Particle Definition and 1000 Threads

  1. Ranku

    I Particle Size & Mass: Same Size Different Mass?

    Are there examples of particles with same size but different masses?
  2. ergospherical

    I Calculating Particle Redshift at Time t_0 & t_1

    A question about the FLRW solution has confused a few of us. At time ##t_0## a particle has radial speed ##v_0^r## relative to the fundamental observers, and at a later time ##t_1## it has radial speed ##v_1^r##. The task is to show that\begin{align*} \frac{a_0}{a_1} =\frac{v_1^r \gamma_1}{v_0^r...
  3. S

    B Questions about the position of the particle

    How is it possible for a particle to be in two different states/places at the same instant?
  4. B

    Velocity of a relativistic particle in a uniform magnetic field

    d(ɣmv)/dt = qvB (dɣ/dt)mv + ɣm(dv/dt) = qvB Substituting gamma in and using the chain rule, it ends up simplifying to the following: ɣ^3*m(dv/dt) = qvB Now, I am confused on how to solve for v.
  5. MevsEinstein

    B Particle Function? Particle Equation?

    The following is the wave equation from Electrodynamics: $$\frac{\partial^2 \Psi}{\partial t^2} = c^2\frac{\partial^2 \Psi}{\partial x^2}$$ Where ##\Psi## is the wave function. But because of Heisenberg's Uncertainty, physicists had to come up with another equation (the Schrodinger equation)...
  6. Rafaelmado

    A Energy Levels and Wave Functions of Identical Particle Systems

    a) Find the energy levels of the ground state and the first excited state. b) Find the wave functions (in the coordinate representation) of the ground state and the first excited state. Hints: For a particle of mass m in a harmonic potential of angular frequency ω, the energy of the particle in...
  7. A

    I What are the limits of particle accelerators?

    What prevents making a particle accelerator better than the LHC but only a few centimeters big? After all, you accelerate objects with very small masses. Are there insuperable physical limits? What are the physical limitations?
  8. A

    I What happens to the other particle in an entanglement state?

    if I have two particles in an entangled state, I make them travel in different directions, and I measure the state of only one of them then I know the outcome of the measurement of the other. But when I take a measurement on the first particle, what happens to the second? Does it undergo a...
  9. malawi_glenn

    High Energy (free kindle) Gauge Theories in Particle Physics by Aitchison & Hey

    Free Kindle via Amazon, both part 1 and part 2 Part 1: https://www.amazon.com/dp/B00OD49Z96/?tag=pfamazon01-20 Part 2: https://www.amazon.com/dp/B00OD49Z00/?tag=pfamazon01-20 Enjoy
  10. SkyeAlen

    Kinetic Energy of a Charged Particle near a Charged Ring

    A point charge of value q=8uC is released from rest at a point 1.5m away from the center of the axis of a ring with uniform charge density 3uC/m. The ring has a radius of 10 cm. What is the kinetic energy of this charge when it is 4.5 cm from the center of the charge ring, considering that it is...
  11. LCSphysicist

    Particle in a box that suddenly expands

    My approach was: $$\psi_{2g} = \sqrt{1/L}sin(\frac{n \pi x}{2L}) = \sum c_n \sqrt {\frac{2}{L}} sin(\frac{n \pi x}{L})$$ Summarizing what i have done after that (Fourier series and sum of infinite series), we get the result realizing that, what we want matematically is ##P## $$P =...
  12. Salmone

    I Solving a Particle on the Surface of a Sphere: Obtaining Eigenvalues

    The Hamiltonian of a particle of mass ##m## on the surface of a sphere of radius ##R## is ##H=\frac{L^2}{2mR^2}## where ##L## is the angular momentum operator. I want to solve the TISE ##\hat{H}\psi=E\psi## and in order to do that I rewrite ##L^2## in Schroedinger's representation in spherical...
  13. Adgorn

    Relativistic particle in uniform magnetic field (solution check)

    My solution was as follows: $$\frac {d\overrightarrow p} {dt}=q \frac {\overrightarrow v} {c}\times \overrightarrow B_0$$ The movement is in the ##[yz]## plane so ##|\overrightarrow v\times \overrightarrow B_0|=vB_0##, therefore: $$\biggr |\frac {dp} {dt}\biggr |= \frac {qvB_0} {c}.$$ On the...
  14. K

    The behaviour of an uncharged dielectric particle in a capacitor

    I understand that the particle will be polarised according to its dielectric constant and the electric field across the capacitor. However, since it is similar to an insulator and electrons do not move in and out of the particle easily, the particle will not be charged. How then will...
  15. A

    I Radiate Single Charged Particle: Free Fall in Black Hole?

    Does a single charged particle in free fall into a black hole radiate?
  16. M

    Change in internal energy of particle colliding with piston

  17. ThiagoMNobrega

    I Blender Particle Photon Simulation (interesting results w soft bodies)

    (0:00 / 0:42) photon going light-speed blender simulation I have no idea how a mathematician would translate this example into an equation. Every time I've worked with soft bodies I seem to run short of mathematicians buddies. Regardless of the mathematics of continuous object deformation, this...
  18. A

    I Schwarzschild Metric & Particle Absorption

    The Schwarzschild metric implies a potential different from that of Newtonian gravity. Is there a relationship between it and the process by which particles can be absorbed by other particles? (I haven't studied QFT yet)
  19. Salmone

    I Particle on a cylinder with harmonic oscillator along z-axis

    I need to know if I have solved the following problem well: A spin-less particle of mass m is confined to move on the surface of a cylinder of infinite height with a harmonic potential on the z-axis and Hamiltonian ##H=\frac{p_z^2}{2m}+\frac{L_z^2}{2mR^2}+\frac{1}{2}m\omega^2z^2## and I need to...
  20. W

    I Can you tell the difference between two neutrons in an alpha particle?

    Can you tell the difference between two neutrons in an alpha particle? In one alpha particle, we know that the sum of the spins of two neutrons is zero. Can a neutron with upspin and a neutron with downspin be distinguished from each other? Or can't you tell because it's superimposed?
  21. D

    Why does a free particle in an infinite well have uncertainty bigger than h/2 ?

    So I think I use the right approach and I get uncertainty like this: And it's interval irrelevant(ofc), So what kind of wave function gives us \h_bar / 2 ? I guess a normal curve? if so, why is normal curve could be? if not then what's kind of wave function can reach the lower bound
  22. T

    A A question about charged particle in a magnetic field

    Suppose a molecule from our surrounding air (at ambient temperature) is being selected and is ionized. By some mechanical means, some velocity (say 100 m/s) is added to it and it has been put into a magnetic field perpendicular to its direction of motion. We all know how the molecule will behave...
  23. 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...
  24. 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...
  25. 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...
  26. T

    I Could a Particle Accelerator in Space Reveal Different Physical Laws?

    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..
  27. 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...
  28. 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)##...
  29. 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...
  30. 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$$\sqrt{h(2g - \frac{q \sigma}{\epsilon_o m})}$$
  31. 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?
  32. 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...
  33. 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.
  34. 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...
  35. 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...
  36. 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.
  37. 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?
  38. 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
  39. 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.
  40. 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...
  41. 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...
  42. 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...
  43. R

    Particle Accelerator concentration

    Summary:: What concentration for electrical engineering works on particle accelerators? What concentration for electrical engineering works on particle accelerators?
  44. 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...
  45. 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...
  46. 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.
  47. 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.
  48. J

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

    not technically a homework question, just figured it fit here.
  49. 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.
  50. 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.
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