Angular momentum Definition and 1000 Threads

I'm learning about beta decay and as I understand in beta decay we get: neutron → proton + electron And since all these have spin 1/2 we have that the conservation of angular momentum is not conserved. The neutrino with spin 1/2 is proposed to also exist in the process to solve this so that...

Homework Statement At the instant illustrated, which best describes the angular momentum of the ball and net torque on the ball, as measured around the origin? L⃗ is in the kˆ direction, ⃗τ is 0. Homework Equations torque= (F)x(r) Tension in rope= (mv^2/r)+qvbThe Attempt at a Solution I am...

suppose a platform "P" is rotating about the z-axis wrt x-axis . another platform "Q" rotating about z-axis below "P" with same angular velocity wrt x-axis standing on Q , P is at rest wrt Q, After some time rotational inertia of P about z-axis starts changing with time standing on Q , P will...

Homework Statement A 60.0 kg woman stands at the western rim of a horizontal turntable having a moment of inertia of 500 and radius 0f 2.00 m. Turntable is initially at rest and is free to rotate around frictionless vertical axle through its center. Woman then starts walking around the rim at...

Hello, I have a question about using the properties of conservation of angular momentum to provide mechanical resistance. Basically, I'd like to create a device that spins a disk similar to a gyroscope. The device has an external input that, depending on the configured orientation of the disk...

Homework Statement Show that ##<L_x^2> = <L_y^2>## using the commutation relations. The system is in the eigenstate |l,m> of ##L^2## and ##L_z##. Homework Equations ##[L_x, L_y] = i \hbar L_z## ##[L_y, L_z] = i \hbar L_x## ##[L_z, L_x] = i \hbar L_y## ##[L_x, L^2] = 0## ##[L_y, L^2] = 0##...

Homework Statement Initially collar is at rest with theta = 0. Find \dot\theta=f(\theta). And find maximum theta reached. Homework Equations I don't know if i allowed to use angular momentum about top-right frame corner as it's accelerating. But i definitely will need second Newton law:)...

Hello, I've been doing some research on gravitational waves since their discovery, and I found that all of the places I looked were missing an important piece of information, that is: What is the mechanism by which angular momentum is being conserved. All of places that I've searched will...

Two free electrons approach each other, so they start to emit photons due to bremsstrahlung. Where does the angular momentum carried away by the emitted photons come from?

Recently I've been studying Angular Momentum in Quantum Mechanics and I have a doubt about the eigenstates of orbital angular momentum in the position representation and the relation to the spherical harmonics. First of all, we consider the angular momentum operators L^2 and L_z. We know that...

Two things I'd like to discuss: 1. The conservation of angular momentum. If you have two discs rotating on the same fixed rigid axis, will these nullify each other? I.e. Create no net angular momentum? 2. How / is it possible to convert angular momentum to linear momentum in the sense to be...

Hey, I am new to the forum, and would certainly appreciate help in understanding spin - although I realize that perhaps no one really understands spin. If a beam of spin polarized electrons are absorbed in a target, then the target will start to rotate. This kind of makes sense on a...

Good morning all, Recently in a modern physics course of mine, my professor was covering the topic of energy levels and ionization energies and it included a diagram very similar to this one: While it is interesting to learn that these diagrams correspond to a very specific and strict set...

Let's say a train powered by electric third rail drives around without friction on a circular track, and light is shining out of the train windows, said light carries angular momentum, like light emitted from rotating or revolving things tend to do. Where does that angular momentum come from...

Homework Statement A block of mass m slides down a frictionless ramp from height h above the floor. At the base of the ramp it collides and sticks to the lower end of a uniform rod, length L, mass 2m, that is suspended about a pivot at point O, about which it is free to rotate. Express...

Homework Statement Two objects with mass of m are connected with a rod with length 2l and with no mass. The center of the rod is pinned so that it can spin. Object with mass M comes with speed v and sticks to m. There is no friction. 1) What is the angular speed w after collision? 2) FInd the...

Homework Statement Question - Models of global warming predict that large sections of the polar ice caps will melt. Explain what effect this will have on the rotation of the Earth, however slight. Homework Equations L = Iw The Attempt at a Solution Assuming polar ice caps protrude the earth...

