Law Definition and 999 Threads

  1. FEAnalyst

    Newton's law of cooling - formula for constant k

    Hi, recently I got interested with practical applications of Newton's law of cooling. Its main disadvantage is that one has to measure temperature at some point of time (other than ##t=0##) to obtain solution for any other ##t##. However I've found an online calculator...
  2. DaveC426913

    Canadian Law: Injunctions - complete newbie

    Asking for a friend. Hypothetically. Say my friend, hypothetically, had an injunction that forbade him from entering his own apartment or having any "direct or indirect contact" with his partner. Say there's a court date pending in a few weeks. Let's assume it's an interim injunction. And...
  3. R

    Question about the first law of thermodynamics

    In thermodynamics, the internal energy (U) is the function of the volume (V) and temperature (T), U = U (T). Therefore, according to the mathematics, dU = π dV + Cv dT, where π is internal pressure and Cv is the constant volume heat capacity. Meanwhile, according to the 1st law, dU = δ w + δq...
  4. Riemann9471

    Rewriting the Ampere's law in term of free currents only

    This is not really the assignment of my homework ( my assignment require me to find the magnetic field inside a small air gap on a toroide magnet wrapped with N turns of a wire that carry a current I ) . I'm at some point in the solution where I kind of need to use the rewritten Ampere's law to...
  5. yecko

    Why is the change in entropy of a heat pump in one cycle equal to zero?

    as it is not ideal, total change of entropy > 0 entropy loss of hot reservoir > entropy gain of cold reservoir why would the change in entropy of the heat pump in one cycle equals to zero? thank you
  6. S

    I Proving Gauss' Law using a Cubical Surface

    Hi, I'm trying to prove Gauss's Law by using a cubical surface with a point charge located at its center, and I'm running up against some difficult integration. I've worked through the first integral of the surface integral, but I can't seem to figure out a proper integration technique. Here is...
  7. Tryingtolearn123

    Conceptual understanding/question of guass and Coulomb’s law

    Homework Statement: This is more of a conceptual question for those already experienced with Gauss law and Coulomb’s law. As far as being able to look at a problem and knowing exactly how to solve it from the very beginning. Often looking at solutions and doing the math of a single problem can...
  8. D

    Where Does the N in Faraday's Law of Induction Go?

    Hello Lets take an example: imagine a horizontal magnetic field, then a wire of length L. I push the wire with a force F through the field perpendicularly with respect to the magn. field for a distance of dS. EMF = work/charge --> F*dS/I*dt, where F = flux density*current*lenght of conductor...
  9. D

    Ampere's law in differential form

    According to this image, in the attached files there is the demonstration of the ampere's law in differential form. Bur i have some difficulties in understanding some passages. Probably I'm not understanding how to consider those two magnetic vectors oriented and why have different name. in...
  10. jisbon

    Calculate the time for a spacecraft to arrive at Mars (No Kepler's law)

    So I've seen many similar questions like this on the internet, but they all involve using Kepler's law, which is not in my syllabus in my case. However, they do give me the mass of the Sun. which I assume involves gravitational force/field/circular motion? The question also gave me a hint that I...
  11. X

    I Challenges to the Redshift Method and Hubble's Law

    Since Hubble's Law has been around a long time, so, after almost 100 years, to challenge its validity looks like dumb and stupid. So let me be that dumb guy, or maybe the bad boy that spoils the whole thing. Here let me start with the Redshift in general. There are three Redshifts proposed till...
  12. D

    Confused about Newton's 3rd law

    Hi. I am confused about the use of Newton's 3rd law in the following situation. If someone steps horizontally out of a skyscraper with zero vertical velocity. Then obviously they fall downwards. But if i apply Newton's 3rd law ; persons weight act downwards on the air so doesn't the air apply an...
  13. Kaushik

    Stokes' Law: Why does viscous drag depend upon the radius of the spherical body?

    Stokes' Law gives us the value fo viscous force when a spherical body is under motion inside a fluid. ##F_{viscous} = 6\pi\eta av## (where ##a## is the radius of the spherical body and ##v## is the velocity with which it is moving) What is the reason for the Viscous drag to depend upon the...
  14. nmsurobert

    Boyle's Law and Applied pressure

    When using a Boyle's Law Apparatus, pressure applied to the plunger can be calculated by knowing the mass of the object on the plunger and the area of the plunger. P = F/A. The change of pressure inside the cylinder can be calculated using Boyles Law, P1V1 = P2V2 Should the value for the...
  15. Jelsborg

    Why Does Gauss' Law Yield Different Results for Spherical Charge Distributions?

    So the first problem stated is to show that for a charge distribution between two spherical shells of radii r1<r2, the total charge inside is described by: This is rather trivial using Gauss' law in integral form, so I regard this as completed. I have used the gradient to find the electrical...
  16. K

    Electric field using Gauss's Law, but in open cylinder given only r?

