# All Questions

0answers
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### Meaning of Eigenvalues/Eigenvectors of a linear system of equations

I have a 41x41 system of linear equations (inhomogen) which I derived with Eureqa by describing the timecourse of fMRI haemodynamic data from a brain area as a function of the timecourses of 40 other ...
0answers
23 views

### Can unexposed PMMA be reused (successfully exposed) after development?

Can unexposed PMMA be reused (successfully exposed) after development? To clarify, PMMA is exposed using an electron beam in an SEM, and then the exposed areas are removed using a developer solution, ...
1answer
106 views

### What does non magnetic and nonconducting mean in reflection and transmission of waves?

So, we were ask to consider the Fresnel Equations for parallel and perpendicular waves (with index of refractions). Then, we are ask to prove some equations in which "... for nonmagnetic ...
1answer
215 views

### Scanning Electron Microscopy: Explanation of Numerical aperture and Extraction Field

I am trying to understand what numerical aperture and extraction field means in a scanning electron microscope. From what I understand numerical aperture is used to set the Depth of Focus which is ...
0answers
62 views

### Notation for Propability Amplitudes

I've recently stumbled upon a certain piece of notation that doesn't quite seem clear to me. When discussing the amplituhedron, my teacher mentioned the relation between the volume and the amplitude ...
1answer
287 views

### Why light can't go faster then 300 000 km/s? What prevents it? [duplicate]

Why can't the speed of light be faster then approx 300 000 km/s? What prevents it?
1answer
1k views

### How to find power factor value of parallel RL circuit knowing the power factor value for the series circuit with the same components

Because I know the value for the power factor for the series RL circuit I've tried to find the ratio between the series circuit power factor and the parallel circuit power factor, expressed in terms ...
1answer
163 views

### Difference between Cotton Mouton effect and inverse Cotton Mouton effect

The Cotton mouton effect is observed when a linearly polarized electromagnetic wave passes through a dielectric medium and a magnetic field is applied perpendicular to the direction of propagation of ...
3answers
149 views

### Animating an Acceleration Vector - Acceleration of object on a crested path in gravitational field

So I was reading in Chapter 3 of my textbook, Sears & Zemanksky's University Physics with Modern Physics by Young and Freedman, 13th Edition, and the discussion took us to a definition of the ...
1answer
117 views

### Why Thermodynamic cycles and no single process

Why Thermodynamic cycles are used to obtain work for example carnot engine rather than single isothermal process which is part of cycle and can be used to obtain more work.And why isothermal process ...
0answers
44 views

### Determining impact velocity over long distances [duplicate]

Everything I have found concerning impact velocity from a given height deals with constant acceleration due to gravity. I would like to know how to work in varying acceleration into the equation. So, ...
2answers
251 views

### Tangential acceleration in circular motion?

A lot of my problems have objects moving in circular paths with tangential and normal components of acceleration. If the tangential component is non-zero though, the speed is changing so the radius ...
1answer
68 views

### how does the temperature of a gas increase when compressed by an external agent during sound production? [duplicate]

Suppose a vibrating tuning fork compresses air molecules.And for this it has to do work.As compression occurs,its temperature increases.Does the energy spent by the fork go as the increased internal ...
0answers
62 views

2answers
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### Electrostatics kinematics equations (Coulombs Law)

If there are two similarly charged particles $Q$ and $q$ of masses $M$ and $m$, a Coulomb force is applied on each one (action-reaction). Suppose that $Q$ is stationary and we are shooting $q$ with an ...
0answers
39 views

### Help me understand virtual images versus real images [duplicate]

Simple question; Is a virtual image that is produced by a lens always - in front of or in back of the lens?
0answers
42 views

### Doppler broadening: time scale to frequency scale

Consider a cell containing Rubidium and enlight it with a laser. Connect the system with an oscilloscope and give a triangular wave as input (so you can know when the Rubidium is resonant). This is ...
1answer
114 views

### Is there a closed form expression for Landau-level eigenstates?

Is there a closed form expression for the Landau-level eigenstates (preferably in the symmetric gauge)? This is the 2-dimensional quantum mechanical problem of a charged particle moving in a ...
0answers
69 views

### Spectroscopy: clarification about doppler shift

I've just begun to study spectroscopy, and I need a clarification about the Doppler Effect. Considering this graph: could you explain me how I can see the doppler shift related to the deeper peak ...
0answers
111 views

### Simulating orbits using Newton's Law of Universal Gravitation

I've been having a go at programming an orbital simulator from scratch (without using any existing libraries) using the formula below to find the acceleration first for particle A and then for ...
0answers
76 views

