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Q&A

General Q&A about physics of any type and at any level

33%
+0 −2
To what extent does blender speed dissolve table salt + cold tap water?

At home daily, I need to mix my table salt + COLD tap water. As "Marine salts dissolve faster and more thoroughly when added to circulating water," I "use a powerhead to speed up mixing time — my V...

1 answer  ·  posted 8d ago by TextKit‭  ·  last activity 7d ago by Olin Lathrop‭

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+2 −0
Magnetization as a function of temperature in ferromagnets

Suppose a ferromagnetic material with initial magnetization $M_o$.Is there some specific formula which calculates the total magnetization $M$ as a function of $M_{o}$ and the Curie temperature $T_{...

0 answers  ·  posted 2mo ago by MissMulan‭

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+1 −0
Direction of vector of electric field

Suppose we have a arc of charges with some charge density $\lambda(\theta) = sin\theta$.I am using polar coordinates for convenience.But how can I find the direction of the unit vector of the net e...

0 answers  ·  posted 3mo ago by MissMulan‭  ·  edited 3mo ago by samcarter‭

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How can I easily UNcouple this slide and lock, on office chair? [closed]

I need to separate these two parts, the opposite of the GIF below. While my hunky husband was lifting the chair up, and my brawny brother pushing the frame down, I kept hitting the top of the slid...

0 answers  ·  posted 4mo ago by Este‭  ·  closed 4mo ago by Monica Cellio‭

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+1 −0
Maxwell equations EM wave confusion

The general formula for a EM wave (solving for the E field) is: where $\varepsilon = \varepsilon _{r}+j\frac{\sigma }{\omega }$ My professor told me that the conductivity of vacuum is 0 so we...

0 answers  ·  posted 4mo ago by MissMulan‭

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What are the efficient methods to vacuum or pump air into 15 meters underwater?

Say we have a four underwater components tidal power / hydro power system. Component A. A propeller would always orient along the same direction regardless the direction of the flow. This is th...

0 answers  ·  posted 5mo ago by HolyDamn2.0‭  ·  edited 4mo ago by HolyDamn2.0‭

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Is this a physics discussion or new energy? [closed]

Part 1 Say we have a round water pool, the radius is 10m, and the water depth is 2m. C is a fixed point: Fixed on the surface of water. Fixed at the center of the pool. F1 is stable forc...

2 answers  ·  posted 5mo ago by HolyDamn2.0‭  ·  last activity 4mo ago by Mithical‭

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If you're stopped and about to be hit from behind, should you brake or release the brake?

The title is a framing for a theoretical question; I'm not asking for practical advice. A friend was recently in this situation and my attempts to apply what I remember of a couple semesters of co...

1 answer  ·  posted 5mo ago by Monica Cellio‭  ·  last activity 5mo ago by Olin Lathrop‭

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How exactly do eddy currents slow down objects moving though a magnetic field

When a pendulum made of a conducting material moves through a magnetic field, it's a well-established fact that it experiences a retarding force, thus slowing it down, however, I'm unable to unders...

1 answer  ·  posted 5mo ago by esrdtfghjk‭  ·  last activity 5mo ago by Olin Lathrop‭

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maxwell equation in 1d

Maxwell's first law in differential form states that $$ \triangledown \cdot E = \frac{\rho}{\epsilon_{o}} $$ . In case of 1d can we say that $$\rho = \lambda$$ where $$\lambda$$ is the linear char...

1 answer  ·  posted 6mo ago by MissMulan‭  ·  last activity 4mo ago by celtschk‭

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Double slit experiment with 2 electrons fired from a gun

Suppose we perform the double slit experiment , but we fire instead 2 electrons instead of 1. In the double slit experiment performed in the 1920s a interference pattern was observed at the screen...

0 answers  ·  posted 6mo ago by MissMulan‭

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SI Units of wavefunction

What are the SI units of the wavefunction Ψ(x).I know that [Ψ(x)]^2 describes the probabilty of finding a quantum object at a certain quantum state but what about the wavefunction instead?

