Angular momentum Definition and 1000 Threads

Homework Statement I've spent at least 1.5 hours on this problem trying to figure out what i did wrong and I can't find anything. With an exam in two days plus another chapter to go through. Regardless, here are the problem(6) and answer, as well as my work. Hope you can read it, and the...

Homework Statement I have a basic problem where a child jumps tangentially onto the outer edge of a stationary merry-go-round, and you have to use conservation of momentum to find the final angular speed of the merry-go-round. But the next part of the question asks "how much mechanical energy...

I've learned that in a crystal, the crystal momentum is conserved. When one considers the electrons as Bloch waves, they have a momentum that doesn't commute with the Hamiltonian and they have well definite energies, hence they cannot have a well definite momentum, because there is no basis in...

Homework Statement Homework Equations F=ma τ = Iα = rF v=rω, a=rα L = Iω Center of Mass/Moment of intertia equations The Attempt at a Solution [/B] So right now I've tried to model the force acting on the ring as it goes around the peg, but I think centripetal force is involved and I'm not...

Homework Statement If we have a hollow ball completely filled with water which is rolling without slipping on a horizontal ground. If the water freezes which of the parameter will remain unchanged- angular speed, angular momentum, linear momentum, kinetic energy, total energy Homework...

Homework Statement Homework EquationsThe Attempt at a Solution Hi All, My problem is that when I calculate this integral or use software to do it for me I get (3*i*pi)/16, when I've been told that the answer is 1/2i giving a probability of 1/4. Would someone be able to point out where my...

I explained this thinking to a meteorologist once and she couldn't give me an answer. Any physicists want to give it a shot? I find the typical explanation of tornadoes perplexing (that's a polite way of saying I don't believe it). The explanations I've seen claim that tornadoes start out...

Hello all, I have a question regarding the precise definition of angular momentum in orbital motion. I see one definition says angular momentum h, position, r, and radial velocity, r_dot, are related as follows: h = r x r_dot. However, I also see one definition that says h is related to r and...

Homework Statement A 25kg child is spinning on a merry-go-round of mass 150kg and radius 2m at a constant angular velocity of 1rev/s. The child slowly walks to the center of the merry-go-round. Treat the child as a point mass and the merry-go-round as a uniform solid disk, and neglect friction...

Homework Statement Hi I'm having trouble with a question that's asking me to calculate the precession rate for a spinning top. The trouble that I'm having is that I don't understand how the angular momentum points along the axis of the spinning top (picture attached). When I use the formula...

Homework Statement A jumper departs from an inclined plane with a velocity of 100km/h and no rotation. He wants to summersault while he is airborne within 2s.Based on the conservation of angular momentum, he will start tom rotate if his wheel's rotation is slowed down. His wheels are hollow...

There's enough angular momentum in electron spin to get a 1cm radius ring of silver atoms to turn with a period of order days after relaxing from spin-up into randomness. (assuming you could get all of it to show up externally, and not end up in microscopic rotations or l quantum numbers.) I...

HI In a new report published the Thursday 26 October in the journal Science Advances, a team of physicists based in the UK, Germany, New Zealand and Canada describe how new research into "optical angular momentum" (OAM) could overcome current difficulties with using twisted light across open...

I am working through Lessons in Particle Physics by Luis Anchordoqui and Francis Halzen; the link is https://arxiv.org/PS_cache/arxiv/pdf/0906/0906.1271v2.pdf. I am on page 11, equation 1.3.20. The authors have defined an operator ##L_{\mu\nu} = i( x_\mu \partial \nu - x_\nu \partial \mu)##...

Homework Statement A 10 g bullet traveling at 400 m/s strikes a 10 kg , 1.2-m-wide door at the edge opposite the hinge. The bullet embeds itself in the door, causing the door to swing open. What is the angular velocity of the door immediately after impact? Homework Equations p[/B]= mv L = Iω...

Homework Statement A comet orbits the sun. It's position in polar coordinates is given by, $$r(\phi)=\frac{1.8r_0}{1+0.8\cos{\phi}},$$ where ##r_0## is the position at closest approach. Its velocity at this point is given by ##v_0##. Use the concept of angular momentum to find the following...

