Particle Definition and 1000 Threads

I am confused whether for electron I have to use rest mass energy (moc2 + 0.8 MeV) or just 0.8 Mev for calculating E. Also how do I find minimum density of a neutron star using above data ? Please help !

Hi guys. Imagine that in the exact instant when a massive particle A crosses the event horizon of a black hole, a Photon does the same,so that they have a race toward the singularity. Who will win the race? Will they have still different velocities?

I need help .I did not A) E < V0 for T =? (passing coefficient ) B) E = V0 for T = ? C ) E > V0 for T =? A

I'm studying particle counters and one of the detection methods uses reflected light to determine the sizes of the particles. What principle does it base on? Thanks!

Hi all, One more virtual particle question (sorry all!): for individuals who would take virtual particles as being 'real' (but unobservable), what is their understanding then of the content of the vacuum? For example, if I place a electron all by itself in the vacuum (thus making it no longer...

r_{13}=r_{23}=\sqrt{(30*10^{-3})^2+(90*10^{-3})^2}=\sqrt{9*10^{-3}}\\ F^E_{13}=F^E_{23}=9E9\cdot\frac{5*10^{-9}\cdot3*10^{-9}}{9*10^{-3}}=1.5*10^{-5}\\ \theta=tan^{-1}(\frac{90*10^{-3}}{30*10^{-3}})=71.565\,degrees\\ \vec{F}^E_{13}=<F^E_{13}cos\theta, F^E_{13}sin\theta> = <4.743*10^{-6}...

I know that a moving particle is subjected to its own field according to Lienard-Wiechert potentials. But is it possible to write a non-relativistic Lagrangian which, upon variation of the action, give rise to the "correct" equation of motion? If such a Lagrangian/Hamiltonian exists, then is it...

Silly question but could someone explain why a real, 'observable' particle is said to be 'off-shell' in an external field? @A. Neumaier 's excellent FAQ notes that the mass shell constraints ceases to have meaning in this case. I'm just not fully clear on why (probably obvious) given that energy...

Hello, When a charged particle is inside a magnetic bottle at the right speed, the particle bounces back and forth and is confined inside the magnetic field. The magnetic force does not work on the particle hence the particle's kinetic energy remains constant. That means that the particle may...

So for the 1D infinite well with the states above, I have ## \psi_{symmetric} = \frac{2}{L} [sin[\frac{\pi x_1}{L}]sin[\frac{2\pi x_2}{L}] + sin[\frac{2\pi x_1}{L}]sin[\frac{\pi x_2}{L}]] ## ## \psi_{antisymmetric} = \frac{2}{L} [sin[\frac{\pi x_1}{L}]sin[\frac{2\pi x_2}{L}] - sin[\frac{2\pi...

Let's say that on the surface of the cladding we have evanescent field due to the total internal reflection between the core and the cladding. The refractive indices of the the core is 1.45 and the refractive index of the cladding is 1.4, and I want to use the gradient force of the evanescent...

This is not a specific homework question, but more of a general query. If provided with a simple vector field indicating forces (for example, an electrical field), can you use integration to determine the path of a particle placed in that field, if also provided with some initial conditions...

Hello, sorry for this stupid question but I am getting confused with equations and I need some help. My problem is the following: I have a dipole with known magnetic field (B=0.234T), it is 110.6 mm long and 89 mm wide (mechanical dimensions). I want to calculate deflection of particles...

So the way I have gone about it is to assume that the equilibrium position is half way between the 2 end points, hence the amplitude of this motion is 9.3/2 = 4.65 cm Therefore the displacement of the particle when it is 2cm away from one end point should be the distance between that point and...

I got the I3 values for the tau(minus) to be -1, as charge is -1 and Y=0. For muon(minus) i got I3 to be -1 too using the same equation and the anti electron neutrino to have an isospin of zero (since Q=0, Y=0). This shows I3 to be conserved (which is needed for strong interaction i believe)...

Maybe because when you don't observe it, the Schrödinger equation predicts the totality of interactions (paths) of the electron over an infinite time, all the paths it can take ( forming a wave like function ) which is actually all the paths the electron can take overlapped... and when u...

I know how to calculate the probability of finding the particle in a region by integrating the mod square of the wave function within that region. But in this question only the operator is provided but not the wave function. I am not sure how am I supposed to proceed with this problem.

