Why can't we see around corners?
Why can't we see around corners? Or perhaps the right question should be: Why can we see anything at all other than blurred light where no shapes can be distinguished? If we use a wave theory of light,...
View ArticleProblems of F = dp/dt
A box which carries sand is moving with a constant velocity u on a smooth horizontal surface. The sand is removed during the motion of the box such that the sand has the same horizontal velocity u. We...
View Articlegravitational field strength of the earth
Hi, Using the formula g = [itex]\frac{GM}{r2}[/itex] I found 'g' to equal (9.792121683 x 106 [itex]\frac{N}{kg}[/itex]) The value of g is 9.8 [itex]\frac{N}{kg}[/itex]. I am wondering if I made an...
View ArticlePolarization question
A thick spherical shell (inner radius a, outer radius b) is made of dielectric materials with a "frozen-in"polarization P(r) =k/r rhat; where k is a constant and r is the distance from the centre....
View ArticleHow to arrive at Lorentz gauge condition?
http://en.wikipedia.org/wiki/Lorenz_gauge_condition I know it's used to simplify the 2 partial differential equations of the potentials, but why can we put such a restriction on the potentials? Doesn't...
View ArticleHow to explain the physics of phase lag due to viscosity damping in forced...
Dear all, Can anyone explain the the phase lag between force and displacement in single degree of freedom forced vibration with viscosity damping? The response of phase angle derived by mechanical...
View ArticleHow is charge/mass ratio derived in this example?!?!
Hello, I know there are many ways to derive an expression for "q/m", but I am having some troubles with this one. We are given: (1/2)mv^2 = qV (mass, velocity, charge, voltage) qvB = (mv^2) / r...
View ArticleAngular acceleration in terms of angular velocity
I've been working on problems that deal with pendulums and I've noticed that a few of my answers require me to find the angular velocity, frequency, period of a pendulum. I managed to get the answer...
View ArticleDoppler effect
We can know about distant stars temperature,its elements etc by observing its spectra... But that star has a velocity related to us... The spectra will be shifted... Then how do we know the correct...
View ArticleLaboratory work, magnification
I am working with interference which pattern I want to magnify to a CCD. The question is how can I determine the magnification of the interference pattern to the CCD? An aperture lens is used. I know...
View ArticlePhysics problem
I shoot a bullet of mass m with velocity v against a block of mass M. Find how far the bullet penetrates the block. This problem turned up in my friends examination and I believe it can't be done...
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Electric field lines next to conductor
Dear Physics Forums readers Let a two dimensional rectangle R1 carry a surface charge [itex]\sigma[/itex] and be placed next to another rectangle R2 of the same shape made from metal (i.e. a...
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About: Magnetic force
Hi, I am trying to play around with magnets on my free time, I ordered some neodyum magnets and I've been thinking of making my own electromagnets, I had some of questions and I was hoping someone here...
View ArticleWhat happened to Ohm's law?
Earlier I asked for help about a high voltage power supply, and I was told not to worry too much about 20k volts because they have a very low current I was left thinking about that say whatever circuit...
View ArticleMagnetic force lost when you break a magnet?
if you have a magnet that pulls 40lbs of force if you broke that into 2 how much force will each magnet pull. i have some neodymium magnets from hardrives and i wanna break them up but i wanna know if...
View Articleelectromagnetic field in vertical
Hello, I know the electromagnetic field propagates in a 3D space so if I am horizontally aligned with the field I will receive its variation but what if I'm vertically aligned ? thanks
View ArticleCheck my work please: Jupiter as power station?
I'm developing a realistic sci-fi story in which power for the outer planets is produced from Jupiter's magnetic field. Now from Faraday's law I have V= N * A * (2*∏*RPM/60) B where N is the number of...
View Articleboundary condition problem for diffusion equation
BOUNDARY CONDITION PROBLEM I have came up with matrix for numerical solution for a problem where chemical is introduced to channel domain, concentration equation: δc/δt=D*((δ^2c)/(δx^2))-kc assuming...
View ArticleLegendre Expansion solution to sphere of potential V with charge q outside
Hi, It seems that there is no much examples of this particular case. OK, we all know how to write the general solution to Laplace equation in spherical coordinates in terms of Legendre polynomials...
View Articleconsidering enrolling in mechanics
I'm considering enrolling in mechanics (lagrange/hamilton etc.), and I've heard it's a very difficult course. In fact my advisor advised against me taking it since I have the prerequisites but not the...
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