If there is no net torque acting on a system total angular momentum of the system will be conserved as well as angular momentum of each body present in the system will be conserved. And if there are two bodies /two charges present as a system and one of them (let's say body 1 )produces torque...

Homework Statement I am trying to show that as the alpha particle is being scattered, the angular momentum magnitude at point M is m r^2 \frac{d \phi}{dt}. Diagram: Homework Equations Linear Momentum: ##\vec L = \vec r \times \vec p ## Repulsive Coulomb Force: ##\vec F = \frac{k 2Ze^2}{r^2}...

Putting spin on the ball improves it’s stability (the spin imparts angular momentum and it takes an outside torque to change angular momentum), but at a cost. As you know, for a given input of energy, spin consumes some of that energy and leaves less for translation. Part A: So, How much more...

Homework Statement There are two problems: (A) Consider two identical billiard balls (spheres), each of mass M and radius R. One is stationary (ball 2) and the other rolls on a horizontal surface without slipping, with a horizontal speed v (ball 1). Assume that all the frictional forces are...

Homework Statement : [/B] A vector is perpendicular to B vector, and they stay still, relative to the body. No torque is applied on the asteroid, although he dissipates very little rotational kinetic energy, due to drag on dust clouds. It was also determined that the asteroid is a long body...

Homework Statement Attached Homework Equations ##J_+|j,m⟩ = ћ\sqrt{j(j+1)-m(m+1)} |j,m+1⟩## ##J_-|j,m⟩ = ћ\sqrt{j(j+1)-m(m-1)} |j,m-1⟩## ##J_z|j,m⟩ = mћ |j,m⟩## ##J^2|j,m⟩ = ћ^2j(j+1) |j,m⟩## The Attempt at a Solution Hi there, For part a, the expression we're looking for is given, but...

Homework Statement Is angular momentum of a projectile in projectile motion conserved ?[/B]Homework EquationsThe Attempt at a Solution Gravitional force vector is acting along direction of displacement vector. Thus external torque is 0. Thus angular momentum is conserved throughout projectile...

If we were living in a two dimensional world. would we know about angular momentum of an object?

Homework Statement Is it possible for the respective angular momenta of each individual particle in a system to be zero, but the system's collective angular momentum be nonzero? For example, a puck on a frictionless air table moves (without spinning) toward a point on a rod that is not the...

When a nucleus gamma decays, the gamma has its intrinsic spin of ##1\hbar##, but it can also carry away a significant amount of angular momentum in addition to that. Quadrupole radiation is very common, and in exceptional cases you can even get gammas with 5 or ##10\hbar##. Now suppose I do the...

I've been working on my SR book http://www.lightandmatter.com/sr/ and its presentation of a suite of related mathematical tools such as the Levi-Civita tensor. This is aimed at the upper-division undergraduate level, although there are optional sections at the end of some of the chapters that go...

Homework Statement https://scontent-sea1-1.xx.fbcdn.net/hphotos-xft1/v/t35.0-12/12414351_10206719685063143_386848762_o.jpg?oh=16c004481b7417fad921c37acc4942be&oe=56793416 Homework Equations Angular momentum: H= Iw Parallel axis theorem: Io = I + Md^2 Moment of Inertia of thin plate about it's...

Hi, Two questions. 1) I'm having trouble understanding the stability of the stable Lagrangian points (L_4 and L_5); Wikipedia explains that if an object in the L_4 or L_5 of a planet is pushed closer towards the common center of gravity of the Sun and the planet, the increased speed that comes...

Homework Statement A rod that is fixed to a vertical wall is attached through the middle of a solid disk. A piece of the disk crumbles off when the disk is spinning and rises vertically. The system is the chip and the spinning disk. Assume no friction. A. How does the direction of the angular...

Dear guys, Recently, i am confused with a problem in my textbook of mechanics. The question is, suppose there is a disk, placed horizontally, rotate about its center with angular velocity ω. A ball move with respect to the center of the disk in a trace of Archimedean spiral r=αθ. The angular...

Homework Statement 2. The attempt at a solution I set the initial angular momentum of the disk = to the sum of : rod's angular momentum, angular momentum of disk, rod's center of gravity and disk's center of gravity. With the reference point being at B. Why is the velocity of the rod's...

