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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Do Maxwell's equations conserve energy? [closed]

I was wondering if Maxwell equations conserved energy. Jackson is not really convincing about the whole Poynting theorem (neither currently google found articles which just assume a bunch of stuff). ...
96 views

Where does energy go when it is used against itself?

Suppose a ufo can convert fuel into kinetic energy with 100% efficiency. The ufo travels forwards some distance and then back in the vacuum of space. The ufo stops and has returned to it's original ...
50 views

In this energy conservation problem, why are the answers different with different units? [closed]

Really basic question, but basically I'm given a change in height in centimeters (that's how I measured it). From that, I'm supposed to find the initial kinetic energy. $KE_i = PE_f$ After doing ...
1k views

Infinite acceleration

Let's say we have two planets at a stand still within reasonable distance of each other. They will accelerate towards each other and subsequently collide. If instead we give them a sufficient (but ...
1k views

When we catch a falling object, where does its kinetic energy go? [duplicate]

Some of it is transformed into heat and noise, but where does the rest go? Further details: The object does not bounce off (e.g. a sack of rice marble ball). The hand remains completely static ...
67 views

Where is the extra heating value of coal compared to the original wood coming from?

My question is about the formation of coal seeming to break the laws of the conservation of energy (that energy can neither be created nor destroyed but instead transferred from one thing to another). ...
73 views

How to identify if the law of conservation of energy is violated in a nuclear reaction? [closed]

I have encountered many textbook questions that ask for what laws of conservation is violated in a given nuclear reaction, and I can't seem to figure out how to identify if a nuclear reaction violates ...
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Minimising the time of an object falling under gravity? [closed]

The first step of this task (the only step I am actually stuck with), is to prove that the time taken for an object to fall between two points, O and A, is given by: \Delta t~=~\frac{1}{\sqrt{2g}}\...
154 views

Why does this not make infinite energy?

Here's an idea I had for infinite energy: Get into a spaceship, and fly to a star or other large body and get into orbit. Then just harvest your kinetic energy somehow and keep going indefinitely. My ...
1k views

Calculating energy needed for by a car climbing a slope [closed]

I'm having a difficult time answering this question. I think I'm just converting the units wrong somewhere: You're the CEO of a courier company, and you decide to select an electric car for your ...
287 views

Conservation of energy

I have given one-dimensional motion of the particle directed horizontally. A problem says: "...Show that for this given motion Conservation of Energy Law holds.". Since Energy can intuitively be ...
151 views

How exactly, or whats the process, rather, of energy changing into matter?

$E=mc^2$ this is the equation by Einstein claiming energy can change from energy to mass. this would happened at the big bang I assume, when electrons and protons were made to create hydrogen and some ...
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Difference between the work done by three masses on different situations

We have 3 particles, with mass $m_{i}$ What's the difference between: i) Putting each one in a positión $x_{i}$ one by one, and ii) Putting the three at the same time in positions $x_{i}$, in both ...
113 views

Conservation of Energy for Uniform Circular Motion in a Vertical Plane [duplicate]

I was considering the energy and work done on an object experiencing uniform circular motion in a vertical plane, eg. a ball on a string swung vertically, and I arrived upon these conclusions: The ...
40 views

What is the largest radius that the circular track can have such that the car remains in contact with the track? [closed]

A car is travelling at $u$ as it enters a vertical loop of radius $r$. What is the largest value of $r$ that the track can have such that the car goes up and around the track whilst remaining in ...
135 views

Conservation of energy conditions

I know this question might sound silly, but I just started learning physics and struggling to understand when energy is conserved. The statement "When there are only conservative forces on (or in?) ...
846 views

Is “Total Energy = Kinetic + Potential” always true in a harmonic oscillator?

Consider a object executing simple harmonic motion in one dimensions due to a variable external force (like a spring maybe). I like to think that at any point in it's motion at any time the mechanical ...
221 views

Linear Superposition Principle vs Energy Conservation during propagation of EM waves

Think about focusing an EM beam, and having a divergent beam past the focus. Let r be the distance from the focus to a measurement point. The Linear Superposition Principle implies that the electric ...
96 views

Is it possible to make a scooter that is propelled by perpetual magnets (without converting it to electricity)? [duplicate]

I am, along with two of my classmates, are planning to make a prototype of a scooter (as in slower, smaller version of a motorcycle) that is propelled by an infinitely turning magnet wheel. Not as a ...
100 views

Is there any danger of gravity being used up? [duplicate]

Posit a way to harness gravity for energy and widespread use of this new technology world-wide. Could it be damaging to Earth, over a few hundred years, slowing or speeding up rotation or the orbit ...
90 views

Supernovas create energy?

Ok here we go. Supernovas do have to have energy spent to explode, that is known. That explosion power also equals to the energy spent to cause said explosion, this is also known . Besides creating ...
223 views

Energy carried by photon not conserved?

