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56675 | What fraction of peak horsepower do typical 4 door passenger vehicles use? | I was surprised when I looked at the power rating of the engine used on a Humvee. It's only ~190 horsepower, which is exceeded by many sedan engines. So an obvious question is why doesn't my Camry SE burn more gas than a Humvee and I think it's just because during regular use, it doesn't use anywhere near 250 HP. Does ... | What is the typical mechanical power output of a sedan engine during highway driving, and how does this compare to the horsepower used by a Humvee engine in similar driving conditions? Additionally, what can be inferred about the torque vs. RPM characteristics of both engines at typical operating points? | 28,092 | cqadupstack-physics |
57493 | Why coercivity increase in after depositing organic on top of Ferromagnet | I had deposited Fullerene on top of Cobalt thin film which result in increase of coercivity. | What is the relationship between the deposition of Fullerene on a Cobalt thin film and the observed increase in coercivity, and how might this affect the magnetic properties of the resulting material? | 6,503 | cqadupstack-physics |
95696 | Is this explanation for the no-slip condition at a pipe wall correct? | The standard boundary condition for a fluid in contact with a surface is to enforce matching velocities at the interface. The explanation I was given is that contact forces between the wall and the fluid particles drag the velocity down to zero. As I understand it, the key point is that fluid particles that are desorbi... | Can you explain why the velocity of fluid particles at a solid boundary is considered to be zero? What role do contact forces and viscous momentum transport play in this behavior? | 26,000 | cqadupstack-physics |
52511 | Any suggestions for units conversion? | > **Possible Duplicate:** > Photometer: measured Irradiance L converted to photon rate I am conducting a experiment where stimulus output of $470\ nm$ is measured by a radiometer at $30\ \mu W\ cm^{-2}$. The stimulus is $1$ inch from the detector. Any suggestion on how I might go about converting $\mu W\ cm^{-2}$ to... | How can I convert a stimulus irradiance of \(30\ \mu W\ cm^{-2}\) at a wavelength of \(470\ nm\) into log photon flux in units of \(cm^{-2} s^{-1}\)? | 17,807 | cqadupstack-physics |
129382 | Why does the speed of the Electromagnetic wave in the material depend on the frequency of the wave where as they are constant in vacuum (freespace)? | I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM waves in other materials depends on the frequency? Can someone give me a good proof of this phenomena with appropriate ... | Why do electromagnetic waves propagate at a constant speed of approximately \(3 \times 10^8\) m/s in a vacuum, while their speed varies in different materials depending on their frequency? Can you provide a mathematical explanation, including relevant formulas related to the refractive index? | 12,481 | cqadupstack-physics |
13943 | How does the period of a temperature fluctuation affect the depth to which the ground freezes? | On account of the annual fluctuation of temperature the ground at the town of Ν freezes to a depth of 2 metres. To what depth would it freeze on account of a daily fluctuation of the same amplitude? Found this on aops while gazing through some questions (So that people dont blame me for posting a phy q on math site). A... | If the ground in town N freezes to a depth of 2 meters due to annual temperature fluctuations, what would be the expected freeze depth if the temperature fluctuates daily with the same amplitude? | 12,519 | cqadupstack-physics |
43696 | Will ideal gas law apply to plasma? | I have read that plasma is a state of matter that resembles gas but it consists of ions and electrons coexisting. So my question is : If plasma is just ionized gas, will ideal gas law apply for it ? | Can the ideal gas law be applied to a plasma consisting of ions and electrons, and if so, under what conditions would it be valid? | 7,733 | cqadupstack-physics |
25397 | Is there any site/place which gives access to astronomical signals acquired from space? | I am an engineer and I'd like to know if there are any places which provide access to any kind of astronomical signals acquired from space using radio telescopes. | What are the key facilities worldwide where researchers can access astronomical signals obtained through radio telescopes, and what types of data do they typically provide? | 13,795 | cqadupstack-physics |
109167 | Faraday's law and "infinite induction" | I may have confused after thinking too much about Faraday's law. If an emf is induced in a circuit due to some changing magnetic field, the induced current will be in a direction such that the "induced magnetic field" opposes the original magnetic field (Lenz's law). So wouldn't the induced magnetic field also generate... | How does Lenz's law ensure that the induced current and magnetic field do not lead to an infinite series of induced fields and currents when a sinusoidal magnetic field is applied? Can you provide a mathematical explanation or example? | 27,235 | cqadupstack-physics |
66621 | Hamiltonian equations: can I divide a solution of motion for a constant? | I'm solving an exercise about Hamiltonian equations. I have followed the proceeding below. The results given by the book are different to mine because its first result is the half of mine (and the second one linked to the first one is different to mine). I think that my proceeding is correct and so I can't understand..... | Given the Hamiltonian equations:
$$\dot p = -\alpha pq,$$
$$\dot q = \frac{1}{2} \alpha q^2,$$
with initial conditions \( p(0) = p_0 \) and \( q(0) = q_0 \), derive the expressions for \( q(t) \) and \( p(t) \) and show that the solutions can be expressed in the forms:
$$ q(t) = \frac{q_0}{1 - \frac{1}{2} \alpha... | 37,792 | cqadupstack-physics |
43049 | Inelastic Scattering and coherent scatterng | Another Scattering Question So I have this Bravais Lattice of sites R vibrating with some normal mode with a small displacement amplitude $u_o$, some wave vector k and some frequency $\omega$. We can clearly describe $u(R)=u_o \cos(k R - \omega t)$. If we scatter a beam of radiation from the lattice with a change of wa... | What conditions on the wave vector \( q \) must be satisfied for coherent scattering in a Bravais lattice, considering the lattice vibrations described by the displacement amplitude \( u_o \) and the given wave vector \( k \)? Specifically, how can we determine the set of wave vectors \( q \) that lead to constructive ... | 15,941 | cqadupstack-physics |
53889 | Do residents of the Hudson Bay area have more time? | Apparently there is a gravity anomaly in the Hudson Bay Area in Canada: gravity is "missing" or it is slightly less than it is in the rest of the world. Does that mean that things in the Hudson Bay Area would theoretically be at a higher gravitational potential, and consequently clocks would run faster there? Would peo... | How does the lower gravity in the Hudson Bay Area affect the gravitational potential, and what is the theoretical difference in the time experienced by people living there compared to those in other regions, quantified in nanoseconds over a lifetime? | 4,142 | cqadupstack-physics |
