Conservation Definition and 999 Threads

Homework Statement Homework Equations W spring = 1/2kx^2 Ug = mgh The Attempt at a Solution I have the work in the above problem, but I'm kinda confused how there is any potential energy here besides the spring potential energy that we get in the final state. Why is mgh here mgx? why can h...

Hi everyone, hopefully someone will be able to point me in the right direction with this problem, I get as far as combining the two equations together and no matter how I rearrange them they don't seem to cancel nicely and leave me with an awful quadratic, I can find vx, but the question...

Homework Statement I'm sorry but I don't have the exactly problem written down but I know the givens. So the question involves finding work done on a pendulum hanging from the ceiling. Homework Equations I was given the the length of the string is 1m. That a mass hangs at the bottom of...

Hello everyone, For some time I'm a little bit confused about (at the first view) a very simple question, which is about the conversation of the energy of moving objects (in terms of special relativity). As an example let's talk about firearms. If the mass of the gun M1 is infinitely higher...

I was reading some articles about Casimir effect. It turns out that some virtual particles are created and suddenly disappears amd that these particles can exert a pressure on the plates. It seems that this creation breaks energy conservation law, but it cannot be.I would like to know which...

Derive equation v= √((2gh)/(1+.5(m/M)(r/R)^2)) by applying conservation of mechanical energy. A string is attached to a hanging mass and wrapped around a small cylinder. The hanging mass is released from rest from an initial height (h) and accelerates to the floor. The theoretical velocity (v)...

Homework Statement Lee is riding on her 6 kg skateboard with a constant speed of 2 m/s. She jumps off of her skateboard and continues forward with a velocity of 4 m/s relative to the ground. This causes the skateboard to go flying forward with a speed of 18.5 m/s relative to the ground. What is...

Homework Statement I need to find the intial velocity of a ball, given the angle the pendulum bob swings through. I need to derive this equation. [/B] V0=4.43mtotalL1/2{1-cosΔθ}1/2/mball Homework EquationsThe Attempt at a Solution I have barely any attempts since I can't even think where to...

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 Using conservation of energy, show that the 4-velocity ##u^{\mu}## of dust satisfies: ##u^{\mu}\nabla_{\mu}u^{\nu} = f u^{\nu}## Explicitly identify ##f##, which is some function of ##u^{\mu}##, ##\rho## and their derivatives. And show that this equation becomes...

I am finishing up a lab write up for conservation of energy, where we launched a projectile into the air and measured the initial velocity and height of the projectile. ( 10 trials) One of my questions asks if I wanted the ball (projectile) to travel twice as high, how much faster would it have...

Hello! I read that natural processes are invariant under CPT (based on some theorem) and that CP violation was observed experimentally. So this would mean that there are processes that are violated under time reversal. However, based on Noether theorem, this would mean that the energy is not...

Homework Statement "Consider a 250 gram block on a 10 degree frictionless incline and in contact with a spring of constant 1.2 N/cm. If the block is launched from rest by the spring with an initial compression of 6cm, how fast is the block moving at the point of release from the spring? How...

Hi everyone, I was watching Susskinsd's lectures posted on youtube about Quantum mechanics and he started explaining his -1st basic law of physics saying: the conservation of information means basically that if you start with 2 quantum states (vectors) which are observably different, or...

Homework Statement The reaction dd → απ0 (where α is the Helium-4 nucleus and d denotes the deuteron) has never been observed. Why? Homework EquationsThe Attempt at a Solution [/B] So I checked first the masses to make sure energy/momentum are conserved and found out that mass of 2d is...

Is it accepted that the law of conservation of energy can be considered in a non-local context? If this is not accepted, then why not?

Dear Everybody There is a ball which has mass of 11 grams is thrown straight up with an initial speed of 4 m/s. Assume the air drag is negligible. a. What is the kinetic energy of the ball (in J) as it leaves the hand? b. How much work is done by the gravitational force during the ball's rise...

Homework Statement I am asked in a lab report to explain the conservation of power in the armature circuit of the DC motor. Homework Equations This is the data I have acquired: The Attempt at a Solution I have been reading around, and I have learned somewhat about the Armature Copper Loss...

1. Two identical charged particles which are point masses are fastened to the two ends of a spring of spring constant 100 N/m and the natural length 10cm.The system rests on a smooth horizontal table.The charge of each particle is 2*10^(-8)C.the extension of spring if the extension is small as...

Homework Statement A two-stage rocket is traveling at 4500 m/s before the stages separate. The 3000-kg first stage is pushed away from the second stage with an explosive charge, after which the first stage continues to travel in the same direction at a speed of 3000 m/s . How fast is the...

Homework Statement [/B] A rocket that starts at rest with mass M ejects exhaust at a given speed u. What is the mass of the rocket (including unused fuel) when its momentum is maximum? What is the mass when its energy is maximum? Homework Equations [/B] p = mv The Attempt at a Solution...

I go to work on the train and I get on at the back and get off at the front. I can choose when to walk through the train. If I walk when the train is accelerating forwards it is harder for me to get to the front and I do more work. If I make the trip when the train is stopped or at a constant...

Hi, all and thanks for your time. I did read that the conservation of Buoyancy is an "alternative" conservation of energy under some hypothesis. Can someone explain how do I start from the conservation of energy and find the conservation of buoyancy? Are there some corresponding mathematical...

