The formula pV=1/3Nm(c_rms)^2 in non cuboids
Does [itex]pV = \dfrac 1 3 N m \left(c_{rms}\right)^2[/itex] apply in containers that aren't cuboids? The derivation I have seen uses a cuboid container so I'm not sure if or how this can be generalised.
View ArticleWork done by the Lorentz force?
When a wire is placed in a magnetic field and current flows in that wire work is done on the wire and be calculated: 1) W = Fd 2) F = IL x B 3) W = ( IL x B )x d Must there be any derivations beyond...
View ArticleEntropy concept
I'm having trouble getting my head around entropy. In an isolated system, entropy can only remain the same or increase. Is this the same for a thermodynamics cycle? What I mean is, if I drew a cycle on...
View ArticleShot noise in a photo diode
Not really sure where this belongs... But here goes: If you illuminate a photo diode it generates a current because electrons are being emitted from its cathode. Since each emission is however an...
View ArticleFocal Length of a Plano Convex Lens
Hi, The focal length of the Plano-Convex lens as calculated by the lens maker equation: Does it work when light crosses the lens from the convex side, planar side, or both? Thanks.
View ArticleHard sphere gas
Hi guys. Consider the problem of calculating the multiplicity (phase space volume) of N hard sphere gases each of whose center of mass is confined to a volume V. The spheres themselves have volume...
View Articletank depressurization through a valve
Hello guys, I want to study the temperature evolution of a gas in a vessel from 200 bar to 20 bar. I made the assumption the expansion is isentropic. However I have some trouble to represent the heat...
View ArticleExternal forces on rigid body
I'm having trouble with this line from Goldstein-"the center of mass moves as if the total external force were acting on the entire mass of the system concentrated at the center of mass." If a bar is...
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Derivation in classical mechanics
I'm studying classical mechanics and I'm stumbling in the quantity of differential identities. Being S the action, H the hamiltonian, L the lagrangian, T the kinetic energy and V the potential energy,...
View Articlecharacteristics of beam splitters
I read that there are polarizing and non polarizing beam splitters. Are there adjustable bleam splitters between them?
View ArticlePlanck's law derivation
The derivation of Planck's law in my textbook begins with the assumption that the energy of an oscillator with frequency ##\nu## is quantised in units of ##h\nu##. It follows that the average energy of...
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Problem with differential/integral definitions
If work ##W = \Delta E = \int_{s} \vec{F} \cdot d\vec{s}##, so work can't be ##\frac{dW}{d\vec{s}} = \vec{F}## like is here: http://en.wikipedia.org/wiki/Work_%2...ath_dependence cause this implies...
View ArticleVariation of gravitational force with calculus
Hi all, This is Newton's universal law of gravitation: F = GMm/r2, where r is the distance between the centre of the two bodies. Therefore, considering two objects in mutual gravitational acceleration,...
View ArticleMaking a 50 um collimated beam on a budget
Hello again, My handy optics engineer has left the country leaving me with a problem that's over my head. I need a low cost (i.e. $500.00) solution to produce a circular, collimated, 405nm beam. My...
View ArticleRLC changes negatively when is measured in the inverse sense?
If ##V_{BA} = P_B - P_A## (where V is the voltage and P the potential) so, ##V_{AB} = - V_{BA}##. The same ideia for the current: ##i_{BA} = - i_{AB}##, so this ideia of sense is true too for resistor,...
View ArticleWhy does the Pathagorean theorem work for forces?
Hey guys, I understand why the theorem describes the relationship between the lengths of the sides of a right triangle; but how do we know that the theorem works for forces? why is the hypotenuse the...
View ArticleFriction torque vs. contact area
I promise this isn't homework, it's actually for my research :-P Here goes: When two bodies are in contact and *translate* with respect to each other, there is no dependence of friction on contact...
View Articlecalculate the intensity
So I understand that to calculate the intensity a distance d away from a light-bulb you would treat the light-bulb as a point source and do a gaussian-sphere-type-of-thing to figure out the intensity...
View Articleabsorption of paper towel
Hello. I have a question. I have two glasses - one is full, one is empty. And I will take a long paper towel to them - the first end to full glass and the second end to empty glass to same height. A...
View ArticleCalculating deformation energy
Hi all, I've been trying to understand how to calculate the elastic energy of a deformed object. For example, if I have a box, and I push on it and it deforms, how can I calculate this deformation...
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