# All Questions

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### Relationship between tones made by a piano

If a piano were to be tuned perfectly with the equal temperament system, what would be the relationship between standing waves from one note to the next? How would the frequency and wavelength of ...
519 views

### Best way to chill a cup of coffee with cold water and 5 minutes [duplicate]

Initial data 1 x 3/4 full cup of hot coffee / tea / your favorite morning beverage cold water 5 minutes Considering that it's starting to get hot outside, and we all want to drink reasonably cold ...
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### Cheaply measuring torque required to turn small screw

The small screw is a plastic drip-line variable-flow water valve. My plan is to glue a constant-width arm to the head of the valve, put the thing in a vise and stack pennies on the end of the arm ...
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### Why aren't there more than three generations of the leptons and quarks? [duplicate]

There are three generations of electrons, neutrinos, and quarks. The second and third generations of electrons and quarks are unstable and decay into lighter particles. Why are there exactly three ...
49 views

### Energy in a wind instrument?

My physics teacher said that he saw a guy playing a very large wind instrument on TV, and the guy apparently calculated that the total energy present in the instrument when he was playing was almost ...
150 views

### Is there anything smaller than a quark? [duplicate]

I've gotten interested in physics recently due to the many educational channels on YouTube such as sixtysymbols and minutephysics. They talk about quarks sometimes, and I was wondering if there is ...
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### Non-dimensionalization for spatially varying material parameters

For a homogeneous material of length $L$, we can write the heat equation as $$\rho c\frac{dT}{dt}=k\frac{du^2}{dx^2}, \text{ } x\in (O,L)$$ where $T$ is the temperature, $\rho$ is the thermal ...
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### What to look for in a discrete fourier transform [migrated]

I was attempting to do a discrete Fourier transform through a computer program on a list of numbers. Before doing that I decided to test it by running through a list of 1000 numbers which I created by ...
24 views

### Balmer absorption lines

I'm having a bit of trouble understanding Balmer lines, is this correct, and the questions are in brackets: 1) A star needs to be hot enough such that electrons are in the n=2 state (why does the ...
117 views

### What is the deal with heat capacity?

For some time now I've been confused about heat capacity. The way I understand it, if I put in an amount of heat energy into the system, $dQ$, its temperature will change by $CdT$. But now, ...
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### What is the equation for Lin-Shu density wave theory?

Lin-Shu density wave theory is a (very good) theory to explain the spiral arm structure of spiral galaxies. Where can I find the equations that underlie this theory? I've seen its computer ...
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### Is it incorrect to explain the direction of a coded vector quantity?

For example, let's say that in a linear physics problem, all the data are given to a certain direction, and coded positively for direction to the right. So +5m/s would be a velocity of 5m/s to the ...
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### Chemical Equilibrium - Why does changing the temperature shift the equilibrium? [migrated]

I know that raising the temperature in a reversible chemical reaction causes the equilibrium to shift to the endothermic side. I know that $\Delta G = \Delta H - T \Delta S$ but I don't know how to ...
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### Have general relativistic effects of all of the components of the stress-energy tensor been measured?

The stress-energy tensor is: Have general relativisic effects of all of the components of the stress-energy tensor been measured? I've heard that the accelerating expansion of the universe is due to ...
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One end 'A' of a wire AB is radiated with $\alpha$-rays and other end 'B' with $\beta$-rays. Then: (A) Current will flow from 'A' to 'B' (B) Current will flow from 'B' to 'A' (C) Current will ...
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### Is this a correct description of bonding in a metal?

I am reading the paper "Twenty five years of Finnis-Sinclair potentials" by Graeme Ackland, Adrian Sutton, and Vasek Vitek, Philosophical Magazine 2009, 89, 3111-3116. It is a review-type article ...
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### Decomposition of this wave function in eigenfunctions

I have this wave function of a system on a central potential: $V(r)$: $$\Phi(x,y,z)=C(x+y+z)e^{-\alpha r^2}.$$ And I'm asked a few things about probabilities. I don't have problems with that, because ...
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### Photometric versus radiometric and spectral quantities

Are spectral quantities the same as photometric quantities? How do you pass from a radiometric quantity $R$ to the correspondent spectral quantity $R_λ$ I've been ask to pass from Irradiance to ...
37 views

### Could path integral formulation be applied to path tracing?

Firstly I have a very shallow knowledge of physics and what I'm about to say may not make any sense at all, I'm just wondering if this could be applied. The wiki on path integral formulation states: ...
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### Is there any other mathematical tool to measure velocity, instead useing derivative? [closed]

To measure velocity we use derivative $$v=\frac {dr}{dt}.$$ Is the any other mathematical tool to do this?
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### A few questions related to frame dragging

I am trying to get my head around a few concepts related to frame dragging and related physics. In regards to black holes that have no charge and all thier mass is tied up in rotational kinetic ...
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Imagine a non-linear elastic material such as a rubber band, nylon webbing or polyester webbing tensioned between two points. Scenario 1: A large mass is statically (no acceleration) loaded onto the ...
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### Mass conversion to energy [closed]

My teacher asked me to give an example for the 100% conversion of mass to energy. to the molecular level. My answer is "quantum teleportation". Is it right? Are there any other example?
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### How big of a telescope to view Gliese 581g in great detail?

