Law Definition and 999 Threads

Homework Statement Two small balls, each of mass 5.0 g, are attached to silk threads 50 cm long, which are in turn tied to the same point on the ceiling, as shown below. When the balls are given the same charge Q, the threads hang at 5.0° to the vertical, as shown below. What is the magnitude...

If I have a magnetic field describing a closed path it means that this closed path is surrounding a current, right? But if I have no current, is it the displacement current ? I'm thinking of a magnetic dipole, its magnetic field describes closed paths from its north to south pole, so is there a...

Hello, I'm new to the language of calculus. I am learning about Newtons second law and I'm trying to understand it's forms in calculus. Excuse my notation, just trying to keep it as simple as possible. F=m * dV/dt I know V= dx/dt My textbook says you can 'apply chain rule' to obtain the...

Homework Statement Consider a cylindrical parcel of air of area A and infinitesimal height dz. If this air parcel is to remain stationary, the difference between the total pressure forces exerted on its top and bottom faces must be equal to its weight. Use this information and the ideal gas...

Homework Statement The two components of a double star are observed to move in circles of radii ##r_1## and ##r_2##. What is the ratio of their masses? (Hint: Write down their accelerations in terms of the angular velocity of rotation ##\omega##) Homework Equations ##m\ddot{\vec{x}}=...

Geiger–Nuttall rule relates the decay constant of a radioactive isotope with the energy of the alpha particles emitted. Roughly speaking, it states that short-lived isotopes emit more energetic alpha particles than long-lived ones. - wiki I am trying to understand why there is an inverse...

I have a question regarding the interactions of electromagnetic fields. Say you have two superconducting electromagnets A and B. The properties of the magnets are known such that you can tell precisely how quickly it takes each one to produce it's full strength magnetic field and how long it...

Homework Statement Problem: 4.93[/B] The pulley is assumed massless and frictionless. The mass of the object attached to the pulley is given in terms of m, the force applied to the pulley is F (refer to diagram), and frictional force is f. Question: Find the acceleration of the mass m in...

I am wondering if anyone knows of a good resource to see Newtons first law in action. For example, a block being pulled by increasing force until it moves?

Consider two point charges +q,+q. Separated by distance d. now there exist a point P on the line joining these two charges where electric field cancels out at distance d/2 from the charge. If we make a Gaussian surface at this point and work out the surface integral it won't be zero. since two...

why electric field intensity at a point of a non conducting sheet is independent of r?

in a 4D plane or on a four-dimensional surface can gauss law be used?

Homework Statement Using Kirchhoff’s rules, (a) find the current in each resistor shown in Figure P28.31 and (b) find the potential difference between points c and f.[/B]Homework Equations [/B] Σ ΔV = 0 (KVL) The Attempt at a Solution [/B] I have been trying to set up a system of equations...

<Moderator's note: Moved from a technical forum and thus no template.> Greetings! I've been working on basic algebra of sets. Refer to Exercise 2.4. Use the identities A = A ∩ S and S = B ∪ B and a distributive law to prove that If B ⊂ A then A = B ∪ (A ∩ B). Exercise 2.4 asked to draw Venn's...

I was thinking about the color of the sun. I would like to talk about an ideal case, no atmosphere etc. I looking for the peak in Planck's law in wavelengths (wl), i.e., the most radiated wl (or from Wien's law). But if I'm thinking about how we see that photons hitting our eyes and what wl is...

Homework Statement 1) for a given reaction to consume one reactant completely, must the equivalents of both reactants be same? for example, I know in the reaction of HCl + NaOH - the equivalents of HCl=equivalents of NaOH for a titration, is it the same for Na2CO3 + HCl? 2) the following is an...

i have heard how our broadcasts will be seen by aliens far away or whatever. but i realize those signals are going to "attenuate" by d^-2 anyway... how come in astronomy we can see light sources millions of light years away? shouldn't those signals be far too weak to detect after such a long...

Homework Statement A long, thin, straight wire of length 1.3 m has a positive charge 4.1 × 10-8 C distributed uniformly along it. The electric field created by this wire at a radial distance 3.2 cm has a magnitude of ε= 8.85E-12 Homework Equations I think I need to use E= q/(4πr^2ε) but I...

We apply Gauss's law to find electric field at a point due to chaged plane or plate. But what's wrong when applying to circular disk which can also be considered as a plane?

The Stefan-Boltzmann Law Question: Is this law proven to be true? If so, then what about sunspots? The surface of the sun is roughly double the temperature of an umbra which means it should be 16 times brighter according to this law. It isn't. The luminosity of the photosphere is 10,000...

Hello PF, in Carroll’s “Spacetime and Geometry”, he works out the transformation law for connection coefficients in his introduction to covariant derivatives, and I’m wondering if there is a typo in the final equation. He starts with$$\nabla_{\mu} V^{\nu} = \partial_{\mu} V^{\nu} +...

It seems to me that if one had a functional Alcubierre drive and used it there would be some subluminal frame of reference in which time was going backwards for the spaceship which probably for it and for macroscopic objects in it which constitute a reasonably closed system would be a violation...

Coulomb's law states that the force between particles depends on their charge. But protons and electrons have equal but opposite charges. Shouldn't the formula simply have constants with the only changes required being the signs?

I have an issue with Gauss's Law when it is considered one equation of Maxwell's complete system of equations. I don't have an issue with it when it is a standalone equation, but when it is one of several equations put together to form a complete system of equations, there is an issue. How is...

Hi, I want to calculate the amount of liquid nitrogen (at boiling temp.) needed to build a pressure of 10.1 bar in a vessel of volume 66 m3. The liquid will be poured slowly into the vessel, boil off and fill the volume with gas at the specified pressure. I make the assumption that the process...

