3
votes
3answers
3k views

Where does the energy of a lightning strike go?

Lightning contains a lot of energy, so where does this energy go after lightning has hit the ground? Does it travel all the way to the core? What happens after that?
8
votes
6answers
319 views

Why does hot air raise in a column instead of cold air pressing down?

Ok, this looks like a dumb question or even near trolling, but I really don't understand it. When air is heated over an oven plate, it rises. Obviously, I can check by blowing some smoke in. The ...
-3
votes
1answer
10 views

Could it be possible for man to create a star?

If it were possible for us to create a star or a new sun, how could it be done, or how would it have to be done?
0
votes
1answer
198 views

Dispersion in a rectangular prism

Why are the colours visible only at the fringes of the light refracted through a rectangular prism?
0
votes
0answers
3 views

Dependance of diffusion coefficient on size?

What's the dependance of the diffusion coefficient on size? More explicitly, suppose I have a particles of characteristic length $l$, dissolved in a liquid. How does $D$, the diffusion coefficient of ...
0
votes
0answers
9 views

Acceleration of an bubble under the sea

An air bubble arises from the bottom of the sea. Find its acceleration if resistance force is proportional to $\rho Av$ where $\rho$ is density of water, $A$ is cross section area and $v$ is velocity ...
0
votes
2answers
13 views

volume of the air bubble in the water

How does the depth affect the volume (the radius) of an air bubble in the water, if the temperature and density of the water are constant. Is there any relation combining this?
0
votes
1answer
17 views

Navier Stokes : what about angular momentum?

I play with CFD for a while, and suddenly, a transcendantal question raises: :-) Navier Stokes is basically Newton applied on a continuum in Eulerian. For solids, we would consider linear, but also ...
0
votes
0answers
9 views

photometric redshifts - the origin of 1 / (1+ zspec) in photometric accuracy

i have a training sample of sources with known spectroscopic redshifts ($z_{\rm spec}$) and i run a photometric fitting code that uses a template to determine the photometric redshifts ($z_{\rm ...
1
vote
1answer
157 views

Rotation motion like the number 8

I'm a college student majoring in culinology and I'm trying to find out the reason or method of the number 8 motion. Responses doesn't have to be in culinology examples, but that would be a great help ...
1
vote
1answer
21 views

Density parameter (cosmology) as a function of redshift

Hopefully I'm missing some very basic algebra for this question. In essence, I need to derive the following: $$ \Omega=\Omega_{1}\frac{(1+z)}{1+\Omega_1{z}} $$ Now, I proceeded from the Friedmann ...
0
votes
2answers
24 views

How can space strech a wave?

Because of the expanding of the universe a wave from a far galaxy or star can be streched to more red. But how is space doing that? There must be a kind of 'entanglement' between the wave and space. ...
0
votes
1answer
23 views

Is the energy of a collision of two photons the same as one photon hitting a 'wall'?

Special relativity says that the speed of ligt is always the same. So when a photon meets another photon he will encouter it with the speed of light and also the other one. But in case of a wall, the ...
1
vote
2answers
172 views

Thought Experiment: Force on magnets in a Stern Gerlach Experiment

Background: In the SG experiment, an inhomogenous magnetic field affects a force on particles passing between two magnets. "Measurement" takes place when a screen is placed on one end, blocking one ...
0
votes
2answers
249 views

A lever arm-definition question

My question is regarding Torque, and specifically the definition of the lever arm. As far as I've understood, the lever arm is the line perpendicular to the line of action to your reference point. ...
-4
votes
0answers
12 views

The following model describes a jet travelling at 40000 ft at Mach 8. My question is: where do these numbers c0me from?

This model describes flight of an aircraft at 40,000 ft at a speed of Mach 0.8. x˙ = Ax + Bu Matrix A = [-0.0558 -0.9968 0.0802 0.0415 0.598 -0.115 -0.0318 0 -3.05 0.388 ...
-2
votes
0answers
21 views

Motion question [on hold]

I have been struggling to understand how to do this question so some guidance would be great. A racing car of mass 941kg accelerates from 28km/h to 102km/h over a distance of 297m. Frictional forces ...
1
vote
0answers
17 views

Does a potential of interaction produce also torque?