110489 | Capillary in a slanted tube with a bend | So I've read a question on here about Capillary action in a slanted tube, but my question goes a little further. Firstly though, could someone explain to me what is meant by the only answer to that question. The answer states that the lift force isn't dependant on the weight of the fluid whereas the capillary lift high... | In a tube that slants 15 degrees to the right for 10 mm and then 15 degrees to the left for another 10 mm, what is the theoretical capillary rise height compared to a straight tube that is 20 mm long, assuming both tubes have the same radius? Additionally, how does the angle of the slant affect the effective capillary ... | 35,590 | cqadupstack-physics |
113784 | Integration of Dirac propagator | I've got confused with Dirac (or Spinor) Propagator. Everywhere in books I have examples of integration Klein-Gordon propagators, which are quite easy. But I don't understand how to integrate 4-component function. My second question - how to deal with a mix of Dirac and KG propagators in one equation? I know that if we... | How can the integral involving the Dirac and Klein-Gordon propagators expressed as $$S_a(x_1-x) D(x-y) S_b(x-y) S_a(y-z) S_b(z-y_1) D(z-y_2)$$ be evaluated in the context of a particle decay process, specifically when \(a\)-fermion decays into \(b\)-fermion and scalar particles, given the interaction Hamiltonian \(\mat... | 15,090 | cqadupstack-physics |
9113 | How sound intensity (dB) and sound pressure level (dB) are related? | Source: http://www.engineeringtoolbox.com/sound-power-intensity-pressure- d_57.html Both sound intesity and pressure level are measured in dB. Given a specific sound, are these two dB values the same? | If a sound has a measured sound intensity level of 90 dB, what would be its corresponding sound pressure level in dB? Assume the ambient pressure is 20 µPa. | 8,584 | cqadupstack-physics |
52411 | Why can I add the Atomic form factors in the calculation of the Diamond Structure factor | When trying to calculate the structur factor for diamond I came across the calculation on the wikipedia. In the calculation they just add up the atomic form factors of alle the atoms in the unit cell to calculate the structure factor. However I thought, that the Atomic structure factor is the Fouriertranform of the ele... | How does the rotation of atomic electron distributions in the diamond lattice affect the calculation of the structure factor, and can you calculate the structure factor for diamond considering the contributions from both types of atoms in the unit cell? | 1,988 | cqadupstack-physics |
5676 | Questions on string theory vacuum and quantizing gravity | Actually I have few questions. The answer to a question related to string field theory helped me, but let me still ask it as its probably a bit different. When e.g we do bosonic/super string theory we see that the vacuum is $|o,p>$ that is not a true space time vacuua (I mean a unique |0>) (depends on CM momenta of str... | In the context of string theory, is it possible to derive a unique translationally invariant space-time vacuum state analogous to that in quantum field theory (QFT), given that strings do not annihilate in the same way as particles? What are the implications of this for our understanding of quantizing gravity in string... | 1,303 | cqadupstack-physics |
97941 | Compare Dynamics of Cosmic Ray Neutron Radiation | Examining cosmic ray neutron radiation near ground by neutron monitors for example (http://www.nmdb.eu), different stations show similar dynamics in the signal. At one station, I like to "substract" the incoming radiation in order to obtain information about local effects. Can I take the incoming signal from another st... | How can I analytically correct for differences in signal amplitude, time lag, and detector efficiency when comparing cosmic ray neutron radiation data from different monitoring stations? | 29,064 | cqadupstack-physics |
80247 | Why 3 dipole terms in a multipole expansion? | As can be seen on this page http://en.wikipedia.org/wiki/Multipole_expansion when we take a multipole expansion _without_ assuming azimuthal symmetry we end up with $2l+1$ coefficients for the $l^{th}$ moment in the expansion. So the dipole moment has 3 terms, the quadrupole has 5 and so on. This is different to the ca... | In a multipole expansion without assuming azimuthal symmetry, each moment \( l \) requires \( 2l+1 \) coefficients. Can you explain why the dipole moment, which has \( l = 1 \), has 3 coefficients, and how these correspond to the three Cartesian axes? Additionally, how are the coefficients interpreted for higher order ... | 27,925 | cqadupstack-physics |
86781 | How bright was the AGN eruption at the center of the Milky Way ~2 Ma ago? | The black hole at the center of the Milky Way is believed to have erupted as an active galactic nucleus (AGN) approximately 2 million years ago, at which time it would have been visible to early humans. How visibly bright would such an eruption have been, and how sudden would its onset have been? | If the black hole at the center of the Milky Way erupted as an active galactic nucleus (AGN) 2 million years ago, what would the apparent magnitude of this eruption have been as seen from Earth, and how long would it have taken for the brightness to reach its maximum level? | 2,734 | cqadupstack-physics |
121629 | Why don't we consider electrostatic energy of the pair in the case of pair production? | I have seen this Wikipedia article and many others, but in none of them I find any mention of the **electro-static energy** of the generated pair. Why? I mean, the energy conservation should be written as $h\nu = E_+ + E_- + Electrostatic\ Energy$ | In the context of particle pair production, if a photon with energy \( h\nu \) creates an electron-positron pair, calculate the electrostatic energy of the pair when the particles are separated by a distance \( r \). Assume the charges of the electron and positron are equal in magnitude but opposite in sign, and use Co... | 24,305 | cqadupstack-physics |
2425 | Why is the equivalence principle so important to general relativity? | In its simplest form, equivalence principle states that the inertial mass and the gravitational mass should be the same. This is easy to understand. But why is it so important to the formulation of General Relativity? To be more specific, I don't understand how the gravitational field equation: _{z}\left( \frac{\partial y}{\partial z} \right)_{x}\left( \frac{\partial z}{\partial x} \right)_{y}=-1$$ State the properties that must be $x=x(y,z)$, $y=y(x,z)$, $z=(x,y)$. The truth is I do not know how to start, an... | Can you derive the identity $$\left( \frac{\partial x}{\partial y} \right)_{z}\left( \frac{\partial y}{\partial z} \right)_{x}\left( \frac{\partial z}{\partial x} \right)_{y}=-1$$ and explain the necessary conditions for the functions $x = x(y, z)$, $y = y(x, z)$, and $z = z(x, y)$ that allow it to hold true? | 18,489 | cqadupstack-physics |
130666 | How can I apply to the differential form of Gauss' Law? | I'm trying to learn Maxwell's equations but I got stuck. I couldn't understand the usage of the differential form of the Gauss' law. How can it be applied to questions? For example, let's say there is a plate sizes of 10 cm X 5 cm and has a charge of 1 C. To calculate the electric field on the point **_a_** , can I use... | How can I use Gauss's law in differential form (∇⋅E = ρ/ϵ0) to calculate the electric field at a point **_a_** located 1 cm away from a uniformly charged plate measuring 10 cm by 5 cm with a total charge of 1 C? | 14,711 | cqadupstack-physics |