0 answers  ·  posted 6mo ago by MissMulan‭  ·  edited 6mo ago by MissMulan‭

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Differential equation solution cannot describe what happens in reality

Suppose we have a free falling object inside a planet's gravitational field with strength g.The planet's atmosphere provides a drag force which is dependant from the u^2 of the particle. Suppose t...

0 answers  ·  posted 6mo ago by MissMulan‭  ·  edited 6mo ago by MissMulan‭

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Classical Uncertainty

Suppose we are using a force gauge to measure gravity in a planet. We set the gauge force to the 1N range which has a resolution of .01 N. From its specs the error introduced during the measurmen...

0 answers  ·  posted 6mo ago by MissMulan‭

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System of ODEs models in physics

What examples of a system can be described by a system of ordinary differential equations?

1 answer  ·  posted 6mo ago by MissMulan‭  ·  last activity 6mo ago by Olin Lathrop‭

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How are charges sorted?

Im designing a capacitor and I have decided to make the surface of 1 plate of the capacitor bigger than the other plate. How are the charges sorted through A2?Are they spread out to cover all th...

0 answers  ·  posted 6mo ago by MissMulan‭

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Calculate inductance using laws of electromagnetism

Get 2 conductors and seperate them we can use Gauss's law to calculate the capacitance created by the seperation of the 2 conductors.Can we use other laws of electromagnetism to calculate the induc...

2 answers  ·  posted 7mo ago by MissMulan‭  ·  last activity 6mo ago by TonyStewart‭

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Meaning of complex frequency [closed]

If we have a LC high pass filter the transfer function H(s) becomes: $$ H(s) = \cfrac{sL}{sL + \cfrac{1}{sC}} $$ If we solve for s to find a pole of the transfer function we get: $$ s = j \cfrac...

0 answers  ·  posted 7mo ago by MissMulan‭  ·  closed 7mo ago by MissMulan‭

25%
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Why can these Single Vision lenses slow myopia for kids, but not adults? [closed]

These WorldFamous companies advertise that their lenses can control myopia for kids, NOT adults. But none of these lenses are approved by FDA. I asked my optometrist why merely kids, not adults. Bu...

1 answer  ·  posted 7mo ago by TextKit‭  ·  closed 7mo ago by Mithical‭

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Optically, why are circular eyeglasses lenses better than rectangular?

My optometrist said that round eyeglass lenses are OPTICALLY better than rectangular, particularly to correct myopia. He was NOT referring to fashion or style. I couldn't understand his explanatio...

1 answer  ·  posted 8mo ago by TextKit‭  ·  edited 7mo ago by TextKit‭

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Time dilation with current or very near technology of the next 100 years

With time dilation a cosmonaut could travel forth in time, especially in light speed. But are there much lesser speeds which might be achievable by humans in the next 100 years which could also in...

0 answers  ·  posted 9mo ago by deleted user

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Why can someone observe light, even when the light fails to illume that someone?

I never grokked the optics behind LightHouses and the WW2 poster below work. LightHouse beams are narrow and focussed. Doubtless, the light source can fail to illumine a seafarer or the enemy subm...

1 answer  ·  posted 10mo ago by TextKit‭  ·  last activity 10mo ago by Olin Lathrop‭

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Why do markers reflect light, even when the light source fails to illumine the space between the source and markers?

Please see below screenshot of 15:59.The LED spot light (fastened to the front of the boat) illumines merely a few meters in front, and fails to illumine most of the water between the boat and the...

1 answer  ·  posted 10mo ago by TextKit‭  ·  last activity 10mo ago by Olin Lathrop‭

60%
+1 −0
Calculating Surface temperatures of a thermal insulator

I'm interested in knowing the surface temperature of both sides of a double-pane or triple-pane window. Given the R-value of the window, and the air temps outside and inside, how can I calculate t...

1 answer  ·  posted 1y ago by re89j‭  ·  last activity 1y ago by Olin Lathrop‭

66%
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Calculating Max humidity for a house

I want to write some code to control my whole house humidifier. I want my code to calculate the percentile relative humidity above which dew will form on my windows. I have sensors for air tempera...

