Momentum Definition and 1000 Threads

Homework Statement A rod (mass M, length L) is placed vertically on a smooth horizontal surface. Rod is released and after some time velocity of COM is v downwards and at this moment rod makes 60 degrees with horizontal. Find angular momentum of rod about Instantaneous center of rotation...

Homework Statement A circular ring (2m, R) with a small insect of mass m on its periphery, is placed upon smooth horizontal surface (axis of rotation passing through center and perpendicular to the ground i.e disk is lying horizontally) . The insect starts moving with velocity v w.r.t ground...

Homework Statement suppose you're sitting on a rotating stool holding a 2kg mass in each outstretched hand, if you suddenly drop the masses, will your angular velocity increase, decrease or remain the same? Homework Equations dL/dt=net torque when net torque is 0, L=constant=Iw therefore...

Homework Statement Assertion- If linear momentum of particle is constant, then its angular momentum about any axis will also remain constant Reason-Linear momentum remains constant when net force is 0, angular momentum remains constant when net torque is zero which of these statements is/are...

Homework Statement A uniform rod (M, L) is rotated about a point L/3 from its left end. Angular momentum about O Homework Equations 1) L=I(cm)w for purely rotating body 2) L(orbital)= M*v(cm)*perpendicular distance(r) 3) L(spin)= I*w The Attempt at a Solution I got the correct answer in two...

Homework Statement A disk is undergoing pure rolling motion with speed v. The radius of the disk being R and mass M. Then the angular momentum of the disk about the 1)bottom most and 2)top most point Homework Equations 1) L(orbital) = m*v*r where v is the velocity of cm which is...

The process is known as counter-propagating Spontaneous Parametric Down-Conversion (CP-SPDC). In regular SPDC, a photon from a (pump) laser enters a transparent nonlinear crystal at rest, and gets converted into a pair of photons whose total energy and momentum add up to that of the original...

Homework Statement A block of mass m slides down a wedge of mass M and inclination theta from rest. All the surfaces are smooth. Find the speed of the wedge when the speed of the block w.r.t to wedge is v. Homework Equations V(c.m.)=m1v1+m2v2/(m1+m2) The Attempt at a Solution Conserving...

Homework Statement A 7.3-cm-diameter baseball has mass of 150 g and is spinning at 230 rad/s . Treating the baseball as a uniform solid sphere, what is its angular momentum? I'm about to pull my hair out because I feel like I understand everything about this problem perfectly and yet I'm still...

In particle phyisics four-momentum is used and De Broglie relation is used to understand what lenghts can be "seen" in an experiment. Here (page 6) https://people.phys.ethz.ch/~pheno/PPP/PPP2.pdf it is claimed Where ##Q^2## is not actually "momentum" but its the square of the four momentum...

ok so 1- the magnetic momentum is = to u in the k axis ( xyz - ijk ) and the magnetic field B = -A/z4 + Be^Cz) , also in the k axis orientation so the magnetic force F , that is applied on the magnetic momentum is given by 4 choices ; and as i can understnd it, 3 of them are...

Homework Statement Calculate the momentum of a 140 eV photon. Homework Equations p = E/c The Attempt at a Solution [/B] First, convert eV to Joules 140eV (1.60 x10-19J) = 2.24 x10-17J Now for momentum: p = mv p = (E/c2)v p = E/c In my course, however, it says for photons E = hc/ λ...

Homework Statement Four particles of mass 1 Kg each, are moving on a plane with the velocities given in the figure. Homework EquationsThe Attempt at a Solution First I calculated the position of the CoM: Xcm=7/4(i + j) Then I calculated the velocity of the CoM: Vcm= ½i + ¼j For the internal...

I am a hobby reader/listener of pysics, astronomy, special relativity, black holes and more. And a question arose that no amount of YouTube has touched on. Sorry if this is just a stupid question from a hobbist but it truly has me stumped. Or maybe I just have been taught by...

I found that the equation is expressed by there is outer product ...what I really don't get it is if j is a vector then the outer product of j and j is is obtained by multiplying each element of j by the complex conjugate of each element of j which is basically a matrix not a vector

Hello, in classical physics orbital angular momentum is defined as the cross product of the position vector 'r' and the momentum 'p'. A friend told me that all moving objects must have orbital angular momentum (even if it is moving along a straight line). That statement confuses me a lot...