72280 | ${f=ma}$: a duality between F-theory and M-theory? | $$F = M \Big|_{A(T^2) \to 0}$$ The above equation is the duality equation between F-theory and M-Theory on a vanishing 2-torus. What's the explanation for this equation? Is there anything similar to this equation with M-theory and type IIB theory, and how can ones explain it? | What implications does the equation $$F = M \Big|_{A(T^2) \to 0}$$ have on the relationship between F-theory and M-theory when the 2-torus vanishes, and how does this compare to the relationship between M-theory and Type IIB string theory? Provide a detailed explanation. | 5,718 | cqadupstack-physics |
99888 | How do I calculate pressure drop across a reduction in pipe diameter? | If reducing from one pipe size to another through a reducing fitting, say 6.25cm to 5cm, how do I calculate the pressure drop? Also, how does this impact a change in volumetric flow rate (or does it affect the volumetric flow rate)? | Given a fluid flowing through a pipe that reduces from a diameter of 6.25 cm to 5 cm, calculate the pressure drop if the volumetric flow rate is 200 liters per minute. Additionally, determine how this change in pipe size affects the volumetric flow rate, assuming incompressible flow. | 9,443 | cqadupstack-physics |
5194 | How is the speed of light calculated? | How is the speed of light calculated? My knowledge of physics is limited to how much I studied till high school. One way that comes to my mind is: if we throw light from one point to another (of known distance) and measure the time taken, we could know the speed of light. but do we have such a precise time measuring to... | If a laser beam travels a distance of 300,000 kilometers and takes 1 second to cover that distance, what is the speed of light in kilometers per second? | 19,281 | cqadupstack-physics |
93471 | Difference: Fermi wave length vs. phase-breaking length? | I am reading a quantum transport book, where they often mention: phase breaking length and Fermi wavelength. I have looked up and found that: **Phase breaking length** = length over which electron remains its phase. **Fermi wavelength** = Wavelength associated with the maximum energy of electron (Fermi energy). This is... | What is the relationship between the phase-breaking length and the Fermi wavelength in a metal, and how do they influence electron transport in different conduction regimes? | 21,984 | cqadupstack-physics |
38735 | Mathematics for Quantum Mechanics | What math should I study if I want to get a basic understanding of quantum mechanics and especially to be able to use the Schrodinger's equation. | What are the minimum requirements for mathematical knowledge, such as specific topics or areas of study, needed to effectively understand and apply the Schrödinger equation in quantum mechanics? | 17,687 | cqadupstack-physics |
115094 | Standing sound waves phase difference | This is a basic question but I don't fully understand what is going on. When we have a pipe in resonance we get standing waves, where displacement antinodes are at pressure nodes and vise versa. So we have a situation where pressure and displacement are 90 degrees out of phase, this means you can differentiate the disp... | In a pipe that is resonating with a fundamental frequency of 440 Hz, the length of the pipe is 1 meter and it supports a standing wave. If the speed of sound in air is approximately 343 m/s, what is the wavelength of the sound wave in the pipe, and how does this relate to the observed phase difference of 90 degrees bet... | 134 | cqadupstack-physics |
112961 | Manipulation with braket notation | I am still getting used to the braket notation. Is this manipulation correct? $$ \frac{-\hbar^2}{2m}\int_{-\infty}^{\infty}\frac{\partial^2\phi_n^*}{\partial z^2} \phi\,dz = \int_{-\infty}^{\infty}\phi\left(\frac{-\hbar^2}{2m} \frac{\partial^2}{\partial z^2}\right)\phi_n^*\,dz = \int_{-\infty}^{\infty} \phi \hat{K}\phi... | Verify the correctness of the following manipulation involving braket notation and the operator \(\hat{K} = \frac{-\hbar^2}{2m} \frac{\partial^2}{\partial z^2}\):
$$ \langle \phi | \hat{K} | \phi_n \rangle^* \stackrel{?}{=} \int_{-\infty}^{\infty} \phi^* \hat{K} \phi_n \, dz $$
What is the physical significance of ... | 20,581 | cqadupstack-physics |
103105 | Breatheability of atmosphere above 3000 meters | I would like to offer you a slight correction on your statement that 3000 m is about the limit of breathable atmosphere. Unless I misunderstood you, I need to point out that many people live in Leadville Colorado above 3000 m and it's really quite comfortable unless you are from a sea level altitude and have not had th... | What physiological adaptations occur in the human body at high altitudes, specifically regarding hemoglobin levels, and how do these adaptations facilitate acclimatization for individuals living above 3000 m? | 23,760 | cqadupstack-physics |
29367 | Why is there a phase factor when the two composite angular momentum is exchanged in Clebsch–Gordan coefficients | An identity exists for CG coefficients: $$\langle j_1 m_1 j_2 m_2 |J M \rangle = (-1)^{j_1+j_2-J} \langle j_2 m_2 j_1 m_1|J M\rangle,$$ But why is there a phase factor $(-1)^{j_1+j_2-J}$? It seems to me that $$|JM\rangle =\sum_{m_{1},m_{2}}|j_{1}m_{1}\rangle\otimes|j_{2}m_{2}\rangle\langle j_{1}m_{1}j_{2}m_{2}|JM\rangl... | In quantum mechanics, the Clebsch-Gordan coefficients include a phase factor expressed as $$(-1)^{j_1+j_2-J}.$$ Can you explain the significance of this phase factor and how it affects the normalization of the states when combining angular momenta, specifically for the cases where $j_1$, $j_2$, and $J$ take half-intege... | 16,864 | cqadupstack-physics |
18193 | Theoretical proof forbidding Loschmidt reversal? | In a famous debate, Loschmidt criticized Boltzmann's new theory of statistical mechanics by asking what would happen if the velocities of all the atoms were reversed. Typical objections are that such a reversal would not be possible without a fine detailed control over all the atoms of the system. However, spin echo ex... | What is the probability of successfully reversing the velocities of all atoms in a totally isolated system without detailed control over most of the atoms, and how can this probability be theoretically quantified? | 32,787 | cqadupstack-physics |
32437 | Degeneracy of Energy Levels for 2 identical particles in a One Dimensional box | i am studying for a physics exam and came across an exercise i cannot seem to crack. I have read through Feynmans lecture books & a lot of the internet but i am somewhat stuck. first the question, and then what i have got so far: (Note the problem is originally in German, I hope my translation does not change the probl... | In a one-dimensional box of width 2a with infinite potential energy at the boundaries, consider a system of two identical fermions with spin 1/2. Given that the energy levels for a single particle are defined by \( E_n = \frac{n^2h^2}{32ma^2} \), where \( n \) corresponds to the quantum state of the particle, calculate... | 2,490 | cqadupstack-physics |