I have a system of particles (spheres with masses and radii), with $6$ degree of freedom (they are free to move and rotate as they wish). Between each couple there is an interaction potential $V(d)$, ...
0
votes
1answer
242 views

Proof of Ampère's law from the Biot-Savart law for tridimensional current distributions

Let us assume the validity of the Biot-Savart law for a tridimensional distribution of current:$$\mathbf{B}(\mathbf{x})=\frac{\mu_0}{4\pi}\int_V ...
3
votes
4answers
257 views

What will be final velocity of three charges $q$, $q$, $2q$? [on hold]

What will be final velocity of three charges q, q and 2q kept along an eqilateral triangle of side r at infinite distance. All three masses are equal. I tried to conserve Total Energy ...
0
votes
0answers
27 views

Integrating the geodesic equation to obtain Newtonian energy of test particle

I am studying General Relativity, and have come across a question that I am finding rather intractable: In Newtonian Theory, the energy equation for a test particle in orbit around a point mass ...
-1
votes
0answers
13 views

How to find frequency from wave equation [on hold]

I have wave equation for vibrating string with damping $M\ddot{x}+C\dot{x}+Kx=0.$ I used this formulae for finding (natural)frequency $\sqrt{\frac{K}{M}-(\frac{C}{2M})^2},$ is it ok?
-1
votes
2answers
24 views

What is the expression of the state after $n$ parallel hadamard gate on $n$ $\left|1\right>$ qubits?

The state after $n$ parallel hadamard gate on $n$ $\left|0\right>$ qubits is $\frac{1}{\sqrt{2^n}}\sum_{x}\left|x\right>$. I am looking for a similar expression for $n$ $\left|1\right>$ ...
1
vote
0answers
13 views

solar energy on a specific location

How to find the amount of solar wattage in any specific place on earh in a monthly manner? by solar wattage I mean the energy recieved from the sun in a squared meters.
1
vote
1answer
19 views

What does ''population'' mean in regards to the excited and ground states of an atom?

I have a problem I'm working on. It seems simple enough, but there is a term I'm not familiar with. It asks for the ''relative populations of the first excited and the ground states for helium gas in ...
4
votes
1answer
51 views

Meaning of integral signs in classical physics

When I began studying physics, by myself, on a universitary textbook, F.J. Keller, W.E. Gettys , M.J. Skove, Physics, about one year ago, I believed that all the integrals that I was going to find in ...
-6
votes
1answer
29 views

Simple harmonic oscillators

A block whose mass m is 680g is fastened to a spring whose constant k is 65N/m . The block is pulled a distnce x=11cm from its equilibrium postion at x=0cm on a frictionless surface and released ...
-2
votes
1answer
58 views

Why is particle superposition still part of quantum mechanics?

After reading an article on Schrodinger's Cat, it seems that if we take the environment as an observer, that superposition cannot occur because all atomic and subatomic entities would be observed all ...
1
vote
1answer
13 views

Applicable force at constant velocity

For a body moving at a constant velocity, the force $F_{net}=ma$ Since acceleration is 0, $F_{net}=0$ (i.e force applied = resisting force) Since force applied and resisting force are equal, will ...
1
vote
0answers
11 views

Energy and power in a travelling sinusoidal wave

This stuff is driving me crazy. Here: http://galileo.phys.virginia.edu/classes/152.mf1i.spring02/AnalyzingWaves.htm I found that the average kinetic energy per unit length is: $$ \frac{1}{4}\mu ...
15
votes
9answers
8k views

Why is it possible to drive a nail into a piece of wood with a hammer, but it is not possible to push a nail in by hand?

It is possible to drive a nail into a piece of wood with a hammer, but it is not possible to push a nail in by hand. Why is this so?
-1
votes
0answers
13 views

Problem in statics [on hold]

This is a problem I've been trying to solve for the past days without success. I tried the mathematics forum, since the whole problem consists in finding the value $\beta$ which produces a maximum $P$ ...
1
vote
2answers
97 views

What general relativity predicts in such a situation?

If there's a system of a point mass or point particle with mass 'm' and a structure such that - The structure is made of many concentric spheres (shells) with certain thickness and the radius of those ...
2
votes
1answer
18 views

What information does kinetic energy and work give us about a body?

