New answers tagged

-2

Well i think yes because we can change one form of energy into other form so sound is also a type of energy that's why its possible to change it into electricity......


0

Well there is two answers: 1. It is not infinite. At a point when the black hole has taken in lots of matter, it will throw some out of the black hole to again be able to take in matter.It is like the biggest foodie in the world who can eat a lot but at a point when his tummy is full, he needs to throw up or wait until he can take in more. 2. It is infinite. ...


1

Black holes are in the realm of General Relativity. In GR even the law of conservation of energy is under question when approaching singularities of the GR solution. Potential energy is a concept that comes with conservation of energy. Where the singularity in the black hole solutions is dominating, one cannot talk in terms of energy conservation and ...


2

Your question What is the potential energy of a black hole? doesn't make sense because energy is a somewhat tricky concept to deal with in GR. If we treat the black hole as fixed we can study the motion of a test particle falling into it, and we find that there is a quantity analogous to total energy that is constant as the particle falls in. So in ...


1

What would happen if you were to release the energies of the big bang in our universe a second time? Have a look at this standard history of the universe, History of the Universe - gravitational waves are hypothesized to arise from cosmic inflation, an expansion just after the Big Bang Our universe is now at the far right. Note the beginning ...


1

Heat transfer can occur by conduction, by convection, and by radiation. If you consider conduction through the bulk of the cup, the rate of heat transfer is directly proportional to the temperature difference across the material of the cup. As your experiment holds all variables equal except the temperature difference, cup A will lose heat at a faster rate ...


0

This is very similar to how plants capture CO2 and form "fuels" (sugars) to feed themselves. In the natural case, the energy comes from sunlight captured by the chlorophylls in the plant cells, and the chemical reaction is carried out by a group of enzymes (Photosystem I and Photosystem II). A lot of scientists are trying to replicate this process ...


3

Wood is a poor conductor Oven-Dry Wood has a resistivity of $1.00 \times 10^{14}$ to $1.00 \times 10^{16} \Omega m$ Damp Wood has a resistivity of $1.00 \times 10^3$ to $1.00 \times 10^4 \Omega m$ Copper has a resistivity of $1.68 \times 10^{−8} \Omega m$


2

The obvious method is to burn a barrel of crude oil and measure how much energy is released. The only slightly less obvious method is to burn a small amount of oil and measure how much energy is released, and then mathematically figure how much energy a whole barrel would release, as @CuriousOne points out. The latter method is superior in both the ...


4

As a general rule adding thermal energy doesn't cause electronic transitions. That's because typical electronic transition energies are a few electron volts or around 100kT at room temperature. In a metal the electrons aren't in discrete energy levels but instead reside in a continuous band of energy levels called the conduction band. While thermal energy ...


0

Visit http://www.science.uwaterloo.ca/~cchieh/cact/applychem/hydration.html You can see that the enthalpy of hydration is a two step proccess solvation and reverse crystallization, the ΔH(hydr) is actually positive so you have to give energy just to dissolve the NaCl in water, in order to seperate the water from the NaCl you need to account for the enthalpy ...


1

The small object exerts a force in the opposite direction to the normal force on the cart


0

Generators often have two sets of windings - one arranged on the stator (fixed) and the other on the rotor (spinning). One is chosen/designed to be the excitor (could be either the rotor or the stator); the excitor is fed a small amount of electrical power to maintain a magnetic field. The other winding generates the output as it moves through the field ...


1

Assume the power of the microwave oven to be $P$ and that the instructions for cake and custard lead to the same temperature ($T$) of both when they are heated separately, then: $t_1=\frac{m_1c_1(T-T_0)}{\epsilon P}$ and : $t_2=\frac{m_2c_2(T-T_0)}{\epsilon P}$ where in the indices $1$ and $2$ refer to cake and custard, $m$ the mass, $c$ the specific ...


2

The easiest way I can think of to get some idea of this is to sit by your water heater and listen to it. Assuming you (and no one else) has used any hot water recently (like, within the last hour or so), and that no one uses any more hot water for the duration of this experiment, then the water heater will turn on only to maintain a relatively constant ...


0

This is not a proper derivation. At a fundamental level, there are at least three important points that are not taken into account by this approach: as you consider a second mass point, it is somewhat difficult to adjust (in a non-arbitrary way) the derivation to obtain the correct energy term related to the angular momentum and/or rigid body rotation ...


5

Here is a flow chart of the forms of energy, with links . Conservation of energy is one of the fundamental laws governing physical systems and is the only reason why one can talk of "negative energy" here is a breakdown of the forms that **Conservation of energy ** takes In almost all frames negative energy exists, in the sense of conservation of ...


