Questions tagged [energy-conservation]

The law of conservation of energy, which states that the amount of energy in a system is constant. For questions about Earth's environment, see the climate-science tag instead.

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Can a "Floppy Hammer" apply more force/energy than a regular hammer?

This is actually biased on a Meme: Floppy Hammer Know Your Meme But I was curious if we can actually prove if a floppy hammer applies more force/energy to a nail, than a regular straight hammer? (or ...
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Conservation of energy in quantum physics? [duplicate]

i was talking to a friend and he told me that in quantum field theory energy conservation doesn't hold and he gave me virtual particles as an example, is this correct?
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Electric car battery weight: understand question [closed]

Could you please assist an absolute beginner in understanding the core aspects of this problem and the relevant topics necessary for solving it, as well as specific of electric-car that should be used ...
renathy's user avatar
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How a tire send a car flying? [closed]

https://abc7news.com/118-freeway-crash-caught-on-video-los-angeles/13027476/ The incident happened on Thursday, March 23, in Chatsworth, Los Angeles. In which a vehicle went flying into the air after ...
Juan Carlos Oropeza's user avatar
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Violation of momentum and energy?

Current situation: a bullet is fired towards a block that is connected to a string which is connect to a ceiling. The bullet is embedded to the block and the object(block+bullet) swings up to a ...
Mohammed golfa's user avatar
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Is conservation of energy a local law in Quantum field theory? [closed]

From Wikipedia, "The local energy conservation in quantum field theory is ensured by the quantum Noether's theorem for the energy-momentum tensor operator. Thus energy is conserved by the normal ...
KleinMoretti's user avatar
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Energy and momentum conservation on a vertex in a time-ordered diagram and in a Feynman diagram

I read in the book Modern particle physics(page 114-119) from Mark Thomson that for a time-ordered diagram, the energy at each vertex is not conserved, but the momentum is. Furthermore, the energy-...
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Hawking radiation: what does a new external particle have to do with the mass of the black hole?

This question has been asked a few times here in a few different ways but the answers don't quite seem to land for me. Considering the virtual particle pair; one falls in, one escapes, both become ...
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Microwave oven efficiency and conservation of energy

Wikipedia says that microwave ovens can be around 50-64% efficient at converting electricity into microwaves. Where does the energy lost at this stage go? And how much of the energy that is ...
Karl's user avatar
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Elastic collision between 2 particles in 2D [closed]

A particle with mass $m_1=m$ moves along the x-axis at a velocity of $v_0$ and collides with another particle $m_2=4m$. As a result of the collision $m_1$ travels upwards at an angle of $90 ^\circ$. (...
Bad Hombre's user avatar
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Solving a problem using energy conservation doesn't work [closed]

Hello I'm trying to solve the following problem as I'm preparing for physics olympiads: The solution they gave involves finding the forces acting on the cylinder and hence finding acceleration, which ...
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How does relativistic Doppler effect conserve energy?

Say I have a laser traveling at the stationary observer at relativistic speed, so the laser wavelength gets blueshifted. To conserve total energy emitted, according to the observer, the laser emits ...
Meatball Princess's user avatar
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Where does a body get its energy to heat up when falling from height $h$?

When a body falls from a height $h$ it loses some energy to the surroundings, is it the energy that is lost to the surroundings that increases its temperature on the remaining energy that is stored in ...
Ritsu's user avatar
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Energy loss due to Cherenkov radiation

I'm trying to find a formula for (or some sort of direction towards approximating) the energy lost by a ultra relativistic positron when traveling through a cherenkov detector but I can't seem to find ...
Aiden.6's user avatar
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Why is the calculation of the semimajor axis of an orbit negative?

Say an object with an initial kinetic energy $\frac12 mv^2$ is launched from the surface of the Earth into an elliptical orbit with area $\pi ab$ without loss of energy. ($a$ is semimajor axis, $b$ is ...
Max0815's user avatar
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Where does the energy come from to cause Coriolis effect?

I read that the rotation of Earth on it's axis caused the deflection of wind along the equator but the air and the Earth are moving together so where do the energy comes from to produce coriolis ...
user6760's user avatar
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Why does my perpetual CMBR rocket ship not work? Why does the CMBR have infinite energy?

Take a spaceship and accelerate it to 99.947% the speed of light, effectively blueshifting the Cosmic Microwave Background (CMB) from 1.9mm to 500nm, turning the CMB to a harvestable source of energy. ...
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Is fuel cell efficiency limited by thermodynamics?

