Momentum Definition and 1000 Threads

In classical field theory, translational (in space and time) symmetry leads the derivation of the energy-momentum tensor using Noether's theorem. From this it is possible to derive four conserved charges. The first turns out to be the Hamiltonian, and thus we have energy conservation. The...

Homework Statement So basically I have a train with two joined carriages which become separated (m1) Mass one =13563kg and (m2) Mass two =30394kg. the initial velocity of the joined carriages is 5.00m/s (u1). When the carriages separate I have the final velocity of (m2) which is 0.96m/s (v2)...

Hi. I have come across the following statement - the eigenvalue equation for J+ is given by J+ | j m > = ħ √{(j+1)-m(m+1)} | j , m+1> My question is this - how can this be an eigenvalue equaton as the ket | j, m> has changed to | j , m+1> ? Surely the raising/lowering operators don't have...

Please bare with me as I'm a beginner with this stuff, and am just learning lol But I was wondering if I did the right math to figure out the momentum of the Space Shuttle. Linear Momentum, in classical mechanics, is the product of the mass (the measure of an objects resistance to acceleration...

Why is it that introducing a hard cut-off ##p^{2}=\Lambda^{2}## breaks Lorentz invariance? Is it simply that it introduces an energy scale and energy is not a Lorentz invariant quantity? Sorry if this is a trivial question, but I just want to make sure I understand the reasoning as I've...

I have been wondering, simple question, really: What is the relationship between momentum and centripetal acceleration, if there is one? Is there a relationship in terms of velocity, maybe, or is there none whatsoever?

Homework Statement So me and my friend were comparing our homework and we noticed that although we had the same answers, we both had different ways of answer them. So I was just wondering who's work, my friend or mine, is the most correct?Here's the questions. 1. Calculate the momentum of a...

Homework Statement Playing in the street, a child accidentally tosses a ball (mass m) with a speed of v=23 m/s toward the front of a car (mass M) that is moving directly toward him with a speed of V=20 m/s . Treat this collision as a 1-dimensional elastic collision. After the collision, the...

Homework Statement A 500g putty ball moving horizontally at 6m/s collides with and sticks to a block lying on a friction-less horizontal surface. If 25% of the kinetic energy is lost, what is the mass of the block? Homework Equations initial (i) = final (f) m1v1+m2v2 = m1v1+m2v2...

According to WKB approximation, the wave function \psi (x) \propto \frac{1}{\sqrt{p(x)}} This implies that the probability of finding a particle in between x and x+dx is inversely proportional to the momentum of the particle in the given potential. According to the book, R. Shankar, this is...

So I did this lab on momentum on jets and the theory is that "a force is applied on the plate due to change of momentum" the jet both impacted on a flat plate and on a hemispherical plate; now i understand that the greater the angle of deflection of the water jet, the greater the change of...

Homework Statement A spaceship of frontal area 25 m2 passes through a cloud of interstellar dust at a speed of 1.0x106 m/s. The density of dust is 2.0x10-18 kg/m3. If all the particles of dust that impact on the spaceship stick to it, find the average decelerating force that the impact of the...

I've been doing some research into Einstein's equation E2=(mc2)2 +(pc)2 but apart from in nuclear reactions, where you can use the simpler E=mc2 as momentum=0, I have been unable to find any applications. Thank you in advance

Note: Please only give hints please! No answers because I want the satisfaction of solving it. 1. Homework Statement A mass M at height h above flat round and falling vertically with velocity v breaks up explosively into 2 parts. The kinetic energy given to the system in the explosion is E...

When an RF antenna absorbs a signal, the momentum is transferred in quantized photon-electron interactions. The electrons in the metal will be given both perpendicular momentum (the actual signal information) and momentum in the direction of propagation (shown below): The momentum in the...

Homework Statement A photon with the length of lambda hits a cathode perpendicularly to its surface. As a result, an electron leaves its surface perpendicularly to the direction of the photon. How much momentum was transferred from the photon to the cathode? The work function of the cathode is...