I need to prove that in a vacuum, the energy-momentum tensor is divergenceless, i.e. $$ \partial_{\mu} T^{\mu \nu} = 0$$ where $$ T^{\mu \nu} = \frac{1}{\mu_{0}}\Big[F^{\alpha \mu} F^{\nu}_{\alpha} - \frac{1}{4}\eta^{\mu \nu}F^{\alpha \beta}F_{\alpha \beta}\Big]$$ Here ##F_{\alpha...

From a wiki's vis-viva equation page, it is given that the specific angular momentum h is also equal to the following: h = wr^2 = ab * n How can ab * n be derived to be equal to the angular momentum using elliptical orbit energy/momentum/other equations without having to use calculus or...

If a pulse of light, which has momentum p = E/c, interacts with particles of air, would it not change their momentum over time, causing mechanical energy (sound)? As I understand it, sound is mechanical energy moving through particles as they vibrate. Why can't the momentum of a pulse of light...

I was solving an exercise from Cohen's textbook, but then I got stuck in this question. "Let ψ(x,y,z) = ψ(r) the normalized wave function of a particle. Express in terms of ψ(r) the probability for: b) a measurement of the component Px of the momentum, to yield a result included between p1...

In Special Relativity, we have the four vector, (E/c, px, py, pz). However, isn't the first term just `p` given that `E=pc` for a photon? Why is it an energy-momentum four vector when the first term isn't really energy but momentum?

Homework Statement I have a lambda decaying into a pion and a proton. The lambda is moving with velocity 0.9c and I know the mass of the lambda as well as the pion and proton (these are known constants). I need to find the momentum of the pion and the proton after the decay happens. Homework...

Homework Statement There is a 4 kg mass that has a speed of 6 m/sec on a horizontal frictionless surface. The mass collides head-on and elastically with an identical 4 kg mass initially at rest. The final speed of the first 4 kg mass is: (a) 0 m/s (b) 2 m/s (c) 3 m/s (d) 6 m/s Homework...

Hello Everyone. I Was Wondering how excatly the Gauge invariance of the trace of the Energy-momentum tensor in Yang-Mills theory connects with the trace of an Holonomy. To be precise in what I'm asking: The Yang-Mills Tensor is defined as: $$F_{\mu \nu} (x) = \partial_{\mu} B_{\nu}(x)-...

Homework Statement A particle A (mother particle) with a mass of mA decays to two particles B and C (daughter particles) with mass values of respectively mB and mC. Calculate momentum of the two daughter particles, pB and pC. (at first the mother particle is at rest) Homework Equations The...

Homework Statement A particle with mass m is moving on the x-axis and is described by ## \psi_b = \sqrt{b} \cdot e^{-b |x|}## Find the probability distribution for the particles momentum Homework Equations ## \Phi (p)= \frac{1}{\sqrt{2 \pi}} \int_{-\infty}^\infty \Psi(x,0) \cdot e^{-ipx} dx##...

Homework Statement A point charge q sits at the origin. A magnetic field ##\mathbf{B} (\mathbf{r})=B(x,y)\mathbf{\hat{z}}## fills all of space. The problem asks us to write down an expression for the total electromagnetic field angular momentum ##\bf{L_{EM}}##, in terms of q and the magnetic...

If a ball hits a rod at the top which is pivoted at bottom end then is linear momentum conserved?

It's really confusing if the frictional force IS an external force.. My guess is the frictional force isn't an external force and therefore I can observe the momentum conservation even with friction if I carefully measure the velocity right before and after the collision. But I'm not sure about it..

Homework Statement A long board is free to slide on a sheet of frictionless ice. A skater skates to the board (laid horizontally relative to the skater's motion) and hops onto one end, causing the board to slide an rotate. In this situation, are angular and linear momentum conserved...

Homework Statement How to determine variation of mean momentum of a nucleon with the mass number A of nucleus? Homework Equations R=R_0A^(1/3) The Attempt at a Solution Can't find a solution with elementary approach.

Homework Statement Homework Equations a = v/t p=mv(?) The Attempt at a Solution If an engine is turned on, that means that the ships are accelerating since the engine pushes back on air with a force and air pushes back to propel the ships forward, so I thought (A) would be the answer, even...

In the Dirac equation, the wave-function is broken into four wave-functions in four entries in a column of a matrix. Since there are four separate versions of the wave-function, does each version have the spin angular momentum of h-bar/2? This seems overly simplistic. How does spin angular...