I read in several places that if, for example, a point particle exhibits uniform circular motion about the z-axis within an osculating plane not equal to the x,y plane, then the angular velocity still points along the z-axis, even though the angular momentum does not (it precesses about the...

Homework Statement The figure shows a uniform thin rigid plank of length 2b which can roll without slipping on top of a rough circular log of radius a. The plank is initially in equilibrium, resting symmetrically on top of the log, when it is slightly disturbed. Find the period of small...

Homework Statement Homework EquationsThe Attempt at a Solution ## \frac { - d \phi }{dt} = V ## V denotes emf. The current is in ## \hat \phi ## direction. Magnetic force is along ## ~\hat s ## direction. Where ## ~\hat s ## is the radially outward direction in cylindrical...

Does a rotating conductor generate an electrical potential due to charges "feeling" a centrifugal force?

Can anyone explain to me why angular momentum of F-19 equals to J=1/2, but if we calculate J with the shell model the result is J=5/2. Thank you

Homework Statement this has been bugging me for a while now the angular momentum about any point p is given as ## \vec {L_p} = \vec {R_{cm,p}} \times \vec {P_{cm}} + L_{cm}\\ ## now if the body precessing around z axis and spinning about its own axis then angular velocity of body in lab...

Homework Statement A system has total angular momentum L about an axis O. Show that the system's angular momentum about a parallel axis O' is given by L'=L-h×p, where p is the system's linear momentum and h is a vector from O to O'. Homework Equations L=r×p or considering a mass element...

Homework Statement Hello, Here is a multiple choice question I would like to be clarified. Suppose that the angular momentum of a system can take the values 0, 1, 2. One carries out a measurement of ##J_z##,the state of the system will: ##a##-Be perfectly known if the result is 0 ##b##-Be...

Hello, Suppose that the angular momentum of a system can take the values 0, 1, 2. One carries out a measurement of ##J_z## on this system. What can be said about the state of the system after the measurement? To what extent can it be perfectly certain if ##J_y## and ##J_x## do not commutate...

One of the reasons I've been so stumped about learning about angular momentum in QM, is that in my classical physics class we only applied it to circular motions. Hence, while I am aware that angular momentum is connected to spherical harmonics, the orbital shapes (besides s) isn't really...

Hello! I have been brushing up my Rigid Body Dynamics. I tried computing the angular speed with respect the Center of Mass (CM) using the usual split of kinetic energy and also the split of Angular momentum using the CM. First, a simple case: Two particles of mass M each separated by a distance...

Hi, me and a friend were discussing calendars and how they go wrong. Apparently one orbit around the sun happens during, on average, 365.242189 rotations around Earth's axis. The persian calendar almost nails it, with a 1 sec per year error, because it is based on star observations rather than...

Homework Statement A single electron atom has the outer electron in a 4f1 excited state. Write down the orbital and spin angular momentum quantum numbers and the associated magnetic quantum numbers for this state. Homework Equations I don't think there is any relevant equations. I think it...

<Moderator's note: Moved from a technical forum and thus no template.> I am trying to design and perform a physics lab. It needs to show the relationship between torque and angular momentum. I have gotten as far designing a 4" PVC coupling and have it on a ramp. I am not sure where to go from here.

Homework Statement A school playground has a carousel, which is simply a circular platform that can rotate around its center axis with negligible friction. This carousel has radius r=1.6 m and rotational inertia I= 177m^2kg. Suppose you are standing beside the carousel which is already spinning...

Homework Statement A hydrogen atom is in the 7f state. What is the magnitude of its orbital angular momentum? Homework Equations L=sqrt(L(L+1)hbar The Attempt at a Solution L= Sqrt(3(3+1)Hbar) 1.41hbar (we want J*S) 1.41*1.054*10^-34 1.47*10^-34J*S

Given a wave function $$\Psi(r,\theta,\phi)=f(r)\sin^2(\theta)(2\cos^2(\phi)-1-2i*\sin(\phi)\cos(\phi))$$ we are trying to find what a measurement of angular momentum of a particle in such wave function would yield. Attempts were made using the integral formula for the Expectation Value over a...

Homework Statement Why is the magnitude of Angular Momentum for an elliptical orbit as such? $$l = mr^2\dot{\phi}$$ where ##\dot{\phi}## represents angular momentum. I have always assumed that angular momentum was $$l = r \times P = mr \times V = mrVsin(\theta) = mr^2\dot{\phi} sin(\theta)$$...

