Energy conservation Definition and 434 Threads

Homework Statement In the given figure, a wedge of mass 2m is lying at rest on a horizontal surface. The wedge has a cavity which is the portion of a sphere of radius R. A small sphere of mass m is released from the top edge of the cavity to slide down. All surfaces are smooth.Prove the maximum...

Homework Statement 2. Homework Equations Conservation Mechanical Energy The Attempt at a Solution I need to find how close to the wall the block will come. Since there's no friction, I presumed there'd be enough energy, and only enough energy, to go the same distance d to the left of A...

Hello! I read some stuff about "attempts" to test some aspects of string theory at LHC and I was wondering if there is any deep reason behind the conservation of energy in general or it is just based on the fact that it holds in all the experiments (excluding uncertainty principle arguments)...

Homework Statement https://moodle.telt.unsw.edu.au/pluginfile.php/2296810/question/questiontext/2691158/6/1668509/cart%20track.png A block of ice (that we shall treat as a particle) slides with negligible friction or air resistance on the curved tpath sketched (black line). The mass of 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 [/B] Two blocks are connected by a string that passes over a massless, frictionless pulley, as shown in the figure. Block A, with a mass mA = 4.00 kg, rests on a ramp measuring 3.0 m vertically and 4.0 m horizontally. Block B hangs vertically below the pulley. Note that you...

Let's assume that a system has zero total momentum. The following relationship between mass and energy should apply: E=mc^2. If a system is overall at rest, does that mean that any internal changes to that system, assuming they leave the system with non-negative mass, will not be able to...

Homework Statement A particle of mass M and 4-moment P decays into two particles of masses m1 and m2 1) Find the total energy of each particle (lab frame). 2) Show that the kinetic energy T1 of the first particle in the same reference frame is given by $$T_1= \Delta M (1 - \frac{m_1}{M} -...

Hello, This has been bugging me for some time now, so I would be interested to see what I have been missing so far. Imagine a single ray of light (made up of many photons) hitting a perfectly non-absorbing (for this wavelength of light) spherical dielectric object, which has finite mass. The...

Homework Statement There are two elastic "superballs" of mass M and m placed on top of each other with a smal distance. The lighter ball of mass m is on top of the bigger ball of mass M. The balls are released from a height h and have velocity u when they hit the ground. Prove that the top ball...

Homework Statement Two identical particles of mass m travel towards each other at speed v; they combine and form a single new particle. By employing conservation of momentum and conservation of energy, what is the mass of this new particle in Homework Equations Relativistic momentum and total...

Homework Statement A hockey puck of mass M hits two other, identical pucks of mass m. The two pucks fly off with the same speed vf at angles of ±θ relative to the direction the original puck was traveling (see figure). The original puck had initial speed vi, and the two other pucks were...

The following problem is from Sears and Zemansky's textbook. A wooden rod of negligible mass and length 80.0 cm is pivoted about a horizontal axis through its center. A white rat with mass 0.500 kg clings to one end of the stick, and a mouse with mass 0.200 kg clings to the other end. The...

Homework Statement Homework Equations Conservative of energy mg(y2-y1) +1/2 k (s2-s02) = 1/2 mv12 +1/2 mv22 The Attempt at a Solution v1 = 0 at rest y2 = 0 bottom What I got is v2 = 8.20 m/s but not correct, I don't know how I can take into account the tension.. Fspring = -ks = -4000 N/m *...

Homework Statement Homework Equations U_initial = U_final The Attempt at a Solution K_0 = 10 m/s K_1 = 0 m/s (at peak) V_0 = mgh_0 V_1 = mgh_1 1/2 mv02 + mgh0 = 1/2 mv12 + mgh1

Consider a charged particle moving with velocity v, having the energy 1/2 m v^2. Now we deccelerate the particle very quickly; so quickly that the radiated energy is greater than the kinetic energy (it can be arbitrarily large). Note also that energy obtained from decceleration is positive...

Let's have waves with their carried power proportional to the square of their amplitude(s). The waves obey the principle of superposition. Before superposition, we can calculate the power output based on the amplitudes. After superposition, there will be new values for the amplitudes, but the...

Hello, I've got a problem and I have no idea how to start. I'll be happy for any hint. Thanks Homework Statement Two beads each of mass m are at the top (Z) of a frictionless hoop of mass M and radius R which lies in the vertical plane. The hoop is supported by a frictionless vertical support...

I'm trying to derive the conservaton of energy for electromagnetic fields with currents from the action principle, but I have some trouble understanding how the interaction term in the Lagrangian fits into this. The approach I have seen so far has been to express the Lagrangian density as...

I am not defying any law here just asking. Energy conservation. I was really wondering, How physicists arrived to this law? I was fine with it, solving problems and stuff. But sometimes things click in my mind. Perhaps confusionleads to a better understanding... We can prove mathematically...

How can you determine if energy was conserve in a momentum problem? Let's say a small mass "m" hits a larger stationary mass "5m" where the smaller mass "m" flies bounces upward and the larger mass "5m" bounces in a negative downward direction. So from them bouncing off each other I know that...

How is information conserved when one form of energy is converted to other? Like how a black hole's gravitational energy is used to create photon pairs near the event horizon, what happens to the information in the gravitational wavepackets (gravitons?) and how is it not lost?

Homework Statement The right answer is E, and I have no idea how to solve this problem. Please advise on how to proceed. Thanks in advance. Homework Equations conservation of mechanical energy?? The Attempt at a Solution Many attempts were done, but I am lacking on theory with this. How...

Homework Statement Homework EquationsThe Attempt at a Solution The answer to this problem can be obtained by equating ##\frac{1}{2}mv^2 = ΔU## . But I am not sure why this is to be done . In fact I think this is not quite right . 1) The Kinetic energy ##\frac{1}{2}mv^2## is the energy due...