Hi, I found some back of envelop calculations which show that Jupiter accounts for over 60% of the solar system's angular momentum. http://www.zipcon.net/~swhite/docs/astronomy/Angular_Momentum.html Is that correct? A previous thread here on the subject ( now locked for some reason ) claimed...

1. At the instant of the figure, a 6.70 kg particle P has a position vector of magnitude 4.30 m and angle θ1 = 43.0° and a velocity vector of magnitude 3.40 m/s and angle θ2 = 32.0°. Force , of magnitude 7.40 N and angle θ3 = 32.0° acts on P. All three vectors lie in the xy plane. About the...

Homework Statement I am working on the derivation of Kepler's Second Law based on torque and angular momentum. I understand that the vector "L" is equal to the mass (m) times the cross product of the vector "r" and the vector "v." The source I am following then states that L = mrvtheta. I do...

Homework Statement We know the momentum of an electron, which is: 1,48*10^-21. Momentum is m*v (mass*speed) If we divide the momentum by the mass of the electron to find electron's speed, it'll give a value where v> 3*10^8 m/s. Since speed can't be above speed of light, we have to calculate...

Homework Statement the rate of change of the total momentum in a system with respect to time is zero. thus, my textbook says, the total momentum of that system is constant. i'd like to understand how one implies the other if anyone could give me a conceptual explanation? i understand the...

I just want to state that i DID solve the problem. I just seek understanding of it. I'd be really grateful if someone could answer two of my questions at the end of this post. The problem I've solved here is just to show what I'm dealing with. 1. Homework Statement Object 1 is moving towards...

(I hope this post doesn't cross the border into the forbidden realm of quackery and speculation.) I have what seems like a simple question about Special Relativity but I haven’t seen it discussed anywhere, nor has anyone I've asked. Does the nonlinearity of the Lorentz factor provide a way...

Homework Statement [/B] Parts (c) and (f) are the ones I'm having trouble with; Homework EquationsThe Attempt at a Solution [/B] For (c), I assume the problem is meant to involve using the result from part (b), which was H = g(J2 - L2 - S2)/2 . I was trying just to do it by first showing...

Hi guys...i'm not able to understand the rate of change of angular momentum. Suppose i have a disk rotating with an angular velocity vector w along the axis, so the angular momentum is: L=(InertiaTensor)*w, now if i apply a torque the L will change according to...

Homework Statement Homework Equations Li = Lf L = I*omega K = (1/2)*(I)*(omega)^2 The Attempt at a Solution [/B] Given that there are no non-conservative forces in action, I am assuming that the two kinetic energies should be equal. However, as shown by my work above, the two values...

Homework Statement If I want to find the difference in velocities of 2 objects A and B We know the sum of their velocities is A + B But but is the difference B - A Why not A - B? Homework Equations This is from the equation of calculating restitution where (greek letter) = (The difference in...

Homework Statement A cylinder with radius ##R## and height ##h## which has a distributed charge on its surface with density ##\sigma## spins over its axis with angular velocity ##\omega##. If the cylinder has a mass density ##\rho##, find the relationship between magnetic momentum and angular...

Homework Statement Find magnitude of momentum of both blocks Homework Equations p=mv The Attempt at a Solution I am doing my homework right now and just need help understanding finding the total momentum given a before collision/ after collision situation. So i am unsure if i should take the...

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...

1. Homework Statement in picture Homework Equations momentuma+momentumb=momentum of system The Attempt at a Solution So i just spent 1 hour trying to solve this problem and got completely stuck when trying to solve for the angle of ball 2 in the final position i ended up with an equation...

1. Homework Statement In picture above Homework Equations impulse = Δp[/B]The Attempt at a Solution 4.28NS = Δp 4.28NS = pfinal - pinitial 4.28NS + 0.18kg*0.16m/s = pfinal (4.28NS + 0.18kg*0.16m/s)/.18kg = vfinal vfinal = 39.77777778m/s Now i got the direction incorrect but the magnitude...

Homework Statement m = 50kg Distance covered = 100m T = 3.22 Solve for average momentum. Homework Equations X = 1/2 at^2 p = mass*acc*change time The Attempt at a Solution 100 = 1/2 a (3.22)^2 a = 200/10.3684 = 19.28937m/s^2 f = 50 * 19.28937 = 964.4689 change momentum = 964.4689 * 3.22 =...