0 answers  ·  posted 1y ago by re89j‭

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Book suggestion on classical thermodynamics

I was looking for book on classical thermodynamics. I found lot of related posts in PSE but couldn't find a book which type I was expecting. I was searching for book which covers the whole thermody...

0 answers  ·  posted 1y ago by deleted user  ·  edited 1y ago by deleted user

60%
+1 −0
Conductivity with angle of light

In the lab I changed the angle the light hits a photoresistor and it doesnt obey Lambert's cosine law the conductivity of the photoresistor drops fast from +-20 to +-30 degrees angle.Why?

1 answer  ·  posted 1y ago by MissMulan‭  ·  last activity 1y ago by Olin Lathrop‭

75%
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How are the assumptions behind two ways of deriving the Rayleigh-Jeans law related?

The Rayleigh-Jeans law does a good job of describing the spectral radiance of a black body at low frequencies: $$B_{\nu}(T)=\frac{2kT\nu^2}{c^2}$$ with $T$ the temperature and $\nu$ the frequency...

1 answer  ·  posted 1y ago by HDE 226868‭  ·  last activity 1y ago by Derek Elkins‭

60%
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May it be that there are more than 8/9 planets in our solar system?

May it be that there are more than 8/9 planets in our solar system which aren't detectable with the current technologies? Is there any theory suggesting that our solar system has more planets, all...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Canina‭

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Is that electron which jumps from one stationary state to another?

In classical physics book of kleppner, i read that An atom can "jump" from one stationary state a to a lower b by emitting radiation with $E_a-E_b$. The frequency of the emitted "package of radi...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Olin Lathrop‭

71%
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Why series springs behave like parallel? A comparison between parallel resistance and series spring.

I know that equation for parallel resistance is $$\frac{1}{r_{tot}}=\sum_i \frac{1}{r_i}$$ But i wonder to see equation of series spring constant. If we add multiple spring in series. Then their ...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Olin Lathrop‭

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How electric displacement is proportional to surface charge?

$$\begin{alignat}{2} &amp;&amp; \vec \nabla \cdot \vec D &amp; = \rho_f \\ &amp; \implies &amp;\int_V \vec{\nabla} \cdot \vec D \mathrm d\tau &amp; = \int_V \rho_f\ \mathrm d \tau \\ &amp; \impl...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by deleted user

66%
+2 −0
What's the meaning of "outdated" in physics?

I was recently reading some questions here and there saying that "relativistic mass is outdated". I saw someone saying that "outdated" doesn't mean the concept is wrong. My question is what physici...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Mithrandir24601‭

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What's the equation of kinetic energy of charged particle?

I was looking for equation of motion. I came up with a solution but it doesn't satisfy me. Cause I was trying to find motion of that particle using Lagrangian. We know that $$W=\int \vec F\cdot d\...

1 answer  ·  posted 1y ago by deleted user  ·  edited 11mo ago by deleted user

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Are lamps, with blistering light bulbs exposed and facing down on the user, dangersome?

IKEA discontinued this NOVEMBER lamp in 2007, but I still use it. IKEA confirmed that they did not intend or design any cover or share with this lamp, and the light bulb is supposed to be exposed. ...

2 answers  ·  posted 1y ago by TextKit‭  ·  last activity 1y ago by celtschk‭

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How can the kinetic energy equation be intuitively understood?

Momentum is proportional to an object's velocity, and kinetic energy is proportional to the square of its velocity $\dfrac{mv^2}{2}$. It's pretty intuitive that if object B is going twice as fast a...

3 answers  ·  posted 1y ago by gmcgath‭  ·  last activity 1y ago by celtschk‭

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Is $E=mc^2$ true for all frame of references?

Which one is correct? $$E=mc^2$$ or $$E^2=(mc^2)^2+(pc)^2$$ I mostly seen $$E=mc^2$$ from my childhood, and when I was learning problem solving in relativistic mechanics I had seen $$E^2=(mc^2)^2...

1 answer  ·  posted 1y ago by deleted user  ·  edited 12mo ago by deleted user

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Clear up confusion on Minkowski signature

All given metrics are for orthonormal-basis. 2 dimensional spacetime : I saw that Minkowski Metric looks like this : $$\pmatrix{-1 &amp; 0 \\ 0 &amp; 1}$$ or $$\pmatrix{1 &amp; 0 \\ 0 &amp; -1}...