18498 | Are proton, antiproton, electron, positron the only observed subatomic particles that can freely exist and don't decay, i.e. are stable? | Are proton, antiproton, electron, positron the only subatomic particles that can freely exist (i.e. I don't want particles that only exist in bound state as constituents such as quarks) and don't decay, i.e. are stable? What about muons? Are there other particles/hadrons that can exist freely (i.e. not in some bound st... | List all known subatomic particles that can exist freely and do not decay, and specify their stability status, including whether they are stable or unstable, with the exception of bound state particles like quarks. | 33,682 | cqadupstack-physics |
105349 | How exactly is the Poisson bracket of the modes of a classical string defined? | In the theory of a classical bosonic string, we have expressions like: $$ \\{\alpha^\mu_m,\alpha^\nu_n \\} = - i m \delta_{m,-n} \eta^{\mu \nu} $$ were $\alpha^\mu_n$ are the Fourier modes of the string. How is this Poisson bracket defined? The definition from analytical mechanics involves partial derivatives with resp... | How can the Poisson bracket for the Fourier modes of a classical bosonic string be defined if the modes \( \alpha^\mu_n \) are treated as constants, resulting in zero partial derivatives with respect to the generalized coordinates and momenta? | 18,496 | cqadupstack-physics |
19420 | What means: distortion <XX% in lens spec? | I'm going to buy a lens and I would like to understand what means "distortion < XX%"? It's a vari-focal 10-60mm lens and mentionned distortion <12-1%. According to my understanding @ 10mm focal the distortion will reach 12% and 1% @ 60mm. Is that right? How do they calculate this per cent?  affect the overall resonance frequency? | 14,958 | cqadupstack-physics |
88430 | Emission and absorption spectra of sun | I heard in a documentary that the elements of the sun can be read out from the absorption lines. But I have also heard that an elements absorption lines and emission lies coincide. That means the sun can emit only the colors that its elements absorb. So if that is the case where does all the other colors (which are not... | If the absorption lines of elements in the sun's atmosphere correspond to specific wavelengths of light that those elements can absorb, how can we explain the continuous spectrum of sunlight we observe, which includes colors not represented in the absorption spectra of those elements? What process allows these addition... | 29,963 | cqadupstack-physics |
101002 | Can you replace the backlight of a thin film transistor (TFT) with a mirror? | I basically know how TFT' displays work. They have on both sides a polarizing foil, in 90 degrees with the crystals in the middle modifying which light particles should pass through or not. The light is emitted by a backlight in the display. So far so good. What I try to find out or understand is, whether it would be p... | Is it theoretically possible to design a TFT display that utilizes a mirror instead of a backlight, allowing polarized light to enter from the front and be reflected back through the display? If so, what modifications would be necessary to the polarizing foils or the liquid crystal layer to make this setup functional? | 15,478 | cqadupstack-physics |
134588 | Demostrating possible equivalence of two tensors | Is there anyway to see by inspection that a form like $$a(x^2 )^{-3} (g _{μσ} x_{\rho} x_{ ν} + g_{μρ} x_{σ} x_{ ν} +g_{νσ} x_{ρ} x_{ μ} + g_{ νρ} x_{ σ} x_{ μ} ) $$ may be equivalent to (i.e reduced down to or reexpressed) $$ b(g _{μν} x_{ ρ} x_{ σ} + g_{ ρσ} x_{ μ} x_{ ν} )(x^2 )^{ −3} ?$$ where $g_{\mu \nu}$ is the ... | Given the two forms \( a(x^2)^{-3} (g_{\mu\sigma} x_{\rho} x_{\nu} + g_{\mu\rho} x_{\sigma} x_{\nu} + g_{\nu\sigma} x_{\rho} x_{\mu} + g_{\nu\rho} x_{\sigma} x_{\mu}) \) and \( b(g_{\mu\nu} x_{\rho} x_{\sigma} + g_{\rho\sigma} x_{\mu} x_{\nu})(x^2)^{-3} \), under what conditions on the coefficients \( a \) and \( b \) ... | 22,934 | cqadupstack-physics |
36486 | What is the difference between infrared heat and "regular" heat? | In Feynman's terms temperature is the speed at which atoms are 'jiggling'. Now, let's suppose I've just eaten a sizable dinner, and my body temperature just got a tad up. Am I emitting more photons in the infrared spectrum, or are my atoms 'jiggling' faster and bouncing more of the air component atoms (nitrogen, oxygen... | What is the relationship between temperature, the jiggling of atoms, and the emission of infrared photons, and how does this relate to the heat we feel from different sources, such as the Sun or a yellow car? Specifically, why is heat transfer commonly associated with the infrared spectrum despite visible light having ... | 20,474 | cqadupstack-physics |
56733 | is there an error in this paper ¿¿ | http://vixra.org/pdf/0908.0079v1.pdf see equation (2.21) the reasoning to get this (2.21) goes from page 9 to page 14 should be the inverse of the potential denoted by $ x(V) $ proportional to the half-derivative ? i mean something $$ x(V)= C\frac{d^{1/2}}{dV^{1/2}}N(V) $$ instead of the author's claim $$ X(V)= A\frac{... | If \( N(V) \) is a function representing a physical quantity dependent on the potential \( V \), and the relationship given by the author is \( X(V) = A \frac{dN(V)}{dV} \), how can we mathematically verify if the proposed alternative relationship \( x(V) = C \frac{d^{1/2}}{dV^{1/2}} N(V) \) is valid, particularly in t... | 1,096 | cqadupstack-physics |
24835 | Scale invariance and self organized criticality | On wikipedia i have found this statement: > In physics, self-organized criticality (SOC) is a property of (classes of) > dynamical systems which have a critical point as an attractor. Their > macroscopic behaviour thus displays the spatial and/or temporal scale- > invariance characteristic of the critical point of a ph... | What are the defining characteristics of a critical point in a statistical system, and how does scale invariance manifest in the behavior of systems at this critical point? | 24,718 | cqadupstack-physics |
89355 | A simple derivation | During the study of a paper I see that its author defines $$\frac{dh^{ab}}{d\tau}:=h^{am}h^{bn}\frac{dh_{mn}}{d\tau}$$ and from this concludes that $$\frac{d}{d\tau}(h^{ab})=\frac{d}{d\tau}(h^{am}h^{bn}h_{mn})=-\frac{dh^{ab}}{d\tau}$$ where $h_{ab}$ is a Riemannian metric that depends on the parameter $\tau$. I Can not... | Given that \( h_{ab} \) is a Riemannian metric that depends on the parameter \( \tau \), and the definition of the derivative \( \frac{dh^{ab}}{d\tau} = h^{am}h^{bn}\frac{dh_{mn}}{d\tau} \), how can you show that \( \frac{d}{d\tau}(h^{ab}) = -\frac{dh^{ab}}{d\tau} \)? What are the steps involved in deriving this equati... | 19,896 | cqadupstack-physics |
59293 | Water excitation with sine waves | I saw that video when they connected a water hose to a speaker emitting 24 hz sine wave, and its _illusion_ on the shape of the follow going out of the hose (because the video capture rate is fixed at 24 fps) I wonder if I can obtain similar effects with much lower frequencies i.e. (8-10 hz) and if possible what can I ... | What is the relationship between the frequency of a sine wave and the visual effects produced when using a water hose to create standing waves, and can you design an experiment to observe similar visual effects at frequencies between 8 and 10 Hz using a water source and a speaker? | 30,857 | cqadupstack-physics |