In an imaginary frame of reference traveling with a photon, the length of the path traveled is 0. If the length of the path is 0, isn't it similar to say that the photon is either at the source or at ...
196 views

Is the mathematical truth 1+1=2 analogous to the conservation of energy? [closed]

They seem to express the same concept in different fields.
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If there were no inertia would perpetual motion be possible? [closed]

Is it not inertia that makes a flywheel resist being put into motion? And if that is true, is inertia a consequence of being unable to create energy, i.e., why perpetual motion machines do not in fact ...
1k views

Why can't rotating magnets in space or zero gravity be used to create infinite energy? [closed]

I would like to know if a system like the one below will possibly work. I understand that the laws of physics forbid the "creation" of energy but despite my efforts I haven't been able to figure out ...
38 views

Why is zero-point energy idolized as a good source of energy? [closed]

I've really only seen it in like liquid helium and I don't understand how it can hold the potential portrayed in the incredible movie by the main villian
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Can total internal reflection be used to create a source of light which will never be used up?

I am a science student and was thinking of something great for a science model , Thought of this, please tell me will this work and also suggest some other ideas that can be used to make good working ...
548 views

Oscillation of a simple pendulum [closed]

What is maximum possible time period of oscillation of a simple pendulum on earth? Please elaborate your answers.
2k views

Will spinning DC motor in space generate infinite energy?

If I take a DC motor far in space and spin it, will it continue to spin forever and generate infinite electrical energy? If so, then won't it violate law of conservation of energy?
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Do you know the principle which says that connecting two sources of similar kind produces a waste and destruction? [closed]

There is a great article, called commutation cells, which states that you cannot transfer kinetic energy from one container to another immediately, bypassing the potential energy storage. Otherwise, ...
327 views

Explain this contradiction of violation of “ energy conservation ” using classical mechanics

Consider a rocket moves upward with some acceleration for a very small time say '$dt$' then the kinetic energy increases (for acceleration). as well as as the potential energy increases (due to height ...
696 views

Does the big bang violate the conservation of energy? [duplicate]

It is a fact that a thing is existing now because it had already been created. So why don't we take this to account to redefine law of conservation of energy.
155 views

Conservation of energy in the form of y=kx +b?

I am doing an experiment on method of mixtures and specific heat capacities. During my experiment I have to use the graph as a means of finding the SHC of the subject. So I did the experiment with ...
183 views

Does mass of universe at the moment of big bang changes compared to present day? [duplicate]

Empty space isn't empty as it can contain energy in terms of quantum fluctuation, so since inflation I like to know whether if the present day universe has put on weight?
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Is there a ball that bounces higher past the point that it is dropped? [closed]

Is there a ball that bounces higher than the point it is dropped?
399 views

Searl effect: myth or reality? [closed]

Recently I heard about Searl effect. Allegedly, this generator produces "free" energy, and that John Searl was accused of stealing electricity, but in fact he provided the entire laboratory with ...
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If I spinned a fan in a vacuum it will keep spinning forever. Why can we not make energy out of it? [duplicate]

Suppose we created a vacuum and spinned a turbine inside it with some amount of force. According to newton's second law it will keep spinning as there is no air resistance, so why can we not make ...
757 views

Shawyer EM Drive — Momentum Conservation Violation [duplicate]

I have been following the developments around the Shawyer EM drive for about 2 years now as NASA and other parties test it out in various environments. To preface, I would very much like to see the EM ...
55 views

Perpetual Motion Machine 1: Magnetic Superconductor Loop Generating Energy with Piezoelectrics [closed]

I know there are a lot of perpetual motion machine designs out there, but I haven't found one that looks like this one. I will use this diagram. Assume the entire ring is made of a superconducting "...
304 views

What is wrong with my perpetual motion machine model? [closed]

I know that perpetual motion machines are not possible and I want to know the reason why will this machine not work. The Car B has a magnetic bulge on top of it and Car B can only move forward. It ...
4k views

Is there kinetic energy when speed is constant? [closed]

When an object is moving at a constant velocity, then does it have kinetic energy, or since kinetic energy is the change in motion, it doesn't?
635 views

Auto spinning turbine generator

This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how ...
462 views

Is kinetic energy of a system conserved during bomb explosion? [duplicate]

Conservation of momentum is a very obvious thing, but I can't figure out if kinetic energy would be conserved or not. You can think in two ways: Initial kinetic energy is zero and final kinetic ...
102 views

Possible Perpetual motion? [closed]

I have an idea for a perpetual motion machine that I came up with and need answers as to what may be wrong with it. Consider a molecule made of several atoms, and apply a rotating magnetic field ...
596 views

Simple harmonic motion, maximum kinetic energy [closed]

Why kinetic energy is maximum at mean position?
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Block sliding down an inclined type of energy transformation [closed]

when we have a box sliding down a ramp, does the gravitational potential energy directly transform into internal energy? I mean doesn't it firstly turn into kinetic energy then turns to internal ...
103 views

Why is it necessary to supply constant electricity to make a laser work?

As we know that in lasers there are excited atoms. When energy is provided in the form of light, heat or electricity to these atoms, these excited atoms after sometime go to a lower state of energy ...
895 views

Why don't we have free energy generators? [closed]

Why can't you create energy out of nowhere For me it's not enough that a smart guy for hundreds of years said so. Some scientists and religious people said that the earth was flat - untill someone ...
The two magnet pairs $N_2$ and $S_2$, $N_1$ and $S_1$ attract each other respectively which causes the wheel$_1$ to move in the clockwise direction and wheel$_2$ to move in the anti-clockwise ...