Does a rotating magnetic field possesses angular momentum in the direction of rotation? I suppose this comes down to a broad question about the physical nature of fields in general. I love the Einstein-de Haas effect, where an iron core spins in the opposite direction of the induced spin...

Hi. To show that [ L2 , L+ ] uses the following commutators [ L2 , Lx ] = 0 and [ L2 , Ly ] = 0 . But if [ L2 , Lx ] = 0 this shows that L2 and Lx have simultaneous eigenstates ; but then should L2 and Ly not commute ? Thanks

Homework Statement How much work is required to accelerate a proton from rest up to a speed of 0.999c? What would be the momentum of this proton? Homework Equations p=γmv The Attempt at a Solution I got part A, which was the momentum. I found that to be 20.1 GeV. Now for part B I have to find...

I rarely hear about momentum entanglement, do you know any experiments/applications for momentum entanglement? If we do momentum entanglement on 2 particles, and then we accelerate one of the particles, will the other particle slow down to obey conservation of momentum? or entanglement will be...

When analyzing the conservation of angular momentum of a particular system, should we use the same p.o.r. before and after or can we use different p.o.r.'s? As far as I know, we should always use the same reference, but sometimes I see several solutions that use different references in my...

I need websites or books that has quantum mechanical exercises in particular that finds the total angular momentum eigenvalues (for example two spin 1/2 systems). Do you know where I can train?

A paradigm shift for me occurred when, I now realize, that position and momentum are random variables in QM. As such, it does not make any sense to say things like "take the derivative of the position with respect time". Instead QM has the position and momentum operators which operate on the...

Homework Statement A block of mass 200g is suspended through a vertical spring. The spring is stretched by 1.0 cm when the block is in equilibrium. A particle of mass 120g is dropped on the block from a height of 45 cm. The particle sticks to the block after the impact. Find the maximum...

Homework Statement If the Earth, with a radius of 6400 km, were collapsed into a sphere of the same mass, having a radius of 10 km, what would be its rotational period? Homework Equations L = Iw The Attempt at a Solution I can solve this if the moment of inertia is given but since it isn't I...

Hi there, I've been trying to solve the following problem, which I found looks pretty basic, but actually got me really confused about the definition of angular momentum. Problem The trajectory of a point mass m is described by the following equations, in spherical coordinates: r(t) = r_0 +...

Hello, A dude I'm discussing momentum and kinetic energy with says this: "Place two masses in deep space, the only gravitational attraction is from each other. One of the masses is ten kilograms and the other is one kilogram. From Newton's Third Law we know that the mutual attraction is equal...

How did this definition come to Newton's mind? Force seems to be the effort we apply. So, qualitatively, more the effort, more the force. How to understand intuitively that this formula given by Newton gives a quantitative measure of Force? And, how do we know that Force does not depend on more...

Homework Statement Homework Equations K.E = p^2/m The Attempt at a Solution [/B]

Light has no mass. It has a momentum, though. That means it can potentially push things when reflected and therefore lose energy due to the doppler effect, right? Does it mean that it gains energy when it slows down things and doesn't lose any energy if it doesn't push anything? If the whole...

A car traveling north makes a right turn, to head east. How do the tires completely offset py and simultaneously create px? (If the tires merely acted like guidance jets, it might turn to face east but continue traveling north.

Hello Physics Forums, I have a fluid dynamics problem which appears to challenge some momentum principles. Suppose you have two submarines (like below), identical in shape, but not in mass. One of the submarines has density equal to the fluid, while the other is denser. They move at the same...

This is something I do not know how to explain. Although velocity decreases due to friction with ambient air, momentum should be conserved and, therefore, it entrains mass. What is the reason that momentum should be conserved?

Homework Statement A door ( a rod of length ##L##, mass ##M##) rotates with angular velocity ##\omega## about a point ## H ##, and approaches a stop at ##S##. ##H## and ##S## are along the same line, and separated by a distance ## s ##. Show that the angular momentum of the door about the point...