104263 | A small object on the opposite side of the earth's orbit with 0 velocity,"in line" with the core - would it collide with the earth? | If a small object (say mass 1 kg), at the opposite side of the earth's orbit (six months away), was placed in the same orbital position as the earth's core, at zero velocity in all directions, would the object collide with the earth or would it have been drawn by the sun's gravity away from a collision with earth? A na... | If a 1 kg object is placed at the same orbital position as Earth's core, with zero initial velocity, and the object is located on the opposite side of Earth's orbit from the Sun, how would you calculate the total gravitational influences from both the Sun and the Earth over a six-month period to determine whether the o... | 37,591 | cqadupstack-physics |
58014 | Higgs boson mass and electroweak energy scale | Is it a coincidence that the mass of the Higgs boson is exactly half the electroweak energy scale? | What is the ratio of the mass of the Higgs boson to the electroweak energy scale, and how does this relationship affect our understanding of particle physics? | 3,444 | cqadupstack-physics |
63954 | A question on lewis model | Electron affinity of chlorine = -349 kJ per mole. And, first ionization energy of sodium = 496 kJ per mole while energy required for combining= 147 kJ per mole. Isn't it a contradiction against genereal physics and G.N. Lewis' "electronic theory of valency"? | Calculate the total energy change when one mole of sodium reacts with one mole of chlorine to form sodium chloride, using the provided values: the electron affinity of chlorine (-349 kJ/mol), the first ionization energy of sodium (496 kJ/mol), and the energy required for combining (147 kJ/mol). Is the overall reaction ... | 34,570 | cqadupstack-physics |
41139 | Definition of quasi-static assumption | I'm reading this paper, where atop pg 3, the author mentions the "quasi- static" assumption for earth displacements which leads to the mechanical deformation of a fluid-solid system to be governed by: $$\nabla \sigma + \rho_h g = 0$$. What exactly does "quasi-static" mean in this context? | What is the meaning of the term "quasi-static" in the context of the mechanical deformation of a fluid-solid system as described by the equation $$\nabla \sigma + \rho_h g = 0$$, and under what conditions can this assumption be valid? | 23,676 | cqadupstack-physics |
27122 | Group of symmetries of Lagrange's equations | Consider the following statements, for a classical system whose configuration space has dimension $d$: 1. Lagrange equations admit a smaller group of "symmetries" (coordinate change under which equations are formally unchanged) than Hamilton's; 2. The 'symplectic diffeomorfism' (=coordinate changes whose jacobian i... | For a classical mechanical system whose configuration space has dimension \( d \), can you determine the relationship between the dimensions of the group of symmetries associated with Lagrange's equations and the group of symplectic diffeomorphisms? Specifically, is it true that the dimension of the group of symplectic... | 15,580 | cqadupstack-physics |
64623 | Are electrons simple? Do they have any inner structure? | The plank length is far smaller than the classical electron radius. Could the electron have structure? | Given that the Planck length is approximately \(1.6 \times 10^{-35}\) meters and the classical electron radius is about \(2.8 \times 10^{-15}\) meters, how many orders of magnitude smaller is the Planck length compared to the classical electron radius, and what implications might this have for the concept of electron s... | 2,310 | cqadupstack-physics |
20306 | Joining the definitions of entropy | $\int \frac{Q_{rev}}{T} = \Delta(k_B\ln\Omega)=\Delta S$ Could anyone give some definite proof for this? I was able to prove that the two definitions of change in entropy are equivalent for an isothermal process carried out on a gas (by quantizing space and then limiting the quantization to infinity), but my proof ma... | How can I demonstrate the equivalence of the two definitions of change in entropy, \( \Delta S = \int \frac{Q_{rev}}{T} \) and \( \Delta S = \Delta(k_B \ln \Omega) \), for a non-isothermal process, and how does this relate to the entropy of ideal gases? | 20,499 | cqadupstack-physics |
81286 | Homework Question Transformation Energy | A $1400kg$ car is approaching the hill shown in the figure at $14.0m/s$ when it suddenly runs out of gas.  What is the car's speed after coasting down the other side? I think I have to use this equation $mg(\Delta h)=\frac 12 m(\Delta v)^2 $ $(1400)(9.8... | What is the car's speed after coasting down the other side of the hill if it starts at an initial speed of 14.0 m/s and the height of the hill is known to be 10 meters? | 1,459 | cqadupstack-physics |
26826 | Quantum statistics of branes | Quantum statistics of particles (bosons, fermions, anyons) arises due to the possible topologies of curves in D-dimensional spacetime winding around each other What happens if we replace particles by branes? It seems like their quantum statistics should be described by something like a generalization of TQFT in which t... | What is the effect of k-form fluxes on the quantum statistics of branes in string theory, and how do these effects relate to generalized topological quantum field theories (TQFTs)? Provide a specific example of a non-trivial brane quantum statistic and discuss its implications. | 3,642 | cqadupstack-physics |
100854 | Reference for the renormalization of a scalar field's mass | There are a couple of interesting lectures by Leonard Susskind online, and in the first lecture on Supersymmetry & Grand Unification he explains renormalization. His example is the mass renormalization of a scalar field, and he uses a couple of dimensional analysis tricks to get his results (around 35:00). It's a nice ... | What are the precise relationships between the propagator, the bare mass, and the renormalized mass in the context of mass renormalization for a scalar field in quantum field theory? Additionally, could you provide a recommendation for a citable reference that thoroughly explains these concepts while maintaining techni... | 31,956 | cqadupstack-physics |
78802 | On Einstein's equivalence principles | There are two foundative Equivalence Principles in General relativity: **Weak Equivalence Principle (WEP):** the dynamics of a test particle in a gravitational field is independent of its mass and internal composition. (WEP is equivalent to say that the ratio between the _gravitational mass_ $m_g$ and the _inertial mas... | Can you explain why the Einstein equivalence principle (EEP) implies the weak equivalence principle (WEP), and also provide a counterexample that demonstrates why WEP does not imply EEP? | 37,024 | cqadupstack-physics |
61234 | Parton Distribution Functions, average cross section of the nucleon | Say we are given the scattering cross section for neutrinos from $d$ and $\bar{u}$ quarks as $\frac{d\sigma^{d}}{dQ^2}=\frac{G_F^2}{\pi}$, $\frac{d\sigma^{\bar{u}}}{dQ^2}=\frac{G_F^2}{\pi} (1-y)^2$, and the $u,\bar{d}$ cross sections are zero, how is the **average nucleon cross section** determined? The solution involv... | Given the scattering cross sections for neutrinos interacting with quarks, $\frac{d\sigma^{d}}{dQ^2}=\frac{G_F^2}{\pi}$ and $\frac{d\sigma^{\bar{u}}}{dQ^2}=\frac{G_F^2}{\pi} (1-y)^2$, along with the cross sections for $u$ and $\bar{d}$ quarks being zero, how do you calculate the average nucleon scattering cross section... | 2,170 | cqadupstack-physics |
