Particle Definition and 1000 Threads

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. J

    A particle slides down a non-fixed hemisphere

  2. Vanadium 50

    B Trouble at Fermilab

    Adrian Cho, who is always excellent, has a very good article on the recent difficulties Fermilab has been having: https://www.science.org/content/article/trouble-and-strife-deepen-famed-u-s-particle-physics-lab A little background. In 2007, the current contractor received the DOE contract to...
  3. M

    Uncertainty in particle position

    For this problem, My solution is However, the my answer for ##\Delta x## is not correct. The correct answer is ##\Delta x = 0.18a##. Does someone please know what I have done wrong? Kind wishes
  4. M

    What would a gluon computer be like?

    So I was always wondering what a gluon computer (a computer using gluons instead of electrons or photons for the computing medium) would be like. There is absolutely NO literature anywhere online for it and the only mention is a brief card (with no description) in a sci-fi board game. People...
  5. PotatoMan

    B Gluons turning into quarks and antiquarks

    When looking into how particles decay, it seems that it will happen if there exists an interaction between the initial and final state, and if the final state has lower potential energy than the initial. (i.e. turning mass into kinetic energy) If this is true, how does a gluon turn into a quark...
  6. S

    I Only one type of elementary electric charge?

    Is there only one type of elementary charge? The type of elemental charge that appears on particles such as electron, proton, etc. It is well known. Could there be another different type that we don't know yet?
  7. M

    A "The 7 Strangest Coincidences in the Laws of Nature" (S. Hossenfelder)

    I appreciate Sabine Hossenfelder's latest video, and thought I would assemble some references. There's a mix of particle physics and cosmology topics. In general, the coincidences mentioned are mainstream topics in cosmology, whereas the particle physics coincidences are not. 1) Proton/electron...
  8. Turnernater

    I Where are these neutrino masses coming from?

    Ever since High school I've seen this model of the "particle zoo," including in my recently finished particle physics undergrad course, and I can't seem to find where the mass numbers for the neutrino family is coming from! Sure the model has a less than sign, but from what I understand all...
  9. seonjunyoo

    B I wonder about a particle's energy when mass is obtained or lost

    According to Einstein's formula, energy is generated when mass is obtained or lost. What does losing or gaining mass mean for an atom or particle valence? It's simply because of the formula I don't want this kind of answer I want. What does it mean for an atom or particle to lose or gain mass...
  10. S

    B Electron's movement after getting hit by a photon that bounces at 90 degrees

    I just started studying Quantum physics and i'm learning about Comptonspreading and I have this question in my book that I don't completely understand So if an electron is standing still, then it gets hit by a photon moving in a straight line into the electron. The photon then bounces off the...
  11. chwala

    Find the value of ##T## and distance of particle in the first ##4## seconds

    solution is here; I just need to understand this part ##14.7 = -14.7 =9.8T##... why initial velocity upwards is a negative value? or i am interpreting it wrongly. ........... In my reasoning, ##v=u+at## ##0=14.7 + (-9.8)t## ## t_1=1.5## in reverse direction, from top to start point ##T##...
  12. Bling Fizikst

    Particle projected from above a dome

    Since the ball will follow a parabolic trajectory , i threw it into the coordinate plane with particle starting from the origin . $$y= kx^2$$ Differentiating wrt ##t## : $$ gt=2ku^2 t\implies u=\sqrt{\frac{g}{2k}}$$ where $$k=\frac{\sin\theta}{R\cos^2\theta}$$ Now , final speed when it reached...
  13. Sturm

    I Why Can a W Boson Decay into Quarks of Different Generations?

    Hi, i was wondering why a W Boson must always decay into a quark anti quark pair of the same generation. Why can it not for example decay into an up ant anti strange pair?
  14. hello478

    Wave movement and particle movement

    A wave pulse moves along a stretched rope in the direction shown. Which diagram shows the variation with time t of the displacement s of the particle P in the rope? A B C D my answer was c because i thought that the particle would move in the same way the wave was coming...
  15. Hennessy

    Help Calculating probability between 2 limits for the ground state

    TL;DR Summary: Looking for help on a Intro to QM Problem Hi All, THIS IS A GRADED PIECE OF WORK AT MY UNIVERSITY PLEASE DO NOT JUST GIVE ME THE ANSWER , I have made this post to see if what i've calculated seems reasonable, it sounds unlikely as 0.4 - 0.5L is in the middle of the well. The...
  16. D

    B What kind of energy is needed to create particles such as quarks and electrons?