5

Photons mediate the electromagnetic force. Atoms are not necessary for photons to exist. You just need charged particles (electrons, protons, etc) to interact with each other from a distance. There are many ways for a photon to be created and destroyed. Depending upon its wavelength, as it propagates in free space , it could "disappear" and a pair ...


3

This is a common misconception. The function above can be interpreted as follows. Sound of frequency $\dfrac{\omega_1+\omega_2}{2}$ with amplitude modulated by the cos function of frequency $\dfrac{\omega_1-\omega_2}{2}$. The cosine function becomes zero twice every cycle as well as reaching a maximum magnitude twice every cycle. So the intensity of the ...


2

The energy of the collision is equal to the kinetic energy $K$ of the two bodys just before they collide. The mechanical energy is conserved during the whole process, so $$ V_1+K_1=V_2+K_2 $$ where $V$ is the gravitational potential energy of the bodies and $K$ their kinetic energy. Subscripts $1$ and $2$ refer to the initial time and the time of the ...


0

Kinetic energy's quadratic makes perfect sense if our reality is not actually first order in space, and is instead simply a measurement of the relative rate that an object is passing through time. The space of our existence then becomes the space of simultaneous time, at any given point in time, as it progresses. In this scenario, changing the kinetic ...


0

I don't really have the background to understand such matters, but this presentation by Alan Guth gave me at least some idea of what it means to say the energy of a gravitational field is negative (which Guth calls a "miracle of physics"). Starting at 0:52:00 in that video clip, Guth presents this thought experiment... ...where it's taken as a given that ...


1

How is KE accumulated and thus increasing? This is my primary concern. Also, what's happening with velocity? Is it increasing? Because if KE is increasing then velocity also should increase, right? Between $x=0$ and $x=x_1$, a net force, say $F$, is acting on the body. With Newton's Second Law we get: $$F=ma,$$ with $a=\frac{dv}{dt}$ the acceleration ...


2

Because of the Work-Energy Theorem. The work done on an object by an external force $\vec{F}$ is $$W=\vec{F}\cdot \Delta \vec{x},$$ where $\Delta \vec{x}$ is the displacement. The Work-Energy theorem says that the work is equal to the change in kinetic energy: $$\Delta K=W.$$ So the reason that the kinetic energy is changing for the particle is that ...


0

The author says, in Cartesian coordinates (denote them $x$, $\dot{x}$), kinetic energy does not depend on the second derivative of the coordinate. This is a general statement about Cartesian coordinates, not any coordinate system. Thus, if $T$ depends on $q$, it is solely because it is, in a sense, non-Cartesian --- i.e., curvilinear. Hence this argument is ...


0

A test particle in general relativity moves along a worldline. If the world line is differentiable, then it has a tangent. If the test particle is similar to a massive particle, that worldline has tangents that are always timelike. And you could make a unit tangent. That unit tangent lives in the 4d tangent space. As does the energy-momentum vector. In ...


0

Let us start with one of the first sentences in Wikipedia "in physics energy is a property of objects which can be transferred to other objects or converted into different forms, but cannot be created or destroyed. The "ability of a system to perform work" is a common description, but it is difficult to give one single comprehensive definition of energy ...


4

There is no such state; energy does not work like that. Energy is not an object, but a property of physical objects. Light (i.e. ripples in the EM field) has energy, as do electrons (excitations of the electron quantum field), but there is no such thing as "pure energy". It's as if you asked the question, "some buildings are very high, and some are short, ...


0

I do not think many people attempt to find the absolute total internal energy of a system. Rather they will pick and choose what needs to be counted to suit their purposes. If interested in statistical mechanics then treated atoms as billiard balls which can rotate and vibrate, have translational kinetic energy and potential energy due to the inter atomic ...


0

The important point is that the first law is an equation considering the total change between two different states . First this process that you describe is a quasistatic one with constant presure and work done by the system changing is volume; second, like the internal energy $\Delta U$, the change of enthalpy $\Delta H$ is a state variable that describe ...


0

The first law of thermodynamics is often confusing, because of the "normal" designation of work being positive if the system is doing work on the environment, and heat transfer being positive if heat is being added to the system. This confusion can be easily fixed, as noted below. All terms in the first law, (e.g., changes in internal energy, heat, and ...


0

The definition of enthalpy $H=U+PV$ can be compared ton a statement of the first law at constant pressure $Q = \Delta U + P\Delta V$ with $\Delta H = Q$. It is not a good idea to use @Q and @W because you cannot have a final amount of heat take away an initial amount of heat and similarly for work done. Just use Q and W for heat into system and work done ...


0

I also had hard time to picture what Feynman wanted to explain. It feels like my confusion arose from lack of proper definitions of system state, perpetual motion, and reversible machine. The examples he used are also not quite clear of the mechanical apparatus used, not sure if by design he wanted to abstract away that from the reader, but if so, I would ...