93912 | Riemann normal chart and special relativity | When you pick Riemann normal coordinates at a point, then the Christoffel symbols vanish and the metric is flat, but the Riemann curvature tensor does not necessarily vanish. Since Einstein said that locally the laws of special relativity hold, how does that reconcile with the Riemann curvature tensor not being zero (w... | In a Riemann normal coordinate system centered at a point in a curved spacetime, the Christoffel symbols vanish, and the metric appears flat. Given this condition, how can you quantitatively describe the relationship between the non-zero components of the Riemann curvature tensor and the deviation of the spacetime from... | 36,819 | cqadupstack-physics |
12783 | Glass and isotropy | Glasses are amorphous materials. Nevertheless, as far as I know, in some areas of Condensed Matter, they consider that the glass is isotropic. Under what restrictions they can do this assumption? Mathematically, the assumption that glasses are isotropic make the calculations, in my imagination, dramatically simpler. In... | Under what conditions can glasses be approximated as isotropic in the context of Condensed Matter physics, and how does this assumption simplify mathematical calculations related to their physical properties? Additionally, could you provide references that discuss the isotropic nature of glasses? | 27,040 | cqadupstack-physics |
53353 | Weightlessness on Earth | Would the following work? Imagine one would 1) create a straight 4000 km long tube (at ground level), following the curvature of the Earth, wide enough to hold a pod the size of an aircraft cabin; 2) remove the air in front of the pod and make sure it accelerates to a speed of 28000 kph. Would one achieve weightlessnes... | If a pod the size of an aircraft cabin is placed in a tube 4000 km long that follows the curvature of the Earth, and the air is removed to allow the pod to accelerate to a speed of 28000 kph, how long would it take for the occupants inside the pod to experience weightlessness, if at all? What physical principles and ob... | 16,843 | cqadupstack-physics |
51962 | Probability and probability amplitude | The equation: $$P = |A|^2$$ appears in many books and lectures, where $P$ is a _"probability"_ and $A$ is an _"amplitude"_ or _"probability amplitude"_. What led physicists to believe that the square of modulus connects them in this way? How can we show that this relation really holds? In a wonderful QM lecture by J. J... | Can you explain the derivation of the equation \( P = |A|^2 \) in quantum mechanics and describe a simple experiment or thought experiment that illustrates how the probability of finding a particle relates to the square of the modulus of its amplitude? | 1,447 | cqadupstack-physics |
55086 | Is it possible to condense heat? | Suppose that I have a warm room. Is it possible to condense the heat of the room into a small object so that the room turns cold and the small object very hot? If it's possible: How? If it's not: Why? | Is it possible to transfer heat from a warm room to a small object, resulting in a significant temperature decrease in the room and a corresponding significant temperature increase in the object? If so, describe a method to achieve this while providing the energy values needed for both the room and the object involved.... | 34,793 | cqadupstack-physics |
123026 | What's the conserved quantities correspond to the generator of conformal transformation | What's the conserved quantity corresponding to the generator of conformal transformations? | What is the conserved quantity associated with conformal transformations in a physical system, and how is it derived from the symmetry principles? | 36,250 | cqadupstack-physics |
56833 | Slinky base does not immediately fall due to gravity | Why does the base of this slinky not fall immediately to gravity. My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.  | What are the forces acting on the base of a slinky when it is dropped, and how do these forces relate to the weight of the slinky and the tension in its springs? Calculate the tension in the springs necessary to prevent the base from falling under the influence of gravity immediately after release. | 37,508 | cqadupstack-physics |
82810 | Does space expansion imply light will *never* reach objects currently distant enough? | Let's say two objects are at about twice the Hubble Distance from each other. One of them emits light towards the other. When light emitted from one reaches the Hubble Distance from its origin (within less than Hubble Time, but more than half of it) the other will be more than another Hubble Distance farther from the f... | If two objects are initially separated by a distance of twice the Hubble Distance and one emits light towards the other, how much farther apart will they be when the light reaches the point that is one Hubble Distance from the emitter? Assume the universe is experiencing accelerated expansion during the light's travel ... | 20,962 | cqadupstack-physics |
132482 | Sound difference between musical instruments | I know that the difference between two musical notes is given by the sound frequency, and the difference in volume is given by the amplitude. What I am wondering is why does the same note sound different on different musical instruments? What in the wave makes the difference between the sound of a harmonica and the sou... | What are the key factors in sound wave characteristics that differentiate the timbre of a harmonica from that of a violin, even when both are producing the same musical note? | 2,130 | cqadupstack-physics |
62009 | Question on hadamard gate and cnot gate circuit tables | I'm trying to solve this problem for homework: > Now show that if the **CNOT** gate is applied in the Hadamard basis - i.e. > apply the Hadamard gate to the inputs and outputs of the **CNOT** gate - > then the result is a **CNOT** gate with the control and target qubit > swapped. So I've computed the truth table for $a... | What is the mathematical representation of the state of qubits \(a\) and \(b\) after both have passed through a Hadamard gate, and how would you describe the result of applying a CNOT gate with \(b\) as the control qubit on these states? | 36,419 | cqadupstack-physics |
73706 | Can inertia be explained by Bremsstrahlung? | Considering that on the atomic level objects consists of densely spaced positively and negatively charged particles, does not the acceleration of those objects lead to Bremsstrahlung of those particles? And although the monopole field is zero, couldn't higher order multipole radiation escape and cause the inertia? I wo... | How does the emission of Bremsstrahlung radiation from accelerated charged particles relate to the effective mass or inertia of a macroscopic object, and can you quantify this effect for an object comprised of a specific number of elementary charged particles? | 34,575 | cqadupstack-physics |
90929 | Tape adhesive force | So I was bored and had some clear Scotch tape nearby. Decided to mess around, and now I have questions. * What is the physics behind the force of tape adhesive? * Why does the tape hold so much better if it is pulled parallel to the surface plane it is on? (Excuse my poor drawing skills) * Is there a rating for... | What is the relationship between the surface area of an adhesive tape applied to a surface and the force required to detach it from that surface, and how can this relationship be quantifiably measured in an experiment? | 1,093 | cqadupstack-physics |
