What is the state of matter beyond the critical point?
Starting from a gas state and reaching the liquid state by getting around the critical point in a p-T phase diagram, what happens (qualitatively) to the molecules (or atoms)? Does a fraction of them...
View ArticleCan we obtain a permanently polarized ice?
What is the result of the following experiment? We put an amount of water in a uniform electrostatic field. We get a polarisation. Keeping the polarizing field, we cool rapidly the water until it...
View ArticleI don't understand capacitance
Hello, So I am told that capacitance is a measure of how much charge can be stored in a capacitor. However, I don't have an intuitive understanding for why it is a relationship between charge and...
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Induced drag confusion - More than one cause?
Hi, I'm a bit confused by induced drag on an aerofoil and hoping somebody can clear it up for me. I understand that as air slips around the edges of the wing due to the pressure differential between...
View ArticleWhat's wrong with this derivation for rotational energy of a sphere?
First, energy of a disk: [tex] \int \frac{dm}{2}r^2 \omega^2 =\frac{\omega^2}{2}\int_0^R m\frac{2 \pi r dr}{\pi R^2}r^2 =\frac{m\omega^2}{ R^2}\int_0^R r^3 dr=\frac{m\omega^2 R^2}{4 }[/tex] Which...
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calculating torque with buyouant force and hardly definiable arm
Hej Guy, Here I am again with a question on torque basically. Please see the image below. I have a half tube underwater. The tube have air inside. Now I would like to calculate the torque for this...
View ArticleDegrees of freedom in crystal
It seems to me that there should only be three degrees of freedom for each atom in a crystal, one for each direction of vibration; but apparently there are six? Can someone explain? Thanks.
View ArticleThermodynamics - Q, U, W and H
I have understood that Q=heat absorbed, ΔU=energy change, ΔH=enthalpy change, W=work done by system = Δ(PV)+Wmech (where Wmech is mechanical work, P is pressure and V is volume). What I don't...
View ArticleExperiments Involving Lasers and Optics
Hello all, I need to design an experimental apparatus that involves manipulating the path of a laser. Thus far I only know the bare basics about optics and I have never attempted optical apparatus...
View ArticleChange in Gravity Affecting Free Fall
In high school physics, which I am in, we learn that to find the distance that and object falls can be found with the equation, x=v0t+1/2gt2. We also learn that the force of gravity between two objects...
View ArticleBoltzmann distribution for particle energy
I'm puzzled by the appearance in the literature of 2 conflicting forms: P(E)=√(E)*exp(-E), which I understand as derived from the Maxwell distribution for speed. It is a chi -square distribution with 3...
View Articlesurface tension
I was solving a problem from fluid mechanics... But that led me to question my conception abt surface tension... The problem stated that the max force needed to uphold a needle(ignore its weight)from...
View ArticleTemperature differences to create a strong pull
Dear physics forum, i'm currently working on a project and wondering what should the air temperature difference be to create a strong pulling force ? I'm working on creating a sustainable house, the...
View ArticleContinuity conditions in electrodynamics.
I have a question about the derivation of the boundary conditions at surfaces of electromagnetic fields. These conditions say, that the tangential component of the electric and the normal component of...
View ArticleHow to calculate power output in piezoelectric material?
Hi, I want to use piezoelectric material to harvest compression energy, i need to calculate the power output but i can't find enough information on the web to figure it out... First, I want to learn...
View ArticleWhy is there a correlation between gravitational and magnetic fields?
A gravitational field and a magnetic field both decrease in strength at the distance squared. They are two totally different forces so why the correlation?
View ArticleWhy electrolytes decompose so easily?
Why supercaps could withstand only 2-5 V before electrolyte starts to decompose? And solid electrolyte such as proton conductor could withstand no more than a few volts? Superionic conductors such as...
View ArticleIs there a special term for refractive indices when 1 is subtracted?
I have been doing a bit of studying for my optics course and I have often come across refractive indices or materials being presented as n-1 (which often makes a lot of sense). I was just wondering if...
View ArticleQuick question on Newton's third law & energy conservation
I have a quick question on Newton's third law. When a 100kg astronaut in space is holding a 100 kg rock and then pushes it away from him with 50 joules of energy (the kinetic energy put into the...
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Lagrangian mechanics - derivation doubt.
In the attached snip, the last few steps of the lagrangian equation is shown. I don't understand how the [itex]\frac{\delta V}{\delta\dot{q_j}}= 0[/itex]. As an example let me take gravitational force....
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