Law Definition and 999 Threads

I'm preparing for exam but it seems I can't find problems similar to this on the internet. Here I will apply Gauss's law on the electric field vector to get the charge density. but the problem is that I can't find similar examples on the internet that uses direct vectors on Maxwell's equations...

So I have a trolley of mass m that moves on a straight line. A sphere of mass m, is attached on the trolley with a light string of length a and it is left to oscillate. Just to give some idea of their positions: r_trolley = xi r_sphere = (x-asinθ)i - acosθj (θ is the angle between the string...

A direct current in the primary winding results in a constant magnetic field going through the center of the coil. If we have a magnetic core and a second winding, why doesn't the magnetic flux going through the core result in a current in the secondary coil, as well, according to Ampere's law?

Hello, I wonder if you could give me some advice to how solve this question. What I was thinking to solve it was to determine J by using Ohms law, ## \vec J = \sigma_{\alpha} \vec E ## I already determined the E field for for the sphere, I got it from a) ("a)" was to determined all the bound...

I often see this set up in thermodynamic problems and need clarification on how Newton's Laws are involved for the piston: Gas inside a piston cylinder (1) is heated expanding the gas and raising the piston (initially at rest) to a height (2) in a constant pressure quasi-equilibrium process...

Forces: Box--> W(weight) and T(tension) Rope-->T1(reaction of T) and T2(because of the helicopter) So first i calculated Weight: W=mg=400*10=4000N In order to find the acceleration i should use Newton's 2nd law so: (Box) : T - W = ma T - 4000=400a The problem is with the rope...

When trying to explain from where did all the laws come from, John Wheeler proposed the anaphorism of "Law without law". He proposed that at the "beginning" there were no laws whatsoever, only pure chaos, and that they emerged from randomness and chaos when our universe was created. In his own...

I need help finding the resultant with vectors: 37.5N[NE] and 45N[21° S of E] I just don't know a way to find the angles within this triangle to help me get the resultant, so can anybody help me out?

eg. For a ball in free fall (ignoring air resistance) there is only one force acting if the system is just considered to be the ball. It seems necessary to go to the system which includes the Earth for identification of the reaction force to be made. Is there any rule for how big a system must...

Hey everyone, I've read in an article that Newton's 3rd law proves that there is no ether in space. It says, according to Newton's 3rd law, the mass of the space between objects should be 0; then, ether does not actually exist. Could you please explain to me why Newton's 3rd law imply that the...

I'm not sure if my answer is correct but I think the answer is false. Thank you for your help :) -sun1108

Is Newton's first law of motion applicable when walking?

Gauss law relates the net flux phi of an electric field through a closed surface to the net charge q that is enclosed by that surface. It tells us that Phi = q/permittivity Can I say it like this : The gauss law states that the net flux of the surface depends upon the net charge enclosed by that...

There are two questions in the photo. I have attempted the solution (attached below) and I would be highly obliged if someone would verify the same. Edit- Sorry the images of the solution have uploaded in the wrong order. 5th and 1st Image comprise of both parts of Q1 while the remaining of Q2.

In a binary elliptical/circular orbit, the R^3 refers to the distance between the 2 planets. In the picture below, ##T^2 = kr^3##. However, for an elliptical orbit about the sun (which is assumed to be fixed as it is so heavy), and where the sun is located at a focus of the ellipse, ##T^2 =...

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My book claims that the diff. form of Gauss' law is $$\nabla\cdot\mathbf E=4\pi\rho$$ Can someone tell me why it isn't ##\nabla\cdot\mathbf E=\rho/\epsilon_0##?

For the first part, I have expressed it in the following differential form- dU= delta (Q) + BdM Now for the second part I am having major confusion. I know that B corresponds to P and M corresponds to V as generalised force and generalised displacement respectively for a Paramagnetic substance...

I am speaking here not of the modern definitions (like a 1st Newton law as a definition of an inertial reference frame), but rather on the way the 1st law was formulated in the time of Newton. That is, it's obvious that the 1st Newton law in its original formulation is a corollary of the 2nd...

I realized I never actually derived the kinematic equations of motion for the exact Newtonian gravitational force. For an object falling near the surface of the earth, how do we handle integrating the equation of motion to derive the kinematics equations without using the approximation of...

(a) Due to Coulomb's law all charges whether internal or external to Gaussian surface will contribute to the electric field. This is also mentioned as it's correct answer. (b) The answer is "equal to", which makes no sense to me. It could be greater than, equal to, or less than that obtained...

Dear colleagues, I am dealing with rope friction and the so-called Capstan equation. Situation: A rope wraps around a cylinder with a wrap angle. It depends on the input force. There are very comprehensive approaches by other colleagues, where the friction value depends on the normal force or...

(I accidentally missed my lesson and I don't know how to apply this question to the formula)

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I tried just calculating the force with Coulomb's law, then calculating the forces for each vector individually and adding, but I got it wrong both ways

So I am a fan of astronomy, cosmology and astrophysics from a FAR. The math is way beyond my abilities but I like to just sometimes read and think about the very small parts I am able to comprehend. So my hats off to all of you that are able to fully enjoy this stuff, you're very lucky...

