Momentum Definition and 1000 Threads

I am struggling to find correct approximation for the problem. Is momentum conserved at the immediate impact of... (1) Can I ignore gravitational force and potential for the spring which is connected to ground and vertically upholding a mass . ( using equilibrium)

Hi. If I drop an inelastic body, its potential energy first gets converted to kinetic, then to deformation energy. We use conservation of energy without taking into account the kinetic energy gain of the earth during the fall. However, at first sight conservation of momentum seems to be...

There appears to be a conservation of charge momentum (qv) analogous to that for mass (mv) although in the case of charge it is more potential in nature. A change in the flow of charge (or current) produces changing magnetic and electrics fields according to Maxwell's equations. These in...

Hello and thank you for welcoming me to your forum! To get started, I would like to give you a little help: In the pattern experiment, when firing the cannon, if part of the momentum reaches the bird, and if another part of the momentum manages to stun the fish, what part of the momentum would...

Do the contractions affect physics in any frame? Examples: If length contraction reduces mass in the direction of motion, and therefore reduces the total momentum. (from observer's perspective) If in the reference frame of a station, the moving train weighs less than it did when parked...

So i started off breaking up the problem into two sequences, right before the collision and after the collision has happened. I need to find the first ball's speed immediately before the collision which is no problem. PEi = KEf > mghi = (1/2)mvf (vf being the velocity right before the collision...

Solved equation 1 for v1f and then substituted into equation 2 and solved for v2f. Got 2.22 as the answer, but it said the answer is incorrect.

The momentum of the robot is 95.0 x 1.4 m/s towards the platform. This must be equal and opposite to the momentum imparted to the beam. Dividing 133 kg m/s by 330.0 Kg gives a velocity of 0.403 m/s for the beam. So the relative velocity of the robot relative to the platform is 1.40 - 0.403 =...

Hi, I was reading the interesting lecture of Feynman about Characteristics of Force -- https://www.feynmanlectures.caltech.edu/I_12.html He basically says that nominal definitions like mathematical definitions of "abstract" objects have actually no physical meaning. For instance take the...

Now if I'm given a ##\phi(k)##, and I'm asked to find ##\langle p \rangle##, ##\langle p^2 \rangle##, etc. Am I justified to say that ##\langle p \rangle = \hbar \langle k \rangle## and that ##\langle p^2 \rangle = \hbar^2 \langle k^2 \rangle## ?

Before the engine is switched off: $$P_{Initial rocket} = (m_{i}c, 0)$$ $$P_{photons} = (E/c, -p_{photons})$$ where E is the energy of the photons and ##p_{photons}## is the 3 momentum of the photons. Rocket after engine switched off: $$P_{Final rocket} = (m_{f}c, m_{f}v)$$ By conservation of...

Given that the ions are initially at rest my initial velocity is 0. Therefore my Vavg is equal to vf/2 Using the formula Vavg = Change in positon/time, I can solve vf to be equal to 2r/t. Using the momentum principle, I get an equation of 2r/t = FnetT/12m -> Given that the mass of the ion is...

For question 1. I am stuck. I know that the equation involves time and possibly rate, should solve for distance. But not sure how to set it up with information given. 2. Ft= m 🔺️ v F(3)= (100kg)(30m/s) 3 s= 3000 kg m/s Same applied to question 3. 3. F(2)= (100kg)(-30m/s) F(2) = -3000 kg m/s...

800 - (32 x 9.8) = 32v/0.18 where v = velocity this gives me v = 2.736 m/s The answer given, however, is 800 = 32v/0.18, i.e. v = 4.5 m/s The difference, of course, is the weight of the child. I don't understand why this is not allowed for in the net force acting on the child. Can someone put me...

I tried searching on the internet for hours to find an answer, but I didn't find any.

I'm looking into center of mass and I saw the derivation of: ## V = \frac{\sum\limits_{i = 1}^{n} m_iv_i}{\sum\limits_{i = 1}^{n} m_i} ## I understand how it's derived, so no need to explain this further. It's a velocity of the frame in which total momentum of our objects is zero. Forget...

For this problem, The reason why I am not sure whether it is a valid assumption whether momentum is conserved because during the collision if we consider the two masses to be the system, then there will be a uniform gravitational field acting on both masses, and a spring force that is acting...