In the example, is it possible to have same velocities at the two ends of the tube? How would you construct energy conversation equation?

1. A ball hanging on a pendulum hits an object standing on the table. The interaction is elastic and linear. After that, the object falls on the floor. Homework Equations From state 1 to 2, we have the conservation of the potential energy of the pendulum to its kinetic energy, right before...

I want to make a Newton Cradle. Just wondering how I can reduce the loss of energy so the balls keep bumping for a long time

Homework Statement Consider a massless rod of length $L$ with a small mass $m1$ attached on one end, and $m2$ attached on the other end. The rod is initially in the vertical position at rest on a frictionless surface, with $m1$ on bottom and $m2$ on top. A small impulse is applied to the top...

Homework Statement Three blocks of identical mass are placed on a frictionless table as shown. The center block is at rest, whereas the other two blocks are moving directly towards it at identical speeds v. The center block is initially closer to the left block than the right one. All motion...

Hi all, I have a small misunderstanding about the energy conservation in diffraction from 2 slits. First, I understand the energy conservation of interference from 2 slits. If intensity from each slit is I, then I have intensity of 2I after slits plane. Interference is given by: So at bright...

When a photon is emitted by an atom is the energy of the atom conserved?

Homework Statement The statement of the question is:A chain of uniform linear mass density ##\rho##, length ##b## and mass ##M## hands as shown in the figure below. At time t=0, the ends A and B are adjacent, but end B is released. Find the tension in the chain at point A after end B has...

Homework Statement An ice cube is placed on top of an overturned spherical bowl of radius r, as indicated in the figure. If the ice cube slides downward from rest at the top of the bowl, at what angle θdoes it separate from the bowl? In other words, at what angle does the normal force between...

I am modelling a 1D fluid wave propagation problem and I needed to know how I can check that my results are energy conservative. please reply, urgent. thank you.

Homework Statement A car of mass 1500kg is parked on a 30degree slope before rolling down a distance of 30m onto a flat section where it collides with a stationary car. The cars stick together and scrape along the road for 20m until they come to a rest. Calculate the velocity of the two...

Hi, Consider the conservation laws for an isothermal linear incompressible flow governed by the mass and momentum equation. The kinetic energy equation is then solved to see if energy conserved. Can anyone tell me if once it is shown energy is conserved, it implies that convergence is obtained...

Homework Statement A 226g block is pressed against a spring of force constant 1.25kN/m until the block compresses the spring 14.3cm. The spring rests at the bottom of a ramp inclined at 62.5° to the horizontal. Using energy considerations, determine how far up the incline the block moves before...

Homework Statement Find the horizontal distance the skier travels before coming to rest if the incline also has a coefficient of kinetic friction equal to 0.210. Assume that theta = 20.0°. Homework EquationsThe Attempt at a Solution

What happens to the energy of a laser beam when it completely deconstructively interferes with itself in a michelson interferometer?

One of the possible decay modes of the neutral kaon is ## K^0 \rightarrow \pi^+ + \pi^- ## The rest masses of the K0 and pion are 498 MeV/c2 and 135 MeV/c2, respectively. In 2-dimensions (xz-plane), if the kaon has an initial momentum of 2000 MeV/c in the z direction, what is the momentum of...

As i am a physics amateur and most of what i learned is through videos, i sometimes get confused about energy conservation, my question concerns particle acceleration in CRT for example, we create a potential difference ( which requires energy) between the anode and the cathode, then the...

In Lagrangian mechanics the energy E is given as : E = \frac{dL}{d\dot{q}}\dot{q} - L Now in the cases where L have explicit time dependence, E will not be conserved. The notes I am referring to provide these two examples to distinguish between the cases where E is energy and it is not...

Does energy conservation law still hold if the system contact with varying source of energy? Because in QM the Hamintonian of the system always commune with itself,so the conservation law still correct.But if it is,where is the exchange energy between the system and the enviroment?

Homework Statement Consider two photons, one with energy ε1 = 2MeV traveling to the right, and the other with energy ε2 = 3MeV moving tot he left. The two photons collide head-on and produce a positron-electron pair. Suppose the the electron and positron move along the same axis as the photons...

In my intro to Quantum Mechanics course, my professor gave a little aside while exploring the analogy between the Schrodinger Equation and Newton's second law: in classical physics, energy is conserved when the potential energy is not a function of time. I wanted to try to answer this my self...

Energy of beta ray and neutrino is equal Q=M(mass) of nucleous before-M of nucleous after,so it about 1Mev.But the mass of W boson is 80 MeV,so the least energy of electron and neutrino must be 80 MeV. Why there is the difference?Why does it seem that energy were not conservation?

I know a similar question has been asked but I'm still kind of stumped. Imagine the Earth on the left and a small mass to it's right separated by some distance h. You are in the frame of reference where the Earth and the small mass are moving to your right at some speed v. So, both the Earth...

A person has reached H height by 100J energy whereas by the use of pulley, the man can reach the height by a fraction of that energy. In this manner, it is reaching height H by giving off less energy than required by gravitational potential energy. So isn't the law of conservation of energy...

Okay, so I've had this question on wormholes which seems to have hijacked my mind from some time now, and what better place to bring it out rather than PF? A previous thread containing lots of lengthy posts was made here a few years ago, but I'm not getting a clear-cut answer despite leafing...

Skip to 29:50. Here Feynman is explaining how some laws are not independent of energy conservation. In this case he goes on to explain how instead of using the law of levers were can use energy conservation to see what weight an object needs to on one side be to balance (or be in a state where...