Law Definition and 999 Threads

I know that Ienl for the inner cylinder is just I and the current density for the outer tube is J1= -I/(pi(Ra^2-Rb^2). I assume that the current through the enclosed portion of the conducting tube (I1) is equal to J1(A1) where A1 is the area of the enclosed portion of the conducting tube. I...

Newton's gravity depends on the euclidean distance between two masses. Two comoving frames will have different values of length between masses so the forces will be different in two frames. Is it enough to prove that the gravity rule has to be modified?

I was able to solve this question successfully by utilizing the sine and cosine law however my instructor said I was only allowed to utilize the vector component method, I am unsure how to complete this question using the vector component method as we have two unknowns(those being the angle of...

F = -F

I know the Gauss law for surface integral to calculate total charge by integrating the normal components of electric field around whole surface . but in above expression charge is calculated using line integration of normal components of electric field along line. i don't understand this...

"Reversibility means that we never lose information, that at a fundamental level we can always retrodict the past as well as predict the future in the laws of physics". Susskind in his Theoretical minimum Lecture 2 describes about the laws which are true and which are not. He tells the law of...

I solved laplacian equation. and got the solution of V(r, phi) = a. +b.lnr + (summation) an r^n sin(n phi +alpha n ) + (summation) bn r ^-n sin( n phi +beta n)

Newton arrived at "there is a force that drives a planet around the star by examining kepler's laws but how did he arrive to inverse square law by kepler's third law (##T^2=\frac {4\pi r^3}{GM}##)? Thank you.

Here, it's shown how white light, after passing from air to another medium, gets broken down into its constituent coloured rays. Each has its own refractive index in the medium, but it's only shown here red, blue and yellow. The auther comments on this image and says that, for small angles of...

First of all, Is ##\beta## given by the Planck's law of black-body is the amount of power contained in radiation emitted by a black body? I'm not sure to fully understand the law above. Does it means that if amount of power over all the frequencies is greater than the energy needed to remove an...

Where do the laws of reflection, refraction, and Snell's law come from in geometric optics? Are they derivable from basic laws of physics?

regarding the last question. I know that resistance is a negative force because it goes in the opposite direction to the movement of the boat. So whenever, I want to apply Newton's 2nd law of motion: the sum of forces = m a I should write - F resit = m.a. However, they have considered the...

Hi; I understand Kepler 3 in terms of the relationship that it demonstrates. I have researched the internet but can't find a reason why this relationship exists. Is it somehow a consequence of some type of gravitational balance, if not is there some other mechanical reason? Thanks Martyn

Summary: Trying to understand the relationship between gravity, thermodynamics and entropy, thank you. Gravity can take a diffuse cloud of gas filling a given volume of space at equilibrium density and temperature, and turn it into a burning star surrounded by empty space. Does this mean that...

I've attached what I have so far. Used Gauss's law, everything seemed to make sense except the units don't work out in the end. The charge density function if given by: r(z)=az, where z is the perpendicular distance inside the plane.

I can’t quite work my head around this question, I am having a difficult time analyzing the question, I can’t seem to make out what the initial and final conditions are would appreciate all the help I could get cheers

Consider a closed path consisting of a loop of wire with a nonconducting gap that completes the closed path. The wire is threaded through a toroidal permanent magnet, magnetized around the toroid (what I call a stealth magnet). The magnetic flux is considered to be confined to the magnet. The...

I'm trying to understand this paper (equation 2.16 specifically): Bini, D., Carini, P., & Jantzen, R. T. (1995). Relative observer kinematics in general relativity. Classical and Quantum Gravity. Am I correct in reading there is no way to express the relativistic relative velocity composition...

AIUI, this is the current level of micro-ization of computer chips. I had always thought that eventually quantum effects start to become an issue when the transistors get to within 20 atoms in distance, which it would seem that 2 nm is.

$$F=G\frac{m_1 m_2}{r^2}$$ is presumably for point masses. If the masses weren't a point masses, then wouldn't you need a version of the formula that sums up the gravity for each infinitesimal portion of the masses? And for my money, "summing up" in physics is integrals, right? So would it be...

I'm sure this gets asked a lot. CPUs and GPUs still kind of mystify me, since I do not know their science. It came to me after studying some computational linguistics that it might be possible that in the next 100 years, we might have smart-translating, smart-talking machines without a theory...

Many texts state that in an elliptic orbit you can find angular momentum magnitude as $$ L = r m v = m r^2 \frac {d \theta} {dt} $$ I wonder if $$ v = r \frac {d \theta} {dt} $$ is valid at every point. I understand this approximation in a circumference or radius r but what about an arc...

Does Ohm’s Law, V = IR work for light bulbs? It appears not to from my simple experiment below. In the figure below, I measured the resistance of a lightbulb and found that resistance to be 2.6 ohms. However, when I connect this lightbulb into the circuit where I measure the voltage across...

A ship that moves at a speed very close to light, its relative mass increases and may be comparable to the mass of the planets or the sun, in this case it can change the orbit of the planets and the sun (according to the law of gravity of two bodies) Is this analysis correct?

Hello, I need help with making sure I am using instrumentation error analysis correctly through an experiment in which I verify Ohm’s Law for a simple circuit. I do have a few questions below. I calculated and measured the error two different ways and did not get the same error by both methods...