Say you have a hollow cylinder, whose one side is open. Now, you pace a positive charge ##Q## at the centre of this open end (such that it is just inside the cylinder). How much should be the flux coming out from the closed end? I just thought of this problem. In order to use Gauss' Law, we...

I am trying to prove the generalized associative law with induction, but am being tripped up by one aspect. I am reading a solution and it says for the induction step argue that any bracketing of the product ##a_1 \cdot a_2 \cdot \cdots a_n## must break into two subproducts ##(a_1 \cdot \cdots...

Hi, so I came across this video: which shows an interesting way to solve the Basel problem using lighthouses. Imagine a lighthouse that has absolute brightness 1. The apparent brightness then follows an inverse-square law. Now imagine an infinite number line with positive integers only (and...

The research question of this experiment stated "What is the effect of changing the air pressure (kPa) inside a soccer ball on the distance (m) that the ball will travel (when it first hits the ground) as measured by using the AG500 digital air pressure gauge (to 0.01 kPa) and a field measuring...

Does anyone know a rigorous proof for Dalton's law ? I think I saw it once, but I can not find it again anywhere. Thanks Ric

Homework Statement Homework Equations ΔEsystem + ΔEsurroundings =0 The Attempt at a Solution I have solved 11a and got 5m/s. I can do 11b just by just jumping to Ek = Fs (from the work kinetic energy theorem), but I would like to do it formally from first principles using the Law of...

Homework Statement Find the admissible current density Jadm for a wire that has no insulation and also for a wire that has two layers of insulation and compare it to Jadm for the case when the wire has only one layer of insulation.2. The attempt at a solution and equations In the image I've...

Homework Statement I have the following RLC circuit with an sinusoidal voltage generator and I want to verify the Kirchoff's first law with an oscilloscope. To measure the peak voltage in each of the components I just permute the positions between the component and the resistor. The question...

Homework Statement 12kg of a fluid per minute goes through a reversible steady flow process. The properties of fluid at the inlet are p1 = 1.4bar, ρ1 = 25kg/m3, C1= 120m/s and u1= 920kJ/kg and at the exit are p2= 5.6bar, ρ 2= 5 kg/m3, C2= 180m/s and u2 Homework Equations u1 + P1V1 + (C1)2/2 +...

I know that n-body problem can be complicated, but that's for the dynamics. What about a static case: e.g. if I have the distances of several bodies A, B and C etc. and their distance to a reference mass m, can I just use the vector addition of the Newton's gravitational force to add up all of...

Ok, so just a quick question, first law of thermodynamics basically states that matter cannot be created nor destroyed aka it can only change states and turn into energy or vice versa, the second law states that, IIRC, for perfect isolated systems entropy remains constant but for our universe...

Morning, I've come across this statement in Berkeley Physics Course, Vol.1 - Cp. 5 (pg.149): "For sufficiently small displacements such a force may be produced by a stretched or compressed spring. For large elastic displacements we must add terms in higher powers of x to Eq. (,5.19): Fx = -...

Homework Statement Below is a diagram of an infinitely long non-conducting rod of radius, R, with a uniform continuous charge distribution. The uniform linear charge density of this line is lamba1. The rod is at the center of an infinitely long, conducting pipe. The linear charge density of...

Homework Statement You have a circular coil, and two metal plates a and b. The north pole of a bar magnet is moved away from the coil at a constant velocity(assume the bar magnet and the coil lies along the x axis). On which plate will the excess positive charge appear? Homework EquationsThe...

I know that dS=dQ/T for reversible process, is dU=TdS-PdV for reversible process only?

Homework Statement For a black body all absorbed radiation is emitted. Kirchoff´s law states that at the same temperature T1 the emissivity and absorptivity of a surface are equal, which holds for nonblack bodies as well. So, what really differs a black body and a non-black body in this case?

If alien were to establish a colony on earth, do they need human permission? ----------------------------------------- let's say they show up on sky where not belong to any country and create artificial island on international water to set up their own colony. even assume that they were...

Homework Statement Homework EquationsThe Attempt at a Solution I think if the law of gravitation changes then the law of areas should still hold .Law of areas is nothing but law of conservation of angular momentum . Since the changed law of gravitation is still central the law of areas...

Homework Statement The Attempt at a Solution Hi All, I have two issues with this question. First of all when I put the given values into the Bragg condition for diffraction I get two different wavelengths when the question implies there is only one. Secondly, I don't know how I can...

Homework Statement I am working on the derivation of Kepler's Second Law based on torque and angular momentum. I understand that the vector "L" is equal to the mass (m) times the cross product of the vector "r" and the vector "v." The source I am following then states that L = mrvtheta. I do...

Hello, I was solving a problem regarding pressure at different elevations. The question regarded water flowing through a pipe which travels up 5 meters. I used Pascal's Law (p = p(initial) + rho*g*h : rho is density of fluid, g is gravity and h is the height) and came up with an answer...

Hello, I am completing a research project for differential equations class. I am to derive Kepler's three laws and then compare the results of the derivation with real-world data. For Kepler's second law (a planet sweeps out an equal area in an equal time), I was hoping to find orbital data for...

Can you provide me any source from where I can learn about the overall second law efficiency calculation of a simple Rankine cycle?

Homework Statement Compare the compressor work input required to compress water isentropically from 100kpa to 1MPa, assuming that the water exists as (a) saturated liquid and (b) saturated vapor at the inlet state Homework Equations Win = v(P2-P1) Win = (h2- h1) The Attempt at a Solution...

Homework Statement A positron is moving in a circular orbit of radius r = 2cm within a uniform magnetic field B0 = 50##\mu##T. The magnetic field varies over time according to the expression: B = 700t + Bo and, therefore, each orbit can be considered almost circular. (a) Calculate the...