So, here's an attempted solution: With ##r_{min}##, $$r_{min} = \frac{1}{B + \frac{\beta}{\alpha^2}}$$ With ##r_{max}##, I get: $$r_{max} = \frac{1}{B - \frac{\beta}{\alpha^2}}$$ or $$r_{max} = \frac{1}{\frac{\beta}{\alpha^2}}$$ Other than this, I and the team have absolutely no idea on how...

Below, I have already solved - I assume - correctly for question 1. Question 2, I am nearing to what I believe is the solution. Question 3, I simply have no idea where I should begin considering that it is interconnected with question 2. With that said, below is the lengthy and somewhat tedious...

Consider a free particle with rest mass ##m## moving along a geodesic in some curved spacetime with metric ##g_{\mu\nu}##: $$S=-m\int d\tau=-m\int\Big(\frac{d\tau}{d\lambda}\Big)d\lambda=\int L\ d\lambda$$...

To begin with, I posted this thread ahead of time simply because I thought it may provide me some insight on how to solve for another problem that I have previously posted here: https://www.physicsforums.com/threads/special-relativity-test-particle-inside-suns-gravitational-field.983171/unread...

I really can't figure out where to even start on this question

Below is an attempted solution based off of another user's work on StackExchange: Source: [https://physics.stackexchange.com/questions/525169/special-relativity-test-particle-inside-the-suns-gravitational-field/525212#525212] To begin with, I will be using the following equation mentioned in...

Right, so I thought I'd done this correctly but clearly not because my velocity is greater than the speed of light, where have I gone wrong? P = (M, 0, 0, 0) p1 = (E1, p1x, p1y, p1z) p2 = (E2, p2x, p2y, p2z) P = p1 + p2 p2 = P - p1 square each side to get (p2)2 = P2 - 2Pp1 + p12 therefore (m2)2...

I calculated the potential energy of the particle as follows : But I am not sure how to calculate the kinetic energy. I know that if it was a satellite orbiting a Earth, I could use ##\frac {GMm} {r^2} = \frac {mv^2} {r}## to calculate the velocity v and they I could calculate kinetic energy...

ok I chose e for the zeros

I've been looking hard (really, I have) for an explanation of what 'spin' is. Is there any way to explain this in a physical-real way, or is it 'just a thing'? Every description I have come across, and I mean dozens, say something like 'well, it's like angular momentum but it isn't really that...

I want to focus this question on understanding the force ##F(r)## I get (thus, I want to focus on c) ). However, below the dashed line, I included steps on how I derived ##F(r)##. We are going to work in polar coordinates. Knowing that the acceleration is: $$a = \Big( \ddot r - r \dot...

A tachyon or tachyonic particle is a hypothetical particle that always travels faster than light. Most physicists believe that faster-than-light particles cannot exist because they are not consistent with the known laws of physics. - Tachyon definition The photon is a type of elementary...

Two identical point-sized particles with the same Y-coordinate were traveling along the X and Z axes respectively. Given that gravity is acting parallel to the Y-axis, will the particles when they eventually collide, continue traveling along the same linear path due to work done by either being 0?

A particle moves along the x-axis. The velocity of the particle at time t is $6t - t^2$. What is the total distance traveled by the particle from time $t = 0$ to $t = 3$ ok we are given $v(t)$ so we do not have to derive it from a(t) since the initial $t=0$ we just plug in the $t=3$ into $v(t)$...

Would it be practical to accelerate a 50 picogram particle to speeds on the order of 1,000,000 meters per second (in a high vacuum environment) using methods typically used in particle accelerators? 2 methods that come to mind are a series arrangement of parallel pate accelerators and a moving...

I tried solving the differential equation by integrating both sides wrt t but this does not work out and I am doing something wrong. How do I integrate such an equation properly? d²x/dt² = -k²/x³ => dx/dt = -k²t/x³ => x = -k²t²/2x³ + d

For instance, in the case of a simple pendulum, it is quite acceptable to write down ##-mg\sin{\theta} = ma_{tangential}##, and go from there. However, if we introduce a rotating body which is not a particle, we may still calculate its torque from its centre of mass, however we can no longer...