Homework Statement If the steel disk has mass of 200 kg and a radius of 2 meters you can make it spin by applying a force to the rim. This torque increases the angular momentum of the disk. Suppose the force is 20 Newtons. How long would you have to apply it to get the wheel spinning 5...

Does the momentum always get transferred from lower velocity to higher velocity(may be along a negative velocity gradient.) Consider the collision between 2 bodies M1 and M2,(M1<M2) but both having the same momentum.So M1 will have a higher velocity than M2(V1>V2). Now if the velocities V1 and...

Homework Statement Prove that if a particle starts in a momentum eigenstate it will remain forever in a eigenstate given the potential c*y where c is a constant and y is a spatial variable. Homework Equations (h/i)d/dx is the momentum operator and a momentum eigenstate when put in the...

I have two balls spinning with v1, omega1 and v2, omega2. They collide elastically with no tangential slip, resulting in new values for v1, omega1 and v2, omega2. I have the two components v1 & v2 figured out in the plane of contact, where angular momentum does not come into play. But I am still...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color] My question is from an exam in analytic mechanics. The question was about an object sliding on inclined plane, the plane's angle is constant, and the plane is free to move along X axis...

Is the wavefront velocity if an OAM mode 1 light beam proportional to its wavelength? I understand that the helical structure step length gives the wavelength of the beam. In this case, a small wavelength beam would travel much slower. The problem is, f=v/λ, but now v<c and if λ is shorter then...

I'm trtying to get a better understanding of the spatial part of the energy-momentum tensor, and although similar questions have been asked here, I think the point I do not fully grasp has not been covered so far. The stress tensor can be considered as "momentum flux density" tensor. If I...

Homework Statement Spacecraft, with vacuum inside, in free-fall, contains a small mass captured against a fully-compressed compression spring against one wall of the craft. Release the spring and mass. Mass is accelerated by recovering spring (elastic potential energy turning to kinetic)...

Homework Statement A bullet of mass 0.011 kg is fired at a speed of 850 m/s. It embeds itself in a man of mass 90 kg. a) Find the momentum of the bullet before it strikes the man. b) Assuming it takes 0.1 seconds for the bullet to come to rest after hitting the man, calculate the average...

Good afternoon! I would like to preface by saying, yes, this is for a project. I am only posting here to see if my method of solving is correct before I finish the project incorrectly. Homework Statement I chose two balls, mass A: .553 kg and mass B: .410 kg I recorded their collision and...

It is known that particles with rest mass cannot travel at the speed of light. Can we also say that particles that travel at subliminal velocity, like these OAM photons do, have mass? It has been demonstrated [1] that these beams can be thought as made of photons that posses intrinsic OAM, and...

Homework Statement Homework EquationsThe Attempt at a Solution I'm not sure how to go about working on this. What I have tried is this line of reasoning: 1x4He needs 2x3He. 2x3He needs 2x(2H + p) Energy released is therefore 12.98 + 2(5.51) _+ 2(0.41) = 24.82 MeV. However, it does seem...

Homework Statement A punter drops a ball from rest vertically 1 meter down onto his foot. The ball leaves the foot with a speed of 18m/s at an angle of 55##^{\circ}## above the horizontal. What is the impulse delivered by the foot (magnitude and direction)?[/B]Homework Equations...

Homework Statement Homework Equations Momentum conservation and Energy conservation equations The Attempt at a Solution Ok First I translated the units, ##1000 \frac {kg} {min}=16.66\frac {kg} {s}## ##10\frac {km}...

I was watching a lecture and there was a connection drawn between classical rotational energy and quantum rotational excitation. The energy of a rotating system is $$E = (L^2) / 2 I $$ with L being the angular momentum and I the moment of Inertia. Then to make it quantum$$ n^2 * ħ^2$$ was...

Homework Statement I was recently assigned a project of, tl;dr, building a wall to reduce the maximum force during a collision. Let me start by describing the setup as best as I can. First, here's an image: These aren't the exact track and carts we're using, but they provide a great...