Let's say we have a mixture of oxygen and hydrogen gas, initially at room temperature and pressure. This mixture can be used to perform work: we can burn it, using the resulting heat as a source in a ...
Kotlopou's user avatar
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At what angle should an object be thrown to get it into orbit?

Yes this question is on the internet and has a lot of answers but they all suggest orbital velocity in an ideal circular orbit. I want it for an elliptical orbit. I have a few questions and ...
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What is the origin of energy emitted as radiation by an electrically charged object stationary around a massive object?

Einstein's special relativity tells us that laws of physics are the same in all intertial frames. General relativity futher extends this by stating that reference frames that are in free fall around ...
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Energy and Non-conservative forces

I understand that one cannot assign a potential energy to all points in space in the presence of a non-conservative force field due to the work done by the force being dependent on the path taken. ...
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Elliptical orbits and Hohmann transfer

I had a rather theoretical problem with the elliptical velocity equation while glancing the formulas and proofs. While doing the proof there was a statement of energy conservation : $$K.E.+P.E.=M.E.$$ ...
Star Gazer's user avatar
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Where does the energy go in inelastic collisions?

Chabay and Sherwood write in Matter and Interactions on page 406 about sticking collisions: We'll consider an inelastic collision in which a truck and a car collide in an icy intersection and stick ...
Julia's user avatar
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What’s wrong with this idea for an energy generator? [closed]

Okay I know a perpetuum mobile is impossible, so I think this should be wrong. I thought about heat pumps with a COP of 3.5, which is like 350% efficiency compared to a simple electrical resistor. Now ...
user1009013's user avatar
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Is energy only conserved statistically in quantum mechanics?

I know that a system's energy can be measured with an energy that can be below or above the expectation value, if the system was not in an energy eigenstate, so that energy is only conserved on ...
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2 answers
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Forever Pure Rolling? [duplicate]

If a spherical body is given some velocity and it then starts pure rolling on a plane surface(not inclined), will the body come to rest if we ignore other factors like surface irregularities and air ...
Shubham Kumar's user avatar
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2 answers
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Newtonian mechanics doubt

While solving a particular classical mechanics problem , I was told that for a system of particles to be bound under their mutual forces, their initial energy (With Respect To the COM) must be less ...
tensorman666's user avatar
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1 answer
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Is the motion of a billiard ball time reversal invariant?

Consider the motion of a billiard ball on two different billiard boards. One board is frictionless and another is not. The magnitude of the friction force of board on the ball is proportional to the ...
Brownian_Motion's user avatar
1 vote
1 answer
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If a block attached to a spring fixed at one end is given a velocity perpendicular to the spring, will the spring eventually stretch?

Consider an ideal spring which is fixed to the ground (frictionless) at one end, and has a block (of mass $m$, say) attached to it at the other end. When the spring is in its natural length, the block ...
brainfreeze's user avatar
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Why is the work done by moving an object up vertically not greater than mgh

Watching Walter Lewin's classical mechanics. In lecture 11 he says when moving object up vertically distance h, the work done by gravity is -mgh, which makes sense. But then he said the work done by ...
Erick Hernandez's user avatar
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If $v$ doubles, what will the value of $h$ be? [closed]

So, I came across this problem: A skier goes from position A to position B, and then in B, rises again. What must be the height ($h$) for the skier to reach B with double the velocity. I can't seem ...
Manuel's user avatar
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-2 votes
1 answer
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Destroying the Earth with balloons [closed]

Here's a fun idea. It costs 100 J to inflate a 1 kg Ballon. The balloon reaches 10 km in height which is a potential energy of: $$G^2 \times 1 \ kg = 10 \ kg \ m/s^2$$ Times 10 km is 100 kJ. The ...
Jose Garcia's user avatar
2 votes
3 answers
189 views

Describe the characteristics of a Hamiltonian System to a non-scientist

A Hamiltonian system is a dynamical system driven by a Hamiltonian $H$, i.e. $$ \dot{q}=\nabla_p H,~~~~ \dot{p}=-\nabla_q H. $$ These systems have nice properties like being symplectic as well as the ...
Monty's user avatar
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How do I calculate the $v^2$ part of the air resistance $(1/2)CpA$ into constants that will fit my general equation

I am currently working on an applied maths project in which I have modeled the forces at play when a rollercoaster travels down a slope and comes to a stop over a distance $d$ with the use of brakes. ...
Loch S's user avatar
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1 answer
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How does $H=U+PV$ come up when its definition never talks about such equation? [closed]

For first law of thermodynamics, what the law states can be matched with the equation, U=q+W , could anyone provide me insight on how does H=U+PV equation comes up? What is the physical meaning of H ?
Chethas Pai's user avatar
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Does the energy output of a piezoelectric material increase when its dielectric constant is incressed?