    Quarks and electrons have clear electric polarity. So, can we assume that an electric source as electromagnetic is needed to create those kinds of particles?
  17. keyzan

    Probability of finding a particle in the right half of a rectangular potential well

    Hi guys it's me again. I need help with this exercise which reads: a particle of mass m, placed in an infinite rectangular one-dimensional potential well that confines it in the segment between ##x = -\frac{a}{2} and x=\frac{a}{2}##, is at instant ##t=0## in the state: ##|\psi \rangle =...
  18. amandela

    Instantaneous Acceleration Given Equation for Velocity

    This is from an old exam. The velocity of a particle moving along a straight line is v = 4 + 0.5 t. What is the instantaneous acceleration at t=2? The solution is supposedly 2 because a = dv/dt = t. But I thought dv/dt here would be 0.5. What am I missing? Thanks.
  19. keyzan

    Wave function of infinite potential well

    Hi guys i have this exercise: A particle of mass m, confined in the segment -a/2 < x < a/2 by a one-dimensional infinite potential well, is in a state represented by the wave function: 1. Determine the constant N from the normalization condition. To do this, I have to integral the square...
  20. R

    Final speed of particle far away from rings with opposite charges

    When I submitted it, this answer was incorrect.
  21. K

    I Why does wave amplitude indicate particle location in QM?

    Why do we say that wave amplitude tells us where we are likely to find the particle versus where we are likely to find the wave from the particle? Isn't the later a more accurate description of the QM math?
  22. imgamedeving

    I How often would a ϕ meson decay to a electron-positron pair?

    I know the mass of J/ψ to be 3097 mev and the mass of phi to be 1018 mev. I know that J/ψ decays to electron and positron 5% of the time. I also know the full width of j/psi to be 0.092mev and that the phi meson lives 50 times longer than J/ψ . My professor claims that if I am given that info...
  23. L

    Plotting the trajectory of a particle in polar coordinates

    Hi, Unfortunately, I am not quite sure whether I have solved/plotted the following task correctly I started by resolving the expression ##\phi=2 \pi t## to t so that I can represent ##\rho(t)## with ##\rho(\phi)## The vector ##\vec{e}_r## was written in my lecture as follows...
  24. A

    Find the linear speed of the particle when system rotates about axis

    Question image: The question should be solved by conservation of mechanical energy.( I assume surface density##\sigma## and acceleration due to gravity##g=const.##)Therefore: $$PE_i+KE_i=PE_f+KE_f$$ The axis of rotation ##PQ## is line of zero potential. Then 1) ##PE_i=\int Fdy## Since...
  25. S

    How to convert to the number of sand and Nylon particles from mass

    I calculate 4.8x10(^10) particles /kg of sand in the sample. Do you find the same ? Is my solution correct ? How many particles do you find ? Thanks in advance !
  26. Hill

    I Relativistic Lagrangian of a particle in EM field

    I'm following the derivation in Lancaster and Blundell. First, the Lagrangian for the free particle is ##L=-\frac {mc^2} {\gamma}## and the action ##S=\int -\frac {mc^2} {\gamma} \, dt##. Then, EM is "turned on" with the potential energy ##-qA_{\mu}dx^{\mu}##. Then, they say, the action becomes...
  27. F

    Particle experiencing only an angular force, determine the r dot

    Hey, I've been working on this for a couple hours, and still no luck. Since the force in the radial direction is zero, I set r'' = rθ'^2. Then since Fθ = m r' θ' and, since it's in polar coordinates, Fθ = m(2r'θ' + rθ''). Setting these two equal, I get: -r'θ' = rθ'' At this point, I'm...
  28. G

    Particle moving from one potential to another

    Attaching the image of the problem as an image. Somehow text is not copied from the book. Somehow, I can't imagine the picture in my head. We can do it in 2D plane. I know, it mentions the solution, but need to see the drawing, otherwise, my logic fails. I thought that maybe, first half space...
  29. Slimy0233

    Calculate Distance Traveled: Instantaneous vs. Average Velocity

    edit: I don't know why my latex isn't rendering, any help would be appreciated. Edit 2: The question was due to a misunderstanding I had, I thought integrating instantaneous velocity would give me average velocity. I have attached what I have tried so far. I had a doubt. Can you calculate the...
  30. L

    Particle on a ring (components in the postion basis)

    Hi, I have problems with the task part b and g To solve the task, we have received the following information Task b First, I wrote down what the state ##\psi## looks like $$\psi=\frac{1}{\sqrt{N}} \sum\limits_{k}^{} \psi_k$$ $$\psi=\frac{1}{\sqrt{N}} \sum\limits_{k}^{} \frac{1}{\sqrt{N}}...
  31. M

    Why Define Internal Energy Using Average Mechanical Energy?

    For this, They say internal energy is the sum of the all the mechanical energies of each particle in within the thermodynamic system, however, they then define internal energy differently using the average mechanical energy for all particles within the system (Pink equation). Does someone...
  32. E

    Thermodynamic equilibrium for systems only open to particle exchange

    I am only interested in the initial equilibrium conditions, and I am struggling to convince myself whether that should correspond to the equality of chemical potentials for H2 or an equality of temperatures as well. My work is as below: We take both gases as simple ideal (this is only relevant...
  33. 4

    I Spin operator and spin quantum number give different values, why?

    Assume spin 1/2 particle So the spin operator gives +/- hbar/2 eg. S |n+> = +/- hbar/2 |n+> But S= s(s+1) hbar = sqrt(3)/2 hbar So I'm off by a factor of sqrt(3). I suspect I am missing something fundamental about my understanding of spin. My apologies and thanks in advance.
  34. ahmadphy

    I The effect of a field on a particle depends on the particle velocity?