When I studied momentum I learned that momentum says about a body how hard is it to stop it. In addition, I learned that impulse tells us in some way how much time would I need to stop the object. If ...
2
votes
1answer
42 views

How is LIGO so sensitive? [duplicate]

My understanding is that interferometers can detect distance changes on the order of the wavelength of light being used. LIGO uses 808 nm light but has a sensitivity of 10^-18 m. Where do those 11 ...
1
vote
2answers
81 views

How does magnetism work? (Not asking what magnetism does)

To clarify, if I asked "how does electricity work" I would want "electrons flow from a negatively charged area to a positively charged area", not "it powers electronics like phones" as an answer. The ...
0
votes
0answers
11 views

complex waveforms

just wondering if anyone can help me out with a expression I need to find out the phase angle of any hardmonic components present ( relative to the fundamental) of this expression v= 100SIN (100 V = ...
4
votes
1answer
293 views

Quantum Hall Effect and Edge States

In quantum hall effect we measure the hall conductance (in transverse direction) which is quantized. My question how do they take care of the edge states that are in the longitudinal side?
2
votes
4answers
2k views

Total angular momentum of deuteron

I'm studying for my nuclear physics exam and the book we use is Introductory Nuclear Physics by K.S. Krane. In the chapter on Basic Nuclear Structure, we research the deuteron. However, when ...
0
votes
1answer
45 views

Is there any description of a mechanism of curving of space-time fabric

Most of us know about famous line - "mass tells space how to curve and space tells mass how to move". There is quantitative description of the curving and its effects in Einstein's theory. Mass and ...
1
vote
0answers
45 views

Does an expectation value over only part of a wavefunction have physical meaning?

Does the expression: $$\langle p\rangle_{x=a, b} =\frac{\int_a^b \Psi(x)^*\,\hat{p}\,\Psi(x)dx}{\int_a^b |\Psi(x)|^2dx} $$ have any physical meaning when $\int_a^b ...
-2
votes
1answer
30 views

how to calculate the angular velocity of ball from hitting angle?

i want to know how to figure out the angular velocity of ball in 2D when it's hit at a different known angles and constant force ? like in image ,and sorry if i had missed an info.
0
votes
0answers
7 views

How to calculate apex angle of sun shining on the Earth

I'm trying to compare the brightness of various LEDs to the average brightness of natural daylight. LEDs are rated in terms of candelas whereas the Sun is measured in terms of lumens, so I need to ...
1
vote
0answers
7 views

Is the magnetic dipole moment in charged particles the more survivable property than the electric charge?

After asking about Which of the properties of particles are intrinsic properties and why? it was commented "Charge, spin, lepton number, baryon number definitely. Mass maybe." and "is magnetic dipole ...
1
vote
0answers
25 views

Extrinsic Curvature of Surface of Codimension > 1

We can define the extrinsic curvature of a codimension-one surface as $$K_{ab} = q_a^{\phantom{a}c} q_b^{\phantom{b}d} \nabla_c n_d,$$ where $n^d$ is the normal vector to the hypersurface and ...
0
votes
1answer
14 views

What would the (simplified) formula for the gravity assist look like if mass were introduced as one of the variables?

The (simplified for laymen) formula for calculating the velocity a probe would gain via the flyby of a planet is: The Resulting Velocity of the Probe Relative to the Sun = v + 2U ... where v is ...
0
votes
0answers
15 views

Electric Filed on a point on a sphere

I really want to understand the concept of those problems. Thanks.
10
votes
1answer
310 views

How to understand topological order at finite temperature?

I have heard that in 2+1D, there are no topological order in finite temperature. Topological entanglement entropy $\gamma$ is zero except in zero temperature. However, we still observe some features ...
0
votes
0answers
19 views

Reattachment of differential equation in Physics

The following differential equation: $$xf'(x) + f(x) = 2x$$ Has solutions on the intervals $]-∞;0[$ and $]0;+∞[$ : $$f(x) = x + a/x$$ $$f(x) = x + b/x$$ I obtained the only common to the two ...
0
votes
0answers
13 views

How does back reflection damage optical cavity?

I have a basic question.How does back reflection damage optical cavity?please help me.

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