95731 | Virtual-work problem | I have a very specific doubt about the next exercise: I have the crane of the picture:  With a force $F_a=-K\varphi$ Applied on the point B, perpendicular witch AB, and another force $F_b=-K\psi$ Applied on the point C. They ask me to find an equilibriu... | In a crane system where arm AB is rotated by an angle \( \varphi \) and arm BC by an angle \( \psi \), with respective forces \( F_a = -K\varphi \) and \( F_b = -K\psi \) applied perpendicularly to the arms, if the position vector \( r_1 \) from point A to point B is defined in a moving basis, how does the virtual disp... | 3,977 | cqadupstack-physics |
114126 | Scattering of two particles - phase factor | I did see some posts on stackexchange on this matter, but I find them to be beyond my scope or not directly related to what I am looking for. I am reading Feynman Lectures III, chapter 4. It talks about scattering of two particles $a$ and $b$ and it defines $f(\theta)$ to be the probability amplitude of particle $a$ sc... | In the context of quantum scattering, if the probability amplitude for particle \( a \) scattering at angle \( \theta \) is defined as \( f(\theta) \), what is the relationship between \( f(\theta) \) and \( f(\pi - \theta) \) when taking into account the possibility of an arbitrary phase factor? Can you provide a math... | 1,698 | cqadupstack-physics |
93933 | Circulation of the gauge potential around an infinitesimal loop: how to get the correct gauge field strength tensor | I've been puzzling with the problem below for more than a hour since it is misleadingly discussed in some textbooks, so I believe it deserves a solution here. Any comments are welcome. I'm trying to calculate the gauge field strength tensor from the circulation of the gauge potential around an infinitesimal loop. The b... | Can you derive the expression for the gauge field strength tensor \( F_{12} \) from the circulation of the gauge potential \( A \) around a closed square loop defined by the points \( A(a,b) \), \( B(a+\delta a,b) \), \( C(a+\delta a,b+\delta b) \), and \( D(a,b+\delta b) \) using the path-ordered transport operator \(... | 25,770 | cqadupstack-physics |
52283 | Revealing Electric field lines through Grass seeds in mineral oil | In one of Walter Lewin's famous lectures, he takes a small container almost completely filled with mineral oil and grass seeds (I'll keep looking for the video to link to it). He connects two electrodes to the container and the electric field that is produced polarizes the grass seeds, aligning them in the direction of... | What is the minimum voltage required to polarize grass seeds in mineral oil, given that the dielectric constant of the oil is approximately 2.2? | 22,062 | cqadupstack-physics |
74237 | What are Einstein evolution equations? | In my studies I faced "Einstein evolution equations". I know about "Einstein equation", but I don't know what are "Einstein evolution equations"? Unfortunately, my searches did not result in much. Can anyone help me? | What are the Einstein evolution equations in the context of general relativity, and how do they relate to the Einstein field equations? | 29,494 | cqadupstack-physics |
5403 | List of theories supporting origin of universe | Big Bang theory is widely accepted theory when it comes to origin of universe. What other really compelling theories are out there explaining/supporting the origin of universe. I know many people don't believe in Big Bang theory for various reasons. **Update** Question was not complete before for some reason. | What are the key differences in the predictive capabilities of the Big Bang theory compared to the Steady State theory in explaining the origin of the universe, and what observable evidence supports or contradicts each theory? | 5,590 | cqadupstack-physics |
90173 | Why does $\ell=0$ correspond to spherically symmetric solutions for the spherical harmonics? | In quantum mechanics why do states with $\ell=0$ in the Hydrogen atom correspond to spherically symmetric spherical harmonics? | What is the probability density distribution of the electron in a Hydrogen atom when it is in a state characterized by quantum numbers \( n=1 \) and \( \ell=0 \)? | 7,968 | cqadupstack-physics |
106835 | Planetary Systems | How does one know the correct position of planets in relation to the sun when viewing the solar system from different angles makes the appearance of the planets different? I would think that it would require a satellite to orbit in a circular pattern above and below the entire solar system to get correct bearings. | If a satellite orbits the solar system in a circular path at a constant height above the solar plane, what minimum altitude must it achieve to have a clear line of sight to all planets at their farthest point from the sun, assuming they are located in the same plane? | 11,062 | cqadupstack-physics |
88152 | What does it mean to be stationary? | I'm looking for a simple answer. What do we regard a stationary. Do we mean an object that is not moving noticeable from the viewers perspective because then a parked car would be considered stationary, but (assuming it's on earth) the earth is rotating and those at the circumference where the spin is greatest are trav... | Considering the Earth's rotation and its movement within the Milky Way galaxy, if an object is observed to be stationary from a viewer's perspective, what speed are we ignoring when we classify it as such, assuming the object is on the surface of the Earth? Calculate this speed in miles per hour (mph) for an observer l... | 5,424 | cqadupstack-physics |
6262 | Identifying unrealistic traits of this exoplanet. There are a few obvious ones, but I cant find them all. Help! | I need to find the inaccuracies of this computer generated picture, the picture shows a non existent exoplanet. I need to identify the unrealistic features of the planet and its surroundings and write an essay on some of them. The image is located here: http://i.stack.imgur.com/zXrPy.jpg Could you help point out some o... | What specific features in the provided image of the exoplanet might indicate that it cannot exist according to our current understanding of planetary formation and environmental conditions? Identify at least three features and explain why they are unrealistic based on known astronomical principles. | 21,364 | cqadupstack-physics |
96642 | Block on cart, equation of motion | Consider a rigid block of $b \times h$ having mass $m$ on cart (as depicted below). The cart is given an acceleration $a$, this leads to overturning of the block. The angle of rotation is indicated by $\theta$.  This is how far I got (not considering the mov... | Given a rigid block of dimensions \(b \times h\) and mass \(m\) placed on a cart that accelerates to the right with acceleration \(a\), what is the critical acceleration \(a_c\) at which the block begins to overturn, assuming the angle of rotation \(\theta\) is small and using the relationship between torque and angula... | 34,764 | cqadupstack-physics |