    Assume there is a force (vector field) on the space .....does the effect of this field on the particle(the change of momentum) at some position depend on the speed at that position? And is it related to the time interval dt the particle experiences this force ? Can i say dt=dx/v? And is that...
  35. S

    Direction of movement and sign of the charged particle

    From the picture, the particle experiences upwards force. But how to determine the direction of motion? I think there are two possibilities: if the particle is positive, it moves from Q to P and if it is negative it moves from P to Q. Thanks
  36. M

    Why Did I Get a Different Average Velocity Calculation for the Particle?

    For this, The solution to (a)(i) is 0 ft/s. However I got -4 ft/s. The formula I used was, ##v_{avg} = \frac{s_f - s_i}{t_f - t_i}## ##v_{avg} = \frac{\frac{1}{2}t^2_f - 6t_f + 23 - \frac{1}{2}t^2_i - 6t_i + 23}{t_f - t_i}## ##v_{avg} = \frac{ \frac{1}{2}(t^2_f - t^2_i) - 6(t_f - t_i)}{t_f -...
  37. A

    Help debugging MCNP code - particle lost and zero latice element found

    I keep getting particle lost error even though there were no hole in the lattice. Can someone identify any mistake in my code?
  38. H

    I Where is the mass of a particle located?

    in https://www.physicsforums.com/threads/black-holes-to-explode-due-to-evaporation.1051054/page-2#post-6869765 there was a discussion about where the mass inside a black hole is located. according to general relativity it is located in an infinite small point, which causes spacetime to be...
  39. Y

    Quantum Theory, particle in a ring

    hello i would to get some help with my homework. 1. true 2. i dont know 3. true 4. i dont know 5, false 6. i dont know about 2,4,6 i really have know idea what to think I really appreciate help
  40. monsterhart

    1D Particle & Energy w/ F(x): Am I doing this right?

    A) I just did what it said to do: $$\sin\left(4x_{1}\right)=1\implies x_{1}=\frac{\arcsin\left(1\right)}{4}\ m=\frac{\pi}{8}\ m\approx 0.392699081699\ m$$ B) I modified the method from an example from the lecture the other week: $$U\left(x\right)=-\int...
  41. snoopies622

    B How to show that particle spin includes angular momentum?

    I understand how a massive, electrically charged spinning ball would have both angular momentum and a magnetic dipole, and i can see how the Stern–Gerlach experiment shows that the magnetic dipole of an electron is quantized. What kind of experiment demonstrates a connection between electron...
  42. DomDominate

    B What exactly is spin? Does the standard model work without spin?

    I did some research online and found that "When certain elementary particles move through a magnetic field, they are deflected in a manner that suggests they have the properties of little magnets." To explain this phenomenon, physicists invented the concept of spin. So far so good. What I...
  43. H

    Why a particle with spin=0 can't posses a magnetic dipole moment?

    Hi, I would like to know why a particle with spin=0 can't posses a magnetic dipole moment? Using Wigner-Eckart theorem for ##\langle j,1,m,0|j,m \rangle## I get ##\langle j'|| \vec{J}|| j \rangle = \hbar \sqrt{j(j+1)} \delta_{jj'}## It seems like the right hand side is the magnetic dipole...
  44. S

    B Magnetic Field & Particle Spin: Does It Matter?

    Does the magnetic field caused by moving particles depend on the particle spin value? Eg a stream of say protons spin 1/2 is creating a magnetic field. If the particles are (say) lithium nuclei spin 3/2 instead, does that create the same strength field ? (same conditions of course)
  45. 1

    MCNP6.2 - Source particle started in a cell of zero importance

    Hi everyone, My plan is defining a surface source on a cylindrical object (cylindrical surface+top end+bottom end) and I am interested in what happens outside the cylindrical body. To avoid distortions of particles starting on the surface, directed inwards and emerging on the other side of the...
  46. Q

    A particle in an infinite square well

    What I am lost about is b, rather the rest of B. I am not sure what it means by probability density and a stationary state.
  47. E

    A Symmetries of particle interacting with external fields (Ballentine)

    I am following along with Ballentine's (in his *Quantum Mechanics: A Modern Development*) construction/identification of symmetry generators as operators representing the standard observables (observables here being used in the sense of a physical concept which have operators representing them)...
  48. Z

    I Free particle probability distribution

    Abstract: If a laser shoots photons at a pinhole with a screen behind it, we get a circular non-interference pattern on the screen. Is this distribution Guassian, and if not, what would its wave function be? ===================== Assume a double-slit like experiment, but instead of double...
  49. haziq

    How Can I Solve for the Travel Time of a Particle in a Potential?

    I’ve been trying to solve this for ages. Would really appreciate some hints. Thanks
  50. flamebane

    Electric Flux through a semi-spherical bowl from a charged particle

    I believe this does has a couple of Calculus aspects to it but I don't really know how I'd find the surface area of inside the bowl. The answer sheet says the answer is 252 with a margin of error of +/- 1
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