I've been searching the internet for a formula for nuclear mass which accounts for various interactions present. I've encountered the following formulas: $$m = Zm_p + (A-Z)m_n - \frac{B}{c^2}$$ $$m ... 0answers 50 views ### Work done on an object from different frames Consider this situation: A car is moving on a road and applies brakes. The road exerts a force F on the car, due to which the car stops in S meters. Clearly, the work done by the road on the car ... 0answers 213 views ### Finding moment of inertia from Lagrange equation I'm getting the following information: Consider a system consisting of two rotating bars of length \ell and with uniform mass density and each with total mass m. The bars are attached to a common ... 0answers 165 views ### Has the Reissner-Nordstrom metric ever been experimentally verified? In contrast to the solution of the conventional Reissner-Nordstrom problem, where the Schwarzschild metric takes on an additional 1/r^2 term due to the added electric charge, P. Mannheim has in ... 0answers 192 views ### Why do electric generators need a prime mover? Commonly electric generators need a mechanical torque provided by a prime mover [gas turbine or steam turbine or diesel engine,etc] which is needed for the rotation of the generator rotor. I would ... 0answers 63 views ### When do wave function collapse in this case? In relativity, an event A can occur before another event B in one frame while A may occur after event B in another. In quantum mechanics, we may measure the spin of two entangled electrons: If you ... 0answers 134 views ### How do I measure the total weight of a container with scales on four corners? I have a very large movable trash container, and I have mounted four scales, one on each corner. How do I get the total weight of the entire container? Is it simply a sum of the four weights, or is it ... 2answers 97 views ### Is crystal momentum an operator? My teacher has for Bloch waves the notation \langle \vec{r}|\vec{k} \rangle = e^{i\vec{k}\cdot \vec{r}}u_{\vec{k}}(r) and uses it consistently. However, does this not assume that there is an ... 0answers 341 views ### Caculating thermal stresses in a composite rod The Question Between two rigid walls separated by a distance l_1+l_2, two rods of equal cross-section area A, and length, coefficient of linear expansion and Young's modulus l_1, ... 0answers 45 views ### Expanding the Magnetic field? A magnetic field B can apply a force X on a ferromagnet when there is no gap to separate them, r = 0. When that gap (r) is increased to 3 cm, the force drops to zero. How can that be solved? ... 0answers 25 views ### Finding out the temperature difference If we add 10 spherical bubbles then there will be some change in their area. Is there any way to find out change in temperature of the liquid from the change of its area? 1answer 28 views ### How do you interpret the product of two components? I hope this isn't borderline philosophy. It is really difficult for me to articulate the question and so Google was of no use to me. The question spawned when I was learning laws of conservation of ... 0answers 90 views ### Timelike Shell Collapsing into a Black Hole Does anyone know where I can find the solution for a spherically symmetric thin shell of timelike matter falling into a Schwarzschild black hole? The matter should be pressureless, so that each ... 1answer 185 views ### What's a good book for an advanced undergraduate/early graduate student to learn about symmetry, conservation and Noether's theorems? What's a good book (or other resource) for an advanced undergraduate/early graduate student to learn about symmetry, conservation laws and Noether's theorems? Neuenschwander's book has a scary review ... 1answer 135 views ### How is matter stored in black hole? A black hole engulfs the matter nearby, how does it store the mass inside? We know that matter is composed of particles, does a black hole store the mass in massive particles? Or can we assume that ... 0answers 18 views ### Resistor connections [duplicate] I can't figure out what kind of connection it would be if i put resistors like this Can someone please explain how they are connected, like is R1 and R2 in series and R4 and R5 in series and then I ... 0answers 286 views ### Shape of the “flow head” in Laminar flow in pipe Laminar flow is a streamlined steady flow with a uniform gradient of velocity across the diameter of the pipe. I am familiar with the elementary treatment of laminar flow, like basic velocity ... 0answers 343 views ### What about assessing negative Limit of Detection for concentration I recently came in a work-group discussion where I think some concepts are misused. After seeking for scientific articles on the subject I have found that part of the problem is definition (what ... 2answers 344 views ### Is it possible to use induction ampermeter to measure power consumption of electric water heater and dryer? I hope this practical question is not OT and not too trivial for this forum. I am renting an apartment in a duplex with a shared water heater and dryer. Turns out, both water heater and the dryer are ... 0answers 85 views ### Is the black hole surface area actually zero? From quantum mechanics we know that entropy of a part can be smaller than the entropy of the whole. I wonder whether a similar rule works for GR as well. Quantum mechanics predicts that the entropy ... 0answers 53 views ### What is the nature of energy? [duplicate] In science fiction adventures, spacecraft are sometime equipped with "energy beams", i.e. devices that can project pure energy unassociated with matter. Is this possible? Is energy a "thing" in the ... 0answers 1k views ### Damping ratio and damping coefficient of two objects connected by spring There are two objects m1 and m2 connected by a spring and a viscous damper (e.g car body and wheel connected by spring) From wiki: \zeta ={c \over 2{\sqrt {mk}}} ζ is damping ratio, c is damping ... 0answers 14 views ### Find the position of the final image [duplicate] I was going through Geometrical Optics and came across the following question in my textbook: Q. An object is placed 21 cm in front of a concave mirror of radius of curvature 20 cm. A glass slab ... 0answers 104 views ### Curvature based derivation of Schwarzchild Metric I'm a third year maths undergrad and I'm trying to find (and follow) a curvature based derivation of the Schwarzchild metric, if there exists such a proof? 0answers 185 views ### Need to find the Vab of this circuit! [closed] Find Vab in the circuit http://imgur.com/IqZ7Yis I uploaded a picture of the circuit. I tried adding 10 and 5 (top) because they appear to be in series. I also added 10 and 15 (bottom two) because ... 0answers 170 views ### How fast do large asteroids usually travel? I have just watched this video made by discovery channel, and you can hear the narrator at 0:51 saying that : "even though it is moving at 720 THOUSANDS kilometers per hour..." I stopped once I heard ... 0answers 61 views ### Confusion about the (relativistic) mass of objects [duplicate] According to Einstein's theory the (relativistic) mass of objects depend on speed. Then in an inertial reference frame 2 observers moving at 2 different velocities will calculate different masses for ... 0answers 255 views ### Why does Hydrogen bubbles gather in anode instead of cathode during electrolysis? Just wondering when water undergoes electrolysis why does oxygen goes towards cathode and hydrogen towards anode why not the other way round 0answers 109 views ### Perturbation of a Hydrogen Atom in a Quadrupole Field Question: A hydrogen atom is located in a quadrupole field, which gives it a perturbation$$H_1=A(x^2-y^2) where $A$ is some constant. Calculate the ...

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