I've found two methods for doing this problem and they give different answers. Method 1: Assume the larger nucleus does not move, and simply equate energies before the collision and at the point of closest approach:$$\frac{1}{2} m v^{2} = \frac{qQ}{4\pi\epsilon_{0}r}$$ Method 2: Assume the...

So I am making the assumption that the resulting particle Z is emitted at rest. For part a I believe that since the two positron beams are symmetric they would each provide half of the energy to create the Z particle so the KE of each positron would be 91.187GeV/2, I am ignoring the rest energy...

So I know that the total energy of the system initially is 775.5MeV, because the meson is at rest. Also by conservation of energy I know that the total final energy of the system is the same thing. I also know that the initial momentum of the system is 0 because the particle is at rest. This...

Attempt: I'm sure I know how to do this the long way using the definition of stationary states(##\psi_n(x)=\sqrt{\frac {2} {a}} ~~ sin(\frac {n\pi x} {a})## and ##\int_0^{{a/2}} {\frac {2} {a}}(1/5)\left[~ \left(2sin(\frac {\pi x} {a})+i~ sin(\frac {3\pi x} {a})\right)\left( 2sin(\frac {\pi x}...

I have insertet the equations for H and P in the relation for the commutator which gives $$[H,P] = [\sum_{n=1}^N \frac{p_n^2}{2m_n} +\frac{1}{2}\sum_{n,n'}^N V(|x_n-x_n'|),\sum_{n=1}^N p_n] \\ = [\sum_{n=1}^N \frac{p_n^2}{2m_n},\sum_{n=1}^N p_n]+\frac{1}{2}[\sum_{n,n'}^N...

Homework Statement:: A particle with mass m is effected by potential V(x) = ∞ when x<0, -V0 when 0<x<a, 0 when x>a A) Set up a relation from which the energy for bounded states can de determined B) For which values V0 does the particle have only one bounded state? Homework Equations...

Hi! I'm studying Shankar's Principle of quantum mechanics I didn't get the last conclusion, can someone help me understand it, please. Where did the l over rho come from?

Once I have read that we can’t know a actual position of a particle because to see the particle we need to send photons and when we send photons it colides with the particle and change it’s position. Is this true?

I need help with part d of this problem. I believe I completed the rest correctly, but am including them for context (a)Show that the hermitian conjugate of the hermitian conjugate of any operator ##\hat A## is itself, i.e. ##(\hat A^\dagger)^\dagger## (b)Consider an arbitrary operator ##\hat...

What I've seen of the experiment involves sending a stream of particles through the slits. I'm extrapolating when I say that the interference pattern could be caused by electromagnetic fields (in the case of massive particles), especially because the particles are moving and probably spinning as...

Firstly, since there is no condition for the z axis in the definition of the potential can I assume that V(x,y,z) = .5mw^2z^2 when 0<x<a, 0<y<a AND -inf<z<inf? If so then drawing the potential I can see that the particle is trapped within a box with infinite height (if z is the...

Hi, Can anyone please help me with the following: I have found the velocity of projection, no problem, it is v = 2*sqrt(10) Also, in obtaining this value, I have also found the extension in the string when in equilibrium, it is x = 2 Now on to the time of flight. The given answer is: t =...

For this problem, since the weight force on the "particle" (child) is not always aligned with the tangential circular path of the disks, I couldn't think of a way to use rotational kinematics equations. As such, I tried to solve the problem using work principles (namely, that the change in...

ok again I used an image since there are macros and image I know this is a very common problem in calculus but think most still stumble over it inserted the graph of v(t) and v'(t) and think for v'(t) when the graph is below the x-axis that participle is moving to the left the integral has a...

In quantum mechanics, the Eigenfunction resulting from the Hamiltonian of a free particle in 1D system is $$ \phi = \frac{e^{ikx} }{\sqrt{2\pi} } $$ We know that a function $$ f(x) $$ belongs to Hilbert space if it satisfies $$ \int_{-\infty}^{+\infty} |f(x)|^2 dx < \infty $$ But since the...

I don't really know where to start as this is not exactly my homework and I finished school some 15 years ago. I looked into my old high school notes, the last time I ever had anything about mechanical waves and sound. Unfortunately, we never learned anything about sound waves causing...