I've always been interested in mega sized telescopes and how big they would have to be to see exoplanets in great detail. So, Gliese 581g is 22 light years away. Could we build a telescope in space ...
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### Why do the mismatched 16 dimensions have to be compactified on an even lattice?

The mismatched 16 dimensions between the left- (26 dimensional) and right- (10 dimensional) are compactified on even, unimodular lattices. I think I get the unimoduar part, at least intuitively, ...
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### Are higher order mixed partial derivatives of wave function with different ordination equal?

For example, given two operators: $$A = \frac{\partial}{\partial x}+\frac{\partial}{\partial y},$$ $$B =\frac{\partial^2}{\partial x^2}+\frac{\partial^2}{\partial y^2} + 1.$$ Deriving commutator ...
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### Why does asphalt crack along painted lines?

My elementary school playground was made of asphalt and had a track painted on with white lines. While walking on the track, I noticed that cracks in the asphalt often followed the paint. The ...
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### Conservation of Energy and Quantum Fluctuations

Regarding conservation of mass-energy Wikipedia says: "this is an exact law, or more precisely, has never been shown to be violated." However, regarding quantum fluctuations, Wikipedia says here: ...
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### Experimental study of the Photoelectric effect [duplicate]

As I was reading about the experimental arrangement for photoelectric effect, I saw a diagram that puzzled my knowledge of electrodes. I found that in the experimental setup the cathode of the ...
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### Electricity directly from heating a material [duplicate]

I am looking for some more information about how to obtain electricity from heat directly. This e.g. involves the Seebeck effect, as I have found it is called, where a material produces a voltage ...
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### Is there an equation that tells you more about the amplitude of an object which is in resonance?

I'm a high school senior and I have to write a paper about resonance and differential equations. I've been searching the Internet for a long time, but I haven't found an equation that is properly ...
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### Physics question based on motion in one dimension [closed]

2 trains $A$ and $B$ are moving in same direction at same track with $B$ ahead of $A$ with speed $u$ and train $A$ with speed $v$ ($v>u$). The driver of $A$ sees $B$ and starts decelerating with ...
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### what happens to the angular velocity of star in star-black hole system?

What happens to the rotational and revolutionary angular velocities of star in star-black hole system as the star loses mass ?
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### How does the Cern LHC collide particles head on if uncertainty principle limits the precision

I have been wondering why doesn't the uncertainty principle prevent the LHC experiment as if one want to collide two particles together one must accelerate a particle to certain speed and aim it at ...
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### Finding the Horizontal Acceleration of an Object in Projectile Motion (Air Resistance)

In a program I'm working on I'm trying to demonstrate how objects trajectory can be affected by the horizontal acceleration, or shall I say air resistance. I'm wondering, if for example there was a ...
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### IR divergence and renormalization scale in dimensional regularization

Is it possible that if a certain (loop) integral is IR divergent then that will have effect on the dimensionally regularized answer for that? (..does the epsilon expansion see the IR divergence in ...
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### In a turning plane, will the vector of combined centrifugal plus gravity force experienced by passengers be perpendicular to the floor?

In a turning plane, will the vector of combined centrifugal plus gravity force experienced by passengers be perpendicular to the floor? In other words, will the passengers experience the feeling of ...
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### Is it possible to generate electricity using a water tower?

Is it possible to build a water tower that will provide enough pressure to run an electricity generator? A water pump can be used to send water up to the tower. The water pump can be powered by solar ...
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### Is faster than light travel possible using nothing but ordinary matter and special relativity? [closed]

Ok so technically not faster than light from the point of the traveling object but my question is this: Forget for this thought experiment the impossibility of creating this arrangement but - what if ...
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### Why do stars flicker?

Why do stars flicker and planets don't? At least this is what I've read online and seen on the night sky. I've heard that it has to do something with the fact that stars emit light and planets reflect ...
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### Why can't some light ever reach earth? [duplicate]

Note: I'm a layman in physics. Excuse me if this question is a duplicate, I lack the knowledge in technical terms to find the answer to this by research (I've tried). Let's suppose there's a star ...
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### Toward the establishment of non-equilibrium (quasi-equilibrium) magnon BEC theory

In 2006, Demokritov et al have reported that they have achieved the observation of quasi-equilibrium magnon Bose-Einstein condensation (BEC) in YIG at finite (room) temperature by using the method ...
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### Esd safety when working with printed ciruct boards. What is the risk of damaging circuit boards when working in non esd safe chair, vs a esd chair?

esd safety when working with printed ciruct boards. What is the risk of damaging circuit boards when working in non esd safe chair, vs a esd chair? When everything else is grounded. e.g I am wearing a ...
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### Can the axis of rotation of a celestial body point in any arbitrary direction?

I am developing a small computer program that involves moderately simple simulation of elliptical Kepler orbits for fictional, generated star systems. I'm doing this without much prior knowledge of ...