Homework Statement A device consists of eight balls each of mass 0.6kg attached to the ends of low-mass spokes of length 2.1m, so that the radius of rotation of the balls is 1.05m. The device is mounted in the vertical plane. The axle is held up by supports that are not shown, and the wheel is...

I would like to prove that the angular momentum operators ##\vec{J} = \vec{x} \times \vec{p} = \vec{x} \times (-i\vec{\nabla})## can be used to obtain the commutation relations ##[J_{i},J_{j}]=i\epsilon_{ijk}J_{k}##. Something's gone wrong with my proof below. Can you point out the mistake...

Homework Statement [/B]Homework Equations L = I ω L= r x p The Attempt at a Solution For b) My proffesor found the moment of inertia at the point at which the wheel touches the ground, and used the formula L = I ω What I don't understand is why can't one use L= r x p to solve the...

Homework Statement Indiana Jones standoff. Person A fires a 20g bullet at 500 m/s at Person B, who is holding a sword. The bullet sticks to the sword. The angular momentum of the sword is 2.225 kgm^2 / s. The moment of inertia about the center of mass of the sword is .7082 kgm^2. The...

Homework Statement A metal bar of length r is attached to a pivot point at (0,0) in the XY plane. A steel ball is projected toward the free end of the rod and strikes it at the tip. Show how to calculate the angular acceleration of the bar after the collision and draw a vector diagram to scale...

I know that the angular momentum is conserved in the below example, but intuitively I am struggling. Anyway, here goes! Homework Statement A bullet that is traveling without spinning hits and sticks into a filled disk tilted on its side an arbitrary distance "d" away from the center of mass...

Homework Statement A 2.0-m measuring stick of mass 0.175 kg is resting on a table. A mass of 0.500 kg is attached to the stick at a distance of 74.0 cm from the center. Both the stick and the table surface are frictionless. The stick rotates with an angular speed of 5.30 rad/s. (a) If the...

Homework Statement A particle of mass m moves under the influence of a central force F(r)=-mk[(3/r^2)-2a/r^3]rhat Show that if the particle is moving in a circular orbit of radius a, then its angular momentum is L=mh=m√(ka) Homework Equations L=mvr for circular orbit The Attempt at a...

Starting with the orbital angular momentum of the ith element of mass, $ \vec{L}_I = \vec{r}_I \times \vec{p}_I = m_i \vec{r}_i \times \left( \omega \times \vec{r}_i\right) $, derive the inertia matrix such that $\vec{L} =I\omega, |\vec{L} \rangle = I |\vec{\omega} \rangle $ I used a X b X c...

Homework Statement Consider two forces F and -F that act at different points on an extended object. Show that the net force of this combination is zero and that the torque about any point P is independent of the location of P, and depends only on the separation of the two points at which the...

I've been a fan of this forum for a while, but never signed up for it, today I'm stuck on this problem and can't find anywhere other than Chegg but I don't have a premium account. 1. Homework Statement A meter stick is at rest on frictionless surface. A hockey puck is going towards the 30cm...

Homework Statement A thin ring of radius r is constrained to rotate with constant angular velocity ω as shown in attached picture. Let the linear mass density of the ring be ρ(θ)=ρ0(2+sin2θ) where ρ0 is constant. a) Find the angular momentum L of the ring about O, at the instant the ring is in...

Homework Statement What is the best way to evaluate the rotation of a angular momentum eigenket (## | l,m \rangle ##) around an Cartesian axis? 2. The attempt at a solution I've tried to use the method in...

Angular momentum is conserved in a closed system. Is thermal isolation required too? An example special case in mind is a closed cavity high speed rotation. It contains high pressure gas and the thermal flow is driving convection currents creating turbulence and or a heat pumping loop...

In an electron system (spin =1/2, l = 1) the total angular momentum will be J=S+L

Ok, so as far as I understand it, it is impossible to turn linear momentum (p) into rotational momentum (L), but I don't quite understand why. The main thought experiment I have in my head is this: A ball in space is traveling with a momentum mbVb, and gravity and friction are assumed to be...

[Moderator's note: thread spun off from a previous one on a related but different topic.] Well that's another question that has been puzzling me for quite some time and would love to know the answer to it... Imagine 4 tubes of equal length, making a square, with 4 identical photons running...