1 answer  ·  posted 1y ago by deleted user  ·  edited 1y ago by deleted user

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Are there areas in the observable universe which surely cannot support life as we know them?

Are there areas in the observable universe which surely cannot contain galaxies with planets that can support life as we know them?

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Olin Lathrop‭

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What is $\mathcal{O}$ in integration of potential?

I saw following equation in Griffiths EM $$V(r)=-\int_\mathcal{O}^r \vec E \cdot d\vec l$$ While the surface was closed but not symmetrical circular. At first I was thinking $\mathcal O$ was repr...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by deleted user

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Why did my roller luggage's wheels stop turning smoothly?

Two weeks ago, my carry on worked perfectly. But last week the detachable wheels stopped rotating smoothly, when I tried to glide my carry on. The wheels budge JUST A TAD when you push them hard, b...

0 answers  ·  posted 1y ago by TextKit‭  ·  last activity 1y ago by deleted user

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Calculate Center of Thrust

If I have a rocket with some known number of engines $n$, each producing thrust with arbitrary direction $T_n$ and center of thrust $r_n$, the total thrust amount and direction $T_{total}$ is equal...

1 answer  ·  posted 1y ago by Josh Hyatt‭  ·  last activity 1y ago by Olin Lathrop‭

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What does Laplace operator represent?

I was wondering what's the physical meaning of Laplace operator. $\vec\nabla$ actually represent a field. I had seen that Laplace operator is written as $\vec \nabla \cdot \vec\nabla=\nabla^2=\Delt...

1 answer  ·  posted 1y ago by deleted user  ·  last activity 1y ago by deleted user

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What is "order" and "disorder" in entropy?

What is "disorder" in entropy? Entropy is measurement of "disorder". (Some says it's not "disorder") I had read "disorder" and "order" of entropy in my book. But I was wondering what "order" ...

2 answers  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Derek Elkins‭

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Should I always write units in equation no matter if it looks like variable?

I am not sure if it is suitable in the site. I am asking the question here cause Olin and Celtschk said it here. They told me to use unit in every "single line" (Nope! They didn't say like it. Oli...

2 answers  ·  posted 1y ago by deleted user  ·  last activity 1y ago by Canina‭

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What is Ether theory? (I think the book I read is misinterpreting Ether)

I was reading about Ether, Maxwell and Young-double-slit experiment. I got a question about Ether law. Let me say what I read about Ether Law. Suppose, a boat is traveling with Adverse of Water ...

2 answers  ·  posted 1y ago by A person who doesn't know anything‭  ·  edited 1y ago by A person who doesn't know anything‭

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Is it possible to derive the Dieterici equation starting from assumptions about microstates?

I was introduced to a somewhat novel derivation of the ideal gas law that starts by thinking about the number of microstates of an ideal gas, $\Omega$. Say we have a gas with a single particle in a...

0 answers  ·  posted 1y ago by HDE 226868‭

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What is Apsidal Vector?

I have recently heard of Apsidal Vectors. I was searching about it through internet. I had found the video in YT. I had found similar question in PF. But, the PF answer wasn't clear to me. I am jus...

0 answers  ·  posted 1y ago by Anonymous‭

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What's the importance of Poisson brackets?

$$F=F(q,p,t)$$ $$\frac{dF}{dt}=\frac{\partial F}{\partial q}\frac{\partial q}{\partial t}+\frac{\partial F}{\partial p}\frac{\partial p}{\partial t}+\frac{\partial F}{\partial t}$$ $$=\frac{\part...

0 answers  ·  posted 1y ago by deleted user  ·  edited 1y ago by deleted user

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What is semiholonomic?

What is semiholonomic is? Holonomic actually means two point can be expressed by a equation. Non-holonomic can be expressed but, not properly. Holonomic e.g. $r^2-a^2=0$ Non-holonomic e.g. $r^2-a...

1 answer  ·  posted 1y ago by Anonymous‭  ·  last activity 1y ago by HDE 226868‭

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