Homework Statement You decide to design a bicycle that will have only 3/4 of the angular momentum of the original wheel when both wheels are traveling along a road at the same velocity. The original wheel had a diameter of d1=37cm and rotational inertia of I1=0.32 m2kg. If your new wheel has a...

https://drive.google.com/file/d/1Z-avhDqYbxDtMzk6Rv_NES7rIvDmzMPz/view?usp=drivesdk 2.conservation of angular momentum 3.for the above question I tried applying conservation of angular momentum about the point of contact where the cyclinders touch each other but my answer does not match with...

A person standing on a stationary friction-less turntable spins a bicycle wheel with the rotation axis of the wheel in the horizontal direction, thus the initial angular momentum is in the horizontal direction (x - axis), say to the right. Now suddenly the person turns the axis of rotation of...

Homework Statement A uniform thin rod of length ##2l## and mass ##m## lies on a horizontal table. A horizontal impulse ##J## is given to the rod at one end. There is no friction. The total kinetic energy of the rod after impulse will be ? Homework Equations ##Jl=I\omega## ##J=mv_{cm}##...

Homework Statement Three small, identical 0.70-kg pucks are attached to identical 0.50-m strings, tied together at a common center as shown in (Figure 1) . Pucks are whirled in circular motion at angular speed 3.0 s-1 What is the magnitude of the angular momentum of the system about the...

Homework Statement In the figure, a 0.400 kg ball is shot directly upward at initial speed 58.3 m/s. What is its angular momentum about P, 1.42 m horizontally from the launch point, when the ball is (a) at maximum height and (b) halfway back to the ground? What is the torque on the ball about P...

Homework Statement A disk with a rotational inertia of 8.38 kg·m2 rotates like a merry-go-round while undergoing a torque given by τ = (5.03 + 1.01t) N · m. At time t = 1.00 s, its angular momentum is 6.57 kg·m2/s. What is its angular momentum at t = 3.00 s? Homework Equations dL/dt= T...

It explains very well many aspects of the Universe. Why should there be any angular momentum though? The idea that the Universe is itself intrisically rotating doesn't make sense.

Why the tangential velocity of a particle increase if there are no external torque acting on it and its angular momentum is conserved? I know that L = I.ω (angular momentum equals moment of inertia times angular velocity) and v = ω.r (tangential velocity equals angular velocity times the...

Lets say I have a massive rod laying on a table with little froction, screwed into the table on one side to become our pivot point, and I lay next to it with my feet pointing towards the rod. First scenario: I position myself very close to the pivot point and push, the rod rotates and I move...

Homework Statement it is given in the image i uploaded Homework Equations L→=r→ × p→[/B] The Attempt at a Solution If the angular momentum of a particle is the cross product of the position vector of the particle from the axis and its linear momentum, how can the angular momentum of m1 and...

There is something I don't quite understand about the law of conservation of angular momentum. Let's say a person is rotating about an axis passing through his/her centre of mass, with an angular speed speed ω1, and has a rotational inertia I1 about about the centre of mass. No torque is acting...

Homework Statement Homework EquationsThe Attempt at a Solution The angular momentum of the upper particle is given as ## \vec L_u = m \vec r \times ( \vec \omega \times \vec r )= m[ \vec \omega r^2 - \vec r ( \vec r . \vec \omega )] = m[ r^2 \vec \omega - \omega r \cos \alpha \vec r ]##...

Recently I was searching the internet and books for the connection between conservation of angular momentum and conservation of rotational energy and found nothing. Let's say an ice skater rotates and draws the arms in - the rotation speeds up. The rotational energy must increase because the...

Homework Statement Homework Equations Angular momentum = moment of inertia * angular velocity Change in angular momentum = impulsive moment v^2=u^2+2as The Attempt at a Solution First I used v^2=u^2+2as to find the velocity of the particle the moment the string goes taut. I got v=\sqrt{8ag}...

Homework Statement A horizontal plywood disk with mass 6.90 kg and diameter 1.14 m pivots on frictionless bearings about a vertical axis through its center. You attach a circular model-railroad track of negligible mass and average diameter 1.04 m to the disk. A 1.40 −kg , battery-driven model...