From the bus driver's point of view, who is at rest, the ball's initial velocity is ##u+v##. After the collision, its velocity has to have the same value, but an opposite direction, so ##-(u+v)##. So that means that relative to me standing on the ground at rest, the ball's new velocity is...

Here is question + drawing.

I understand that conservation of motion comes from the action and reaction pairs of newton's third law. When it is triggered, two forces appear that cancel when analyzed as a system. My question is how is it that momentum is conserved if before the shot there was no force in the system and...

In the lab, how accurately can we measure momentum? What is the max value of the uncertainty in position as the uncertainty in momentum approaches zero? Or vice versa. What experiments do these types of measurements?

Hello, simplified the Angular momentum problem that comes up when i try to solve a mass moving inward or outwards and it does not conserver the angular momentum properly. I have tried this is many software by now, or by someone else and we all have found that there is no angular momentum...

The homework statement isn't exactly as is mentioned above. The actual problem statement is as follows: This is problem 3.8 from John R. Taylor's Classical Mechanics; however, my question is not related to the main problem itself but one particular aspect of it. Now, in the same textbook (John...

I just don't understand should I take u relative to the plane or relative to the ground. I tried to solve it like this: $$p_{final}=m_{0}v-m(u-v)-M(u-v)$$ $$p_{initial}=m_{0}v$$ $$\Delta p=-m(u-v)-M(u-v)$$ ##m_0## is mass of the plane. $$F=\Delta p$$ $$F=-m(u-v)-M(u-v)=(m+M)(v-u)$$...

How did the d(mv)/dt become the other two? Can someone explain how do we derive for new formulas in physics?

For this, Does someone please know how do we derive equation 9.9 from 9.8? Do we take the limits as t approach's zero for both sides? Why not take limit as momentum goes to zero? Many thanks!

How should I calculate the angular momentum carried by a current carrying circular wire? Is it correct to consider the angular momentum of the electrons moving with drift velocity? Like ##L = n m_e v_{drift} r## where ##r## is radius of the loop, and ##n## is total number of electrons moving in...

I've already solved the orbital speed by equating the kinetic and potential energy in the circle orbit case. $$\frac{1}{2}mv^2 = \frac{1}{2}ka^2.$$And so $$v^2 = \frac{k}{m}a^2$$Now when the impulse is added, the particle will obviously change course. If we set our reference point in time just...

I'm guessing this question can be solved using the law of conservation of momentum Vi = 5 m/s (5 m/s) M = (4.33 m/s) cos30 M + V sinθ M I don't know what to do after this... I'm also not sure if I use the sin and cos correctly.

Li = Lrf +Ltf Iωo = Iωf + mvRsinθ I = MR^2 (MR^2)ωo = (MR^2)ωf + mvRsinθ ωf = (MR^2ωo -mvRsinθ)/MR^2 = 3.99

A simultaneous measurement of both a particle's position and momentum may be successfully accomplished if more than one photon were utilized for the measurement. A non-demolishing measurement is possible if the emitters were aligned such that each would offset the other’s recoil of the target...

In Chapter 5.3, Ballentine uses geometrical arguments to obtain the initial magnitude of a hydrogen atom's bound electron momentum. How does equation (5.13) obtain? I tried to naively compute $$p_e^2 \equiv \textbf{p}_e\cdot \textbf{p}_e = p_a^2+p_b^2+p_o^2 + 2\textbf{p}_a\cdot \textbf{p}_b -...

Hi For an infinite well , solving the Schrodinger equation gives wavefunctions of the form sin(nπx/L). These are not eigenfunctions of the momentum operator which means there are no eigenvalues of the momentum operator. Does this mean momentum cannot be measured ? Inside the infinite well the...

Hi, Here is the problem What is required to answer this question is two assumptions. Firstly, the component of the momentum normal to the centre line is the same before and after. Therefore, secondly, A must recoil entirely in the horizontal plane. This is the only way to answer this question...

I understand how a massive, electrically charged spinning ball would have both angular momentum and a magnetic dipole, and i can see how the Stern–Gerlach experiment shows that the magnetic dipole of an electron is quantized. What kind of experiment demonstrates a connection between electron...