    I have no idea how to approach the problem using Gauss's Law. I found the electric field using superposition, and it was incorrect. I am assuming you treat the wire as a continuous electric field, and then also treat the pipe as a continuous electric field. I solved for this using...
  17. warhammer

    A Conceptual doubt in a problem on Wien's Law

    Given λ=700nm, we use the equation mentioned above and find the Temperature to be 4140K. However, my doubt is that the wavelength specified to be used above is a maximum and I'm not sure if the answer is (a) or (d) considering that the latter is a range of the temperature.
  18. E

    Debate over the experimental procedure for Newton's 2nd Law

    Hi, I'm currently having an ongoing debate with some teachers regarding a practical for Newton's Second Law. The prac involves a cart attached to some weights via a string on a pulley. The protocol as it stands has students add increasing mass to the end of the string (not changing the mass of...
  19. Luxucs

    Faraday's Law & Motional EMF Confusion

    Hi there! I have what I hope is a relatively straightforward question regarding Faraday's law and motional emf, but its been causing me to scratch my head for quite a while. Consider the diagram attached to this post (source is linked at the bottom). Assume that all of the wires and the rod are...
  20. Sonim

    Can a Calorimeter Measure Fast Chemical Reactions?

    My book introduces Thermochemistry with the concept of heat and how a calorimeter works. After that, it explains the story behind Hess Law and says that one of the reasons it was created is because a calorimeter can't calculate fast chemical reactions, but it doesn't really say the problem with...
  21. B

    Newton's Law of Cooling - "k" constant

    Hi, I have been exploring Newtons Law of Cooling. What relationship should i expect to see from the cooling constant "k". I have plotted the "k" values for each equation that i have developed (based off of different volumes of water in the same sized beaker). So, when the "k" vs volume graph is...
  22. M

    Inverse Power Law: Solve for Power at 400m

    Hi everyone! Awesome forum! I'm doubting myself on a problem about inverse square law. I'll change the actual values from my homework problem as I want to check that I have the right idea rather than the specific numeric answer. If I am using an inverse 2.5 power law and know the power at 100m...
  23. christang_1023

    I What is the addition law for probability with multiple elements?

    The additional law with two elements can be expressed $$P(A\cup B)=P(A)+P(B)-P(A\cap B)$$, while the law with three elements can be $$P(A\cup B\cup C)=P(A)+P(B)+P(C)-P(A\cap B)-P(B\cap C)-P(A\cap C)+P(A\cap B\cap C)$$ Now I wonder if there is the more general form of addition law, which applies...
  24. bryanso

    A Question about Albert Shadowitz's Explanation of Ampere's Law

    In Shadowitz's book The Electromagetic Field, Section 3-4, p. 129 to 134, there is a very interesting derivation of Ampere's Law. It is a general derivation with a circular source circuit S, and a circular test circuit T. The pages can be seen here, at least from where I post (USA)...
  25. B

    Faraday's Law and the distance from another wire

    Hello, I have a conceptual question regarding Faraday's Law: emf = d/dt(Φ), where |Φ|=|B*A|. My question is does Faraday's Law take into account the distance between the solenoid producing the non-coulombic electrical field (Enc) and a wire circling the solenoid, which now have an emf due to the...
  26. M

    How to characterize a power law field?

    Hello, as part of the study of fields with central forces, I came across with fields called power law, defined by F = - K/r ^ n u (u is radial vector passing through the origin O) I would like to dismiss case n = 2, which refers to the Newtonian fields whose study was exhaustively conducted in...
  27. A

    AIK, this is the best I can do for you.

    Carnot's postulate: one cannot build an engine whose sole effect is to transfer heat from a cold body to a hot body. How granted this postulate can I prove that no engine beats Carnot's engine? From this postulate, I can conclude that work must be done from the surroundings and that Carnot's...
  28. Paul Lasdivan

    Engineering Can I solve this using Kirchoff's Law?

    We were given a circuit with 7 resistors and 3 voltage sources For emf sources, ##E_1=120V##, ##E_2=60V##, and ##E_3=30V## while for resistors in ohms,##R_1=10##, ##R_2=5##, ##R_3=20##, ##R_4=8##, ##R_5=12##, ##R_6=6##, ##R_7=8##. Nodes are indicated in small letters (a-j). Loops ##abefa##...
  29. Hawkingo

    What is the effect of the dielectric material on Gauss' law?

    [PAGE 1] [PAGE 2] [PAGE 3] so in the 2nd page,when the dielectric material is introduced the gauss's law becomes $$\oint _ { S } \vec { E } \cdot \vec { d S } = \frac { ( q - q _ { i } ) } { \epsilon _ { 0 } }$$.But my question is why the ##{ \epsilon _ { 0 } }## is in the equation.Shouldn't...
  30. S

    I Apply Conservation Law to Euler-Lagrange Equation

    In my most recent thread, I discussed the conservation law involving the 4-velocity vector: gab(dxa/dτ)(dxb/dτ) = -c2 Now, I've read that you can apply this law to the Euler-Lagrange equation in order to get some equations that are apparently equivalent to the geodesic equations. Now here is...
  31. rofldude188

    Faraday's Law - Balloon Problem

    a) Calculate the proposed induced emf along the equator of the balloon. (horizontal equator), at the moment indicated above. $$V(t) = V + Ft \implies \frac{4 \pi r^3(t)}{3} = V + Ft \implies r(t) = \sqrt[3]{\frac{3V+3Ft}{4 \pi}}$$ $$\phi = B \pi r^2(t) = B\pi (\frac{3V+3Ft}{4 \pi})^{2/3}$$...
  32. jdou86

    Can someone please explain to me how the Biot Savart law is derived?