2

From the moving frame of reference, the rock is moving upward with an initial velocity of 4 m/s, and, at the end of the same time interval, it is moving upward at 1 m/s. But now, as reckoned from the moving frame of reference, the change in potential energy is going to be different. This is because the datum for potential energy is moving downward, so, as ...


1

You are ignoring the change in the kinetic energy of the Earth as it and the rock accelerate towards their common centre of mass. If the rock speeds up in your moving frame then the Earth slows down in the moving frame and you have to consider both changes for the energy to balance. Obviously the change in the Earth's kinetic energy is tiny, but you need to ...


0

The only way that quote makes sense to me is if he assumes his conclusion. He must have written some constraints on the allowed forms of kinetic energy.


1

Note that you are calculating the PARTIAL derivative with respect to $q$, you must consider anything that is not $q$ ( $\dot q $ may implicitly depend on q and t but that doesn't matter when taking the partial derivative with respect to $q$) is just considered a constant, thus its partial derivative vanishes. I can't tell you more, it's just the properties ...


3

Alright - I promised an in-depth answer, so here it is! First: we outline our assumptions. The walls are perfectly well insulated. There is a small heater in the center of the room. This is a one-dimensional room. This greatly simplifies the problem, but the result should be correct within an order of magnitude. Now, we need a way to implement our ...


0

I think there is a problem in your question, cause "sound" is a phenomena in the meaning of process. When we talk about renewable energy, we in fact generally discuss sources (E.g. sun, not EM waves). Straightforward and basically there are two, mostly engineering problems: Sound is a mechanical wave of a very low energy compared to industrial processes ...


5

Sound could be considered a renewable resource if taken from a source that was created by continual physical processes - such as the sound of waves crashing against rocks. Although those sound waves contain energy (which is the kinetic energy of moving/vibrating air particles), their energy density is very low. Therefore they are not useful for generating ...


4

I think you might be a little confused. The phrases 'renewable energy' and 'un-renewable energy' are used to refer to industrial sources of energy. These industrial sources include Wind, Solar, Wave, and Nuclear power, and traditional fossil fuels (coal, oil, natural gas etc.). If a source of power is renewable, it is not depleted (used up) when utilised ...


3

The third plate will be attracted into the gap between the two outer plates so you get work, $E_\text{in}$, as the third plate moves into the gap. Then you have to do work, $E_\text{out}$, to pull the third plate out of the gap again. If the two outer plates stay fixed then the two amounts of work are equal: $$ E_\text{out} = E_\text{in} $$ and energy is ...


0

The reason for the "apparent" confusion, is that you ere, inadvertently, changing the frame of reference! In addition, the formula you are using is not correct for the cases in question. The energy being calculated, is the energy required to make a change in velocity $$E = m(\Delta v)^2 \ were\ \Delta v = v - v_o$$ For the case "walking on ground" $v_o ...


1

Your equation k*exp(-r/a) is the wavefunction(n=1,I=0,m=0), so n=1 = ground state. So while n does not appear explicitly in the equation, it’s really there and it’s equal to 1 in this case. The equation should really be written H x wavefunction(n) = En x wavefunction(n), En = E(0)/n^2.


1

The time required for the wall to attain its steady state temperature profile is going to be on the order of $L^2/\kappa$, where $\kappa$ is the thermal diffusivity of the wall material (averaged over the materials that comprise the wall), and L is the wall thickness. This characteristic time arises as a result of reducing your transient heat conduction ...


1

Yes, it "Is possible to generate energy from gravity". Gravity affects the orbit of the moon. The moon affects the level of tide waters. The movement & mass of tide waters can be captured & converted into electrical energy using energy harvesting technologies. e.g.: https://www.youtube.com/watch?v=7jsOerwz4Z8


0

As per userTLK's comments, there are two ways we harness gravitational potential energy: Hydro systems are systems where water is given gravitational potential energy by being evaporated by the sun's radiant energy. That gravitational potential energy then converts to kinetic energy - the falling of the water - which is then converted to electricity by the ...


-5

Time to brush up on our physics: (1) There are two types of Energy in the Universe: Electromagnetic and Scalar. Scalar waves travel faster than light. (2) A straw does NOT get blown in to a tree during a tornado. There is a warping of space/time within the vortices of tornados. The tree and straw simply occupy the same space but at different times. When ...


0

If the questions says that zero potential energy level is on ground then the answer is zero for total mechanical energy. but in actual the zero potential energy level is at infinity. You will define a different point for Z.P.E.L only while doing a calculation with mechanical energy to do it easily.


2

First of all, you need to be specific of which energy you are looking for. The phrase "the energy" is not specific as people may interpret it in different ways based on their common practices. If you define your zero valued potential energy at the ground, then the mechanical energy is zero. Note that if the mechanical energy is zero, it does not mean that ...



Top 50 recent answers are included