Why in order to derive the QM momentum operator we use the plane wave solution. Why later on in field theory and particle physics, the plane wave ansatz is so physically important?

Hi, I have a question. Let us say we have the wave function as with eigen value and base eigen value of: ##!\psi >\:=\:\frac{1}{6}\left(4!1,0,0>\:+\:3!2,1,1>\:-1!2,1,0\:+\:\sqrt{10}!2,1,-1>\right)## I need to find <Ly^2> the solution of the problem according to answers, is demanding that...

Cohen tannoudji. Vol 1.pg 702"Now, let us consider an infinitesimal rotation ##\mathscr{R}_{\mathbf{e}_z}(\mathrm{~d} \alpha)## about the ##O z## axis. Since the group law is conserved for infinitesimal rotations, the operator ##R_{\mathbf{e}_z}(\mathrm{~d} \alpha)## is necessarily of the form...

I was playing around, and I found something unexpected. If we are analyzing a simple fluid jet: We can apply Bernoulli's (which is Conservation of Energy) and arrive at: $$ P_{1_{B}} = \frac{1}{2} \rho \left( v_2^2 - v_1^2 \right) = \frac{1}{2} \rho ( v_2 - v_1 ) ( v_2+ v_1) $$ It would...

I calculated:arctan(fy/13.0)=55=>fy=18.566 m/s Then I calculated, using the momentum equation: m1viy+m2v2iy=(m1+m2)vfy=> mv2i=2*m*18.566=>v2=37.132 m/s I thought that because the cars were stuck together, the kinetic energy from the northbound car would be lost. So, the speed would have...

I understand that it is a 2D momentum problem with an elastic collision; Looking at the vector diagrams below, I notice that the velocity vectors initial and final in the y direction are in the same direction, indicating that momentum does not change, whereas the velocity vectors initial and...

I read that quantum spin is the measure of the angular momentum of a quantum object. Suppose you have a rotating Thing 1. Quantum objects bounce off of it then collide with Thing 2. Will this transfer angular momentum from Thing 1 to 2, causing it to rotate?

Mine is a simple question, so I shall keep development at a minimum. If a particle is moving in the absence of a potential (##V(x) = 0##), then ##\frac{\langle\hat p \rangle}{dt} = \langle -\frac{\partial V}{\partial x}\rangle=0## will require that the momentum expectation value remains...

Without helmet, m = 4kg, ##v_f = 10m/s## ##\Delta t = 0.0005sec## $$ \Delta p = mv_f - mv_i $$ $$ \Delta p_{without} = 40 kg m/s$$ $$ Impulse_ {without} = F_{net} \cdot \Delta t$$ $$ force_{without} = 80000 N$$ With helmet m = 4kg, ##v_f = 10m/s## ##\Delta t = 0.002sec $$ \Delta p = mv_f -...

For this problem, Why for part (a) the solution is, Is the bit circled in red zero because since the putty is released at a very small distance above the rod it velocity is negligible? Also for part (d) the solution is I did a computation of the initial and finial kinetic energies of the...

I feel like this should be pretty straightforward knowing all the equations involved but my brain seems be stalling for some reason.

Why do the Cauchy Stress Tensor & the Energy Momentum Tensor have the same SI units? Shouldn't adding time as a dimension changes the Energy Momentum Tensor's units? Did Einstein start with the Cauchy Tensor when he started working on the right hand side of the field equations of GR? If so, What...

For this problem I was very confused whether conservation of angular momentum should be applied to the person, the swing or the person-swing system. It seems to me that there is no net torque on any of the three systems I listed above. However, it seems that the angular momentums of the three...

Sorry for this beginner's question, but...if F=ma, then force is all about acceleration. But if vehicle A moving at constant velocity V hits a wall, and vehicle B moving at constant velocity greater than V hits the wall, then B hits the wall with greater momentum than A and does greater damage...

Hi, In my book I have and expression that I don't really understand. Using the definition of action ##\delta S = \frac{\partial L}{\partial \dot{q}} \delta q |_{t_1}^{t_2} + \int_{t_1}^{t_2} (\frac{\partial L}{\partial q} - \frac{d}{dt} \frac{\partial L}{\partial \dot{q}}) \delta q dt## Where L...