20907 | What does activation energy actually do? | Spontaneous (exothermic) chemical reactions often require a push from the addition of externally supplied energy. This energy is often called activation energy. What does activation energy actually do? What is the energy hill that the activation energy surmounts? | What is the minimum amount of activation energy required for a given spontaneous exothermic reaction to occur, and how can this energy be quantified in terms of temperature and reaction rate? | 11,587 | cqadupstack-physics |
15565 | Schrodinger's dead cat when the evidence is destroyed | In the classic (and morbid) _Schrodinger's Cat_ thought experiment, we imagine putting a cat into a box with a vial of poison which will be triggered by a quantum detectors. We set up a radioactive nucleus or an excited ion, and set up a detector to look for radiation resulting from radioactive decay or drop to the gro... | If we consider a sealed box containing a cat and a quantum system that can lead to its potential death, what is the probability of the cat being alive or dead after a set amount of time, assuming the radioactive decay follows a half-life of 10 hours and the experiment is run for 30 hours before the box is exploded? | 15,173 | cqadupstack-physics |
110577 | A simple question about special relativity |  Assume that the table moves with the velocity $\vec{v} = v\hat{i}$. For the observer at $x=0$, the event at $(ct',x')=(0,k)$ is observed at $(t,x)=(k\gamma\beta, k\gamma)$ using Lorentz's transformation $L(v) = \gamma\bigl(\begin{smallmatrix} 1&\beta\\... | A table moves with a velocity \( \vec{v} = v\hat{i} \). For an observer at \( x=0 \), the event at \( (ct',x')=(0,k) \) is seen at \( (t,x)=(k\gamma\beta, k\gamma) \) using Lorentz transformation. For an observer at \( x=4 \), how is the event observed at \( (ct,x) \) for \( k=1, 2, 3 \) using the Lorentz transformatio... | 13,935 | cqadupstack-physics |
28795 | Is it possible to mould _ruptures_ in Space-time? | In one of the documentaries hosted by Morgan Freeman, a reference was made that just like an ordinary three-dimensional object like a ruler has scratches and cracks, in the same way there might be minuscule loops in space-time. My question is this: If many bodies of extremely high densities are brought close together, ... | If two massive celestial bodies, each with a mass significantly greater than the Sun, were to come extremely close to one another, what quantitative effects could we expect on the curvature of space-time around them, and would this interaction potentially create permanent loops or distortions in the space-time fabric? | 14,387 | cqadupstack-physics |
76861 | What are the equations of motion of a hole in a soap bubble? | Imagine the following situation: I have a thin stationary water film, like a soap bubble, suspended inside a large ring. I throw a small loop of string onto the film and punch a hole inside it. How can I describe the motion of the hole in the water film bounded by the loop of string? The surface tension of the surround... | In a thin water film resembling a soap bubble suspended within a large ring, a small loop of string is thrown onto the film, and a hole is punched in it. If the mass of the string is less than the mass of the water film defined by the inner boundary of the string, how does this affect the motion of the hole in the film... | 26,974 | cqadupstack-physics |
23468 | Magnetic flying engine | I invented a flying engine moving entirely by magnetic forces (such as the force related with magnetic field of the Earth). See http://porton.wordpress.com/2011/12/23/magnetic-vehicle/ The question is, can we build an engine of this type which is enough powerful to actually fly? The question is both about the mechanica... | What are the key operating characteristics and efficiency parameters of a flying engine that utilizes magnetic forces for propulsion, specifically focusing on both mechanical and purely electronic designs? Include calculations for the necessary magnetic field strength and power output required for it to achieve lift in... | 855 | cqadupstack-physics |
131039 | Is there a material with non-monotone density dependence on pressure? | Is there a material with such non-linear effects (including chemical reactions, phase transitions etc ...) so that there would be range where pressure increase would yield density decrease? What would be the answer if we consider volume instead of density? | Can you provide an example of a material that exhibits non-linear effects, such as phase transitions, where an increase in pressure results in a decrease in volume? Additionally, how does this behavior compare if we consider density instead of volume? | 29,252 | cqadupstack-physics |
57876 | Projectile's angle in midflight | For a missile travelling from (0,0) at angle $\theta$ (to the horizontal) and initial velocity $u$, the y (vertical) position at time t is given by $s_{y} = u\sin (\theta) t - 0.5gt^{2}$ and the x position id $s_{x} = u\cos(\theta)t$, but I am struggling to calculate the angle $\theta_{t}$ at time $t$ to the horizontal... | A missile is launched from the origin with an initial velocity \( u \) at an angle \( \theta \) to the horizontal. The vertical position \( s_{y} \) and horizontal position \( s_{x} \) of the missile at time \( t \) are given by \( s_{y} = u\sin (\theta) t - 0.5gt^{2} \) and \( s_{x} = u\cos(\theta)t \), respectively. ... | 19,898 | cqadupstack-physics |
20301 | CSI Miami and other TV series on application of physics and science in life and career opportunities | Sometimes I volunteer to help freshmen and sophomore students with introductory physics and calculus courses. The problem is most of them are not stimulated and take these courses because they are obligatory. On the other hand some TV series, such as CSI Miami, contains scenes which show how some of the technologies th... | What are some examples of scientific principles depicted in popular TV shows like CSI Miami, and how accurately do they represent real-life physics, biology, or chemistry concepts? | 28,330 | cqadupstack-physics |
128277 | Molecular field meaning in Liquid Crystal Theory | Given the Frank-De Gennes free energy $F = \int f(\boldsymbol{p},\nabla\boldsymbol{p}, ...)\ d\boldsymbol{x},$ for liquid crystals (see De Gennes-Prost, p. 107, formula 3.21), the vector $$h_{i}=-\frac{\delta F}{\delta P_{i}}=-\frac{\partial f}{\partial P_{i}}+\partial_{j}\frac{\partial f}{\partial\partial_{j}P_{i}}$$ ... | What is the physical interpretation of the molecular field vector \( h_{i} = -\frac{\delta F}{\delta P_{i}} \) in the context of liquid crystals, and how does this concept relate to the behaviors of magnetic systems? Moreover, is it appropriate to label this vector as "molecular" in this context, and why? | 32,598 | cqadupstack-physics |
38841 | What's the Significance of Color Changes Between EM-Spectrums? | As everybody knows that Black objects are black because almost all the light that falls on them is absorbed into the material. Little or no light is reflected back toward our eyes, therefore we see black. It is also known that, since black objects absorbs all the light they ultimately become heated-up..! If we see the ... | If snow appears black in infrared light, does it absorb infrared radiation and therefore become warmer than in visible light, where it appears white? Quantify the difference in temperature change for snow exposed to visible light versus infrared light. | 14,597 | cqadupstack-physics |
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