep = 0,5...
  31. H

    Angular momentum of the particle about point P as a function of time

    I don't understand why my solution is wrong. Here is my solution. $$ r_{\theta} = R\cos{\theta} \vec{i} + R\sin{\theta} \vec{j} $$ $$ v_{\theta} = v\cos(\theta + \frac{\pi}{2}) \vec{i} + v\sin(\theta + \frac{\pi}{2}) \vec{j} $$ $$ p_{\theta} = mvR(-\sin{\theta}) \vec{i} +mvR(\cos{\theta}...
  32. A

    Particle in a changed box

  33. Christian Thom

    A In QFT, what is the momentum of a created particle?

    This seems important to me, since in some interactions, particles are produced by pairs of opposite momentum in the rest frame of the interaction.
  34. M

    I Single particle energy detection

    Hello! If I have a single ion traveling at a given energy (on the order of 10 keV), is there a way to read out its energy in real time with a single pass? Basically I was wondering if there is a device able to measure the current or magnetic field induced by the ion passing through it (while...
  35. M

    The Quantum Uncertainty of a Particle

    Summary:: I'm trying to understand the meaning behind the answer of 2.34... but I haven't taken a quantum class yet so I'm utterly lost. So I took this physics class that's teaching us python and for our final project our teacher assigned random problems to work out, well I got stuck with a...
  36. A

    Trajectory of a charged particle in the magnetic field (variable)

  37. greg_rack

    Conservation of linear momentum, undergrad particle dynamics

    Hi all, I'm opening this thread because of my uncertainty in how to correctly approach this exercise. My first thought was that, since the plate is subject to friction with the floor, it is going to stop, thus the final moment is 0. Hence, from the conservation of linear moment: $$m_Av_A+\sum...
  38. K

    I Classical particle in a Penning trap

    Hello! I have a particle in a Penning trap (moving only along the axial direction) and I have a resonant circuit connected to one of the electrodes, measuring the current induced by the particle. Assume that the energy of the particle is much bigger than the thermal energy of the circuit (##k_B...
  39. Shreya

    What is the relationship between particles and waves in QED?

    "Everything is a particle whose position is predicted by a mathematical wave. Light is not a wave but is packet of energy whose position is predicted by the wave.The same goes for an electron. Interference pattern is a probability distribution of where we are likely to find an electron. When...
  40. M

    Find Final Kinetic Energy of a particle subject to two forces

    I'm having trouble putting the rest of the equations together, I believe I need the different from (0,0,0) to (1,0,0) and then (1,0,0) to (1,1,0) right? Then solve for x direction and y direction. What would I use for Wnc tho? I'm very confused.
  41. rudransh verma

    A particle motion problem in the x-y plane with constant acceleration

    I have attempted but I don’t get anywhere.
  42. Hamiltonian

    I Writing the wave function solutions for a particle in a 2-D box

    The final wave function solutions for a particle trapped in an infinite square well is written as: $$\Psi(x,t) = \Sigma_{n=1}^{\infty} C_n\sqrt{\frac{2}{L_x}}sin(\frac{n\pi}{L_x}x)e^{-\frac{in^2{\pi}^2\hbar t}{2m{L_x}^2}}$$ The square of the coefficient ##C_n## i.e. ##{|C_n|}^2## is...
  43. Rikrik

    B Boundary between a particle in two energy states

    Hi I'm new to quantum mechanics, Looking for some help regarding a concept i am struggling to solve. I am curious if I had a cube of particles in a ground state and another cube with the same particle in a higher energy state. If I placed one upon another, is there anything in quantum mechanics...
  44. A

    I Particle lifetime (half-life) question

    If I have a particle with a average lifetime of 15min, if I take 10 particles confined in a box, after 15 min there will be 5 particles. After 15min 2.5 particles and so on... , but so, at the end there will be the last particle that decades. That particle lived far longer than 15min, but is the...
  45. A

    I Motion of a charged particle -- Changes in KE and PE?

    If a charged particle moves through a potential difference, it gains kinetic energy but does it also lose potential energy? When I accelerate a particle and then I "free it", what happen to its potential energy if the total energy should be conserved?
  46. J

    A Concept of wavefunction and particle within Quantum Field Theory

    -1st: Could someone give me some insight on what a ket-state refers to when dealing with a field? To my understand it tells us the probability amplitude of having each excitation at any spacetime point, but I don't know if this is accurate. Also, we solve the free field equation not for this...
  47. WMDhamnekar

    MHB What are the Kinematics of a Particle?

    I hope the following questions relating to heading of this thread belongs to this forum.
  48. Einstenio

    Motion of a Particle: Solutions & Examples

    This is jut an example to illustrate my doubt. I don't know how to obtain the tracjectory given only the acceleration in this format. I realized that if i can show that there is an constat vector 'a' that satisfy a•r=constant, than the motion would be on the surface of a cone. So i tried to make...
  49. Einstenio

    I Classical Mechanics - Motion of a particle

    Show that a point with acceleration given by: a=c*((dr/dt)×r)/|r|3 where c is a constant, moves on the surface of a cone. This is jut an example to illustrate my doubt. I don't know how to obtain the tracjectory given only the acceleration in this format. I realized that if i can show that...
  50. gromit

    Using Lagrangian to show a particle has a circular orbit

    Hi :) This is a problem from David Tong's Classical Dynamics course, found here: http://www.damtp.cam.ac.uk/user/tong/dynamics.html. In particular it is problem 6ii in the first problem sheet. Firstly we can see the lagrangian is ##L = \frac{1}{2}m(\dot{r}^2+r^2\dot{\theta}^2+\dot{z}^2) -...
Back
Top