I have heard from a knowledgeable physics proffessor, time exists independently and it is not a consequence of arrow of time. Could some body explain this?

(I haven't been actively following this line of research... but I think it is possibly interesting reading. It's been in the science news today.) "Black Hole Area Law Tested" (synopsis) https://physics.aps.org/articles/v14/s87 "Testing the Black-Hole Area Law with GW150914" Maximiliano Isi...

I've calculated the negative time derivative of B(r, t) as: $$-\frac{\partial B}{\partial t} = k~\text x~E_0~\text{sin}(k \cdot r - \omega t + \phi)$$ The cross product can be easily expanded, I'd just rather not do the LaTeX for if I can avoid it. The Curl of the electric field...

I investigated the flow rate of differing dilutions of glycerol through an orifice of a vertical tube and obtained the following: I'm looking for a way to quantify these results so looked to Poiseuille's Law; I'm pretty sure my graph does not show inverse proportion? Could anyone advise me as...

I'm confused by which forces should be equal to each other and what I solve for. How should I approach this problem?

I just want to know if this proof is okay, and I would like advise on how to improve it. Proof: i. Proving that ∠BAC ⩭∠BDC: Let gamma be the circumscribed circle of ABC. Let D be the point on gamma such that DB is a diameter of gamma. The sum of the angles within a triangle equal to 180°. Adding...

∫c Edl =-d/dt∫sBda

Does the law of conservation of mass fail to meet the first postulate of the special theory of relativity(the laws of physics are the same in all inertial frames of reference)?

Hello fellow physicists, I need to prove that when ##\omega << \omega_0##, Lorentz equation for refractive indexes: ##n^2(\omega) = 1 + \frac {\omega^2_p} {\omega^2_0 - \omega^2}## turns into Cauchy's empirical law: ##n(\lambda)=A+\frac B {\lambda^2}## I also need to express A and B as a...

I am reading Planck 2015 results. In particular, I focused on "Power law potentials" subsection. The issues I have are 1. I do not understand why the validity of the model can be determined by the value of the ##B## mode. 2. Why the ##B## mode values ##\ln B = −11.6## and ##\ln B = −23.3## for...

I have attached an image showing the perimeters of the problem. I have included what I think is the solution, could someone please take a look and tell me if I am on the correct path, in the solution I am taking Joules as a common term to attempt to solve the question. The gas I have used is N...

Why is this equation: B(D - d)/mu + Bd = mu0 N I true? B = magnetic field in the hole of the toroid D = Average diameter of the toroid d = Diameter of hole of toroid mu = relative permeability of iron, or whatever the toroid is made of mu0 = 4pi x 10^-7 N = Number of turns on the toroid I =...

'Every non-equilibrium state of a system or local subsystem for which entropy is well defined must be equipped with a metric in state space with respect to which the irreversible component of its time evolution is in the direction of steepest entropy ascent compatible with the conservation...

It is a long problem, but it is simple to understand. I am having trouble with part A. My attempt: Pressure outside > pressure inside container. pV = constant (isothermal). At equilibrium, all gases are at atmospheric pressure. Because it is quasi-static, the pressures of both compartments are...

In classical physics, we treat an electron as a point charge with a Coulomb potential ## V = \frac{q}{4\pi\epsilon_o r}##. However, in quantum mechanics, we treat it as an electron cloud. In this situation, how shall we describe the Coulomb potential? Shall we treat the electron as a charge...

Hi, I was wondering, if the charges do not move in a non inertial frame and I don't move too in this frame, will I see the same Coulomb force, some fictitious forces and radiation coming from these static charges? Thanks!

Hey all. This is about Ohm's Law (and specifically resistance). When you plot the change in current vs the change in voltage you should get a linear trend line (providing it is from an ohmic device). The gradient should be the resistance. My questions is why does the gradient value need to be...

Given u(t) = (u_0 - T)e^(kt) + T, find the limit of u(t) as t tends to 0 from the right side. The answer is u_0. How is the answer found? Seeking a hint or two. Can this Law of Cooling be graphed? If so, what does the graph look like?

Given u(t) = (u_0 - T)e^(kt) + T, find the limit of u(t) as t tends to positive infinity. The answer is T. How is the answer found? Seeking a hint or two.

[url="https://www.physicsforums.com/insights/tolman-law-in-a-nutshell/"]Continue reading...

Hi. How does the charge ##q## relate to the charges ##q_1, q_2## (see equations). For example, if ##q_1## is an electron and ##q_2## is a proton, is ##q## just a product or sum or something else of the two? Also, in Columb's law, how would I conceptualize charges ##q_1, q_2## in a system of a...

As we know that the magnetic induction causes an electric current in a wire and Faraday has formulated his Electromotive equation ##\epsilon=-\frac{d\Phi}{dt}##. And then Maxwell-Faraday's equation is: ##\nabla \times E=-\frac{\partial B}{\partial t}##, until now this was just an introduction...