Homework Statement We did a lab where we had one cart with an unknown mass stationary on a friction-less surface. Another cart with a mass of 378.9g, was pushed down the track (which moves at a constant speed due to the friction-free surface) and collides with the second cart - so it is a hit...

Homework Statement My textbook states: Since the number of particles of dust is conserved we also have the conservation equation $$\nabla_\mu (\rho u^\mu)=0$$ Where ##\rho=nm=N/(\mathrm{d}x \cdot \mathrm{d}y \cdot \mathrm{d}z) m## is the mass per infinitesimal volume and ## (u^\mu) ## is...

γ+2D ----> 1H + 1n In this photonuclear reaction, is it possible to write the momentum balance equation as it follows, MHvH = Mnvn It somehow seems to wrong to me, since the incoming photon has a certain momentum, which is not taken account in the balance equation. Thank you in advance.

1. The problem statement, all variables, and given/known data Describe the energy conversions in a spring undergoing simple harmonic motion as it moves from the point of maximum compression to maximum stretch in a frictionless environment. Focus on points at which there will be maximum speed...

Homework Statement The luminosity of the star is defined as ##\phi = L/4\pi r^2## The photons from the star hits the sail of mass ##M## and cross sectional area ##A##. What's the final velocity of the sail after getting hit by photons for a small time t? Assume the collision is elastic and the...

A pet mouse sleeps near the eastern edge of a stationary, horizontal turntable that is supported by a frictionless, vertical axle through its center. The mouse wakes up and starts to walk north on the turntable. Is the momentum of the system constant? i understand that the initial momentum is...

Homework Statement Assume two masses m1' and m2' are moving in the positive x-direction with velocities v1' and v2' as measured by an observer in S' before a collision. After the collision, the two masses stick together and move with velocity v' in S'. Show that if an observer in S' finds...

1. Homework Statement ( This question is from the textbook of Introduction to Elementary Particle Physics, written by Griffiths, on the problem set of Chapter 3 ) Particle A (energy E) hits particle B (at rest), producing particles C1, C2, ...: A + B → C1 + C2 + ... + CN. Calculate the...

Homework Statement Given a horizontal rod (parallel to x axis) and two disks attached near its ends symmetrically. The rods and disks are perfectly balanced i.e. the disks have same mass and density. The system's center of mass is exactly at geometric center of the rod (since its balanced)...

I believe that conservation laws, like for energy and momentum, are obeyed during the particle decay process, e.g. the total energy of the new output particles is equal to the energy of the one input particle. But is that relationship subject to quantum fuzziness? Suppose we, somehow, prepare...

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...

I am not sure if I am at the right place and I hope that I am... For my EE I want to do an investigation on something related to pool table and games so it will definitely be related to momentum. And one of the common techniques in pool games is that the player aims the ball on the rail of the...

I have a few questions: Can a u quark turn into a d quark (heavier) via the weak interaction? If so, how is the mass/energy shortfall made up? How can the (supermassive) carrier bosons (W, Z) be called into being? Where does the energy come from? Or is the energy bill unpaid because they are...

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 Given 2 magnets of equal weight (w0) and each with a magnetic strength (t0) placed inside a straight hollow cylindrical tube. One of the magnets is attached to one end of the tube and the other magnet is free to move inside the tube. The other end of the tube is open to...

As a spinning mass is unwound, angular momentum is conserved, meaning ##Iω## remains constant. However, since rotational energy is proportional to the square of the angular velocity, how is it possible for energy to be conserved as well?

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...

From what I can read on the web, it seems poeple don't agree wether or not dark energy violates conservation of energy. For some, as dark energy density is constant and the Universe expands, the total energy grows. For others, that growing energy is compensated by a growing negative...

Homework Statement A 220-kg beam 2.8 m in length slides broadside down the ice with a speed of 23 m/s . A 68-kgman at rest grabs one end as it goes past and hangs on as both he and the beam go spinning down the ice. Assume frictionless motion. (Figure 1) Homework Equations L1=L2 Iω=L The...

As I understand it, the ratio of the electric field strength to the magnetic field strength at any point in a propagating electromagnetic plane wave is equal to the speed of light. How can the electric and magnetic field be perpendicular to each other yet still validate the E = cB equation? A...

Homework Statement A two-ended "rocket" is initially stationary on a frictionless floor, with its center at the origin of an axis. The rocket consists of a central block C (of mass M=6 kg) and blocks L and R (each of mass m = 2 kg) on the left and right sides. Small explosions can shoot either...

Homework Statement I saw this problem from a few years ago here on Physics Forum (https://www.physicsforums.com/threads/work-energy-theorem-problem.823990/) and wanted some clarification. Here is the problem: A curved plate of mass M is placed on the horizontal, frictionless plane as shown...

Homework Statement Hey all, another problem. There is a 1 meter wooden panel that is on a frictionless surface. A puck is placed on one end of the panel and is pushed towards the other side. The mass of the panel is 10 times that of the puck. Also, there is a friction coefficient of uk=0.15...

Homework Statement Two blocks are connected with a massless, non-stretchable rope, and connected to a spring that is fixed to a wall. One of the blocks is hanging from the side of the table, while the other lies on the table. The mass of each block is m=1.0 kg, spring stiffness is k=50 N/m...

I am trying to understand how energy is conserved in a magnetron. If the electrons are following a circular path in the magnetic field and never reach the anode will there be zero current between the anode and the cathode? If so how does the device consume power from the external circuit...