According to the output voltage equation, the output of a piezoelectric material increases when its dielectric constant is increased. But it reduces the coupling constant. Since that can we directly ...
Kavindu Lochana's user avatar
4 votes
1 answer
306 views

Confusion in the validity of First Law of Thermodynamics

Suppose a diathermic movable piston separates an adiabatic container into $2$ parts. Thermodynamic parameters of gases in the two parts are $p_1,v_1,t_1$ and $p_2,v_2,t_2$. We assume quasi static ...
KPS's user avatar
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2 answers
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Is 4-momentum conservation used in this answer?

In Dale's answer to the collision rest mass problem, how is he concluding that the momentum 4-vector of the resulting particle is equal to the sum of the 4-momentums of the incoming particles. I am ...
JohnA.'s user avatar
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1 vote
1 answer
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Conservation of Kinetic energy in splitting

If a stationary mass $M$ explodes into 2 masses $m_1$ and $m_2$ with velocity $v_1 $and $v_2$ respectively releasing no energy in any other form like sound and heat. Then I've read that- intial k.E = ...
Amit Rai's user avatar
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1 answer
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Using directed centrifugal force to create continuous acceleration [closed]

This is something that I've been curious about for a while now, and please understand I'm not a physicist by trade. I began this thought experiment thinking about how I've seen vibrations generated in ...
rubixibuc's user avatar
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1 vote
0 answers
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When will an electron fired at a proton be captured instead of scattered?

Suppose electrons of energy $E>0$ are fired toward a proton. Since energy is always conserved in a central motion, and because an electron bound to a hydrogen atom must have negative energy $(E<...
Solidification's user avatar
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Efficiency of an oscillating system of springs in series

Suppose we have a system of two or more springs in series which support a mass. If the system is subject to an instantaneous longitudinal force causing the springs to oscillate, how does the ...
POD's user avatar
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1 answer
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Relativistic speed of two elastically colliding particles

In section 16-4 Relativistic mass of The Feynman Lectures on Physics relativistic mass is discussed with an example of a collision between two equal mass particles. Frames: Observer 1: stationary. ...
ERP's user avatar
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1 vote
1 answer
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Potential energy of a permanent magnet

A friend and I had a discussion about the potential energy of a permanent magnet, and we want to find out which of our views is right, but we can't seem to find information to confirm/disprove either ...
nanocat's user avatar
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1 answer
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Relativistic conservation of momentum

In section 16-4 Relativistic mass of The Feynman Lectures on Physics relativistic mass is discussed with an example of a collision between two equal mass particles. While discussing the example from ...
ERP's user avatar
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0 votes
4 answers
142 views

Potential energy being converted into kinetic energy

It is said that the potential energy gets converted into kinetic energy for a freely falling body. But when a freely falling body comes to rest, that is, the velocity becomes 0, does the object still ...
Arsheen Syeda's user avatar
1 vote
0 answers
76 views

Calculating $C$ in $I_{CM} = CMR^2$

I am a bit new here, so please excuse any errors I might make. I am a student in an AP Physics C: Mechanics course and I am conducting an experiment where I am experimentally calculating the C values ...
Wizzrobe's user avatar
1 vote
3 answers
64 views

The lowering of a block using a spring and the net work done by each force involved

A spring hangs vertically in its relaxed state. A block of mass m is attached to the spring, but the block is held in place so that the spring at first does not stretch. Now the hand holding the block ...
Shiven Pradeep's user avatar
0 votes
0 answers
20 views

Systematic drift in total energy in MD simulation

I have been simulating a system of 10 particles interacting among themselves via Yukawa potential using Molecular Dynamics technique. In addition to the Yukawa interaction, there is an exterally ...
bubucodex's user avatar
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When an electron and a positron annihilate each other are they deleted from existence entirely? Does this follow the conservation of energy?

When an electron and a positron annihilate each other and release gamma rays, is that just changing the energy into something else (following the conservation of energy), or is energy actually being ...
Foutch Levi's user avatar

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