Hello What experiment or observation shows that for atoms, molecules or masses of gas, there is attraction in the sense of Newton's law (universal attraction)? Bernadette

Something about Newton's third law confuses me, when I hold my phone and I move it around it's velocity is changing, therefore because Newton's first law it's acted on by a force, and because Newton's second law, the force is directly proportional to the mass and acceleration of that object...

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Summary: TL;DR: Doing an assignment in which we are to apply Dalton's Law to a product to improve/ better it OR create a completely new product using the law. Let your creativity run wild! Hi there! I am doing an assignment in which we are to apply Dalton's Law to a product to improve/ better...

This problem is from Griffiths' book Introduction to Electrodynamics [Problem 2.53 in 4th edition]. It considers that electrons are emitted from the cathode and move to the anode. This establishes a constant current between the parallel plates. It asks to show that the constant current ##I##...

Hi, here's a theoretical problem that I am trying to find a satisfactory answer for. Imagine a coil that is temporarily switched on an off and generates a magnetic field that permeates through space. Now imagine a charged particle passing through this field, at time that the coil is already...

Hi there. I have a problem solving above problem. How can I move on with my solution? It seems to me that I have proper approach but I'm just stuck with the energy equation ;/ Part of solution below:

Imagine a long deformable rod which has just been hammered on the top end (the bottom end is clamped to Earth). Consider a time interval $dt = t_{2} - t_{1}$ in which the pressure wave is traveling somewhere within the length of the rod (meaning some portion of the object has already "felt" the...

If I've steady currents i.e ##\frac{\partial}{\partial t} J=0## , does coulombs law hold in this case to find the electric field? Since this isn't the case of electrostatics so it might not hold, but if we look at the charge density it is the same for all time, this suggests that the charges...

Hi Pfs, There are different kinds of entropies. I discoved the free entropy. https://arxiv.org/pdf/math/0304341.pdf the second law says that the total entropy cannot decrease when time goes by. Is it always the same "time" for the different entropies? the author, Voiculescu, wrote articles...

hello i have a question about kinetics : to have the integrated rate law for second order reaction the professor write the following why we don't write the rate like this : rate = -1/2(d[1]/dt) ? why we ignore the stoichiometric coefficient ?

Hello everyone, So, I was wondering, the Biot-savart show us a magnetic field created by a constant electric current. Initially I thought that an example would be biological systems with a nervous system that works on the basis of electrical discharges, but I don't think it's a valid example...

The car that accelerates must enter according to the equation below the external force, while such an external force does not seem to exist. The force of friction between the car and the road is in the opposite direction of motion ؟

i would like to understand why my answer is incorrect i don't know what I am doing wrong i would like for some help

I'm reading a website where they're doing a derivation. Within the derivation they write $$E(X_n | X_{n-1}) = X_{n-1} + f \implies E(X_n) = E(X_{n-1} ) + f$$. Evidently the implication stems from the law of iterated expectation, but I can't see how. If it helps, the question asked is "what is...

When I try to derive Gauss's law with a straight line of charge with density ##\lambda## through a cylindrical surface of length L and radius R, $$\vec E = \frac{\lambda*L}{4\pi\epsilon*r^2}$$ $$A = 2\pi*r*L$$ $$\vec E*A = \frac{\lambda *L^2}{2\epsilon*r} \neq \frac{q_{enc}}{\epsilon}$$ What am...

Hello everyone. I use Bio Savar's law to determine the intensity of the magnetic induction vector. I use this formula R is distance of wire from point in which I calculate intensity of the magnetic induction. How can I known which angle is positive and which angle is negative from this two...

If a conductor moving through a magnetic field generates an emf, which it does, COULD a highly conductive liquid (eg: sea water) moving through said field (like a magnetic flowmeter measuring flow rate is used) generate and would it be enough to be useful?

α=30°; l=0.5 m; n1=1; n2=1.33 α+β=90°, so β=90°-30°=60°. Using Snell's law: sinβ/sinγ = n2/n1 sinγ≈0.651 γ≈41°. β=γ+θ (vertical angles) θ=60°-41°=19° tan(θ+β)=l/h h=l/tan(θ+γ) h=0.5/(tan(19+41))≈0.289 m

Einstein famously said “{Thermodynamics} is the only physical theory of universal content, which I am convinced, that within the framework of applicability of its basic concepts will never be overthrown.” I don't think any of us want to argue with Einstein, but it's worth noting the "within the...

Summary:: Figure b also shows that there is no negative sign in Faraday's Law. How do I know when to include the negative sign?

I am so embarrassed that I have forgotten so much of my physics and I am at the point of being away from school too long to remember even the most basics (Mom said no one can ever rob your education but I'm living proof otherwise). So please forgive my inability to discuss this at an academic...

Ok, so I understand how to find dphi/dt that is integral of -d/dt(B "dot" da). In this case I find a Phi that is a constant in space in time which causes me confusion in next step. Edit: dphi/dt is constant... Grithff's then says E field same as a Mag field above center of circular current. He...

I have gathered that forces always occur in pairs and are equal in magnitude but opposite in direction and that according to the second law a force is the product of the mas and acceleration of the object exerting the force. My problem is with getting this make sense with real life examples. If...