    Problem Statement: Precised to its constant . Thank you! Relevant Equations: Below En
  33. S

    I Learn About Conservation Law & Geodesic Equation

    In my quest to learn how to solve the geodesic equation, I came across this law which apparently holds true for all metrics (according to what I read): gab(dxa/dτ)(dxb/dτ) = -1 Well, I tested this formula out with Minkowski space (- + + + signature): If I understand correctly, then in...
  34. N

    Find the Electric Field E using Gauss' Law

    I tried to work out both a) and b), but I am not sure if I am correct. I drew a picture with a sphere around q first with radius r and then with radius 3r. For a) ##E.A=\frac {q}{ε_°}## (when using Gauss' Law) Since ##A=4πr^2##, I substituted this in the equation and solved for E giving me...
  35. M

    What is the Correct Approach for Solving Faraday's Law Problem?

    This seems like just another Faraday's Law problem, but I'm getting the wrong answer according to the book. I think I'm only calculating the answer for the interval ωt = 0 and ωt = pi/2, when the |B→| is increasing. Basically you just calculate the magnetic flux through the area of the loop...
  36. N

    Ideal Gas Law in Two Dimensions

    I am creating a two-dimensional model of an ideal gas, and I was wondering how I should determine initial velocity. Ideally, I would like for the simulation to reach a point where the velocity distribution resembles that of the maxwell-boltzmann curve — will this be achieved if I, say, assign...
  37. A

    Does the First Law of Thermodynamics Allow for Heat Generation During Stirring?

    Consider a system composed of a gas+stirrer at state 1, Work is done on the system by a rotating shaft, the stirrer activates high speed generating a significant amount of heat. The system is undergoing a process because the set of measurable properties to define its state are changing, If I...
  38. adamaero

    By using Gauss' law, can the electric field be p/(pi*ε*r^2)

    Which is better to use? The equation for the area or the circumference of a circle? Schaum's Electromagnetics (4 ed) by Edminister vs http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecyl.html
  39. A

    Newton's Second Law — Net Force problem

  40. A

    Newton’s Second Law applied: F=ma

    My attempt at solving this written out with random inputs Block A- F(100)=M(10)A(10) Block B- F(200)= M(15) A A=200/15 = 13.33 This was not in line with options.. which were 4x block A (1/4) block A Equal to block A (1/2) block A 2x block A Much appreciated some help as I am a beginner
  41. hisacro

    Ampere's circuital law -- Monopole thought experiment

  42. F

    B Why is the distributive law correct in algebra, like in arithmetic?

    When they give reason for multiplication the negative numbers leading to positive number, they base on distribute law.But why the distribute law in algebra is correct like in arithmetic?(e.g why -5(8-6)=-5.8+-5.-6?).In abstract algebra they use distribute law as axiom.But in elementary algebra...
  43. akashpandey

    I Triangle law of vector addition and the Pythagoras theorem

    i know its pretty basic but please give some insight for triangle law of vector addition and pythgoras theorem. becuase ofcourse if you use traingle law to find resultant it will be different from what is pythagoras theorem
  44. QuasarBoy543298

    Question about the 0th law of thermodynamics

    assume I have 3 systems a,b and c. the equilibrium between a and c can be described by the equality PcVc = f(A1,..., An) and the same for b and c - PcVc = g(B1,...,Bk). why does the equality g(B1,..., Bk) = f(A1,..., An) describes an equilibrium between A and B? the 0th law states that if A and...
  45. T

    Appropriate Language when Discussing Faraday's Law

    Quick question, when discussing induce emf, would you state: "An emf is induced in the coil..." or "An emf is induced across the coil..." The reason I ask is that grammatically, it sounds proper to state "An electromotive force is induced in..." (something). However, an emf is a potential...
  46. K

    Why can't we use Ampere's Law?

    We are asked to find the magnetic field at point P, all of the quantities in the figure are known values and the current density is uniform. One way to solve this problem is by modeling the sheet as a collection of infinitely long wires, with each wire contributing an amount of magnetic field dB...
  47. bob012345

    How Does the Vector Potential Influence Faraday's Law of Induction?

    Suppose there is an almost infinitly long but narrow solenoid with an AC current surrounded by a much larger loop such that there is no magnetic field except in the solenoid. I had always thought it didn't matter what part of the outer loop the flux changed in, there would be an induced electric...
  48. S

    Pendulum's Tension using Force reasoning and Newtons 3rd Law.

    Hi, I have a conceptual question. I was doing some problems on pendulums and found something that confused me. I attached a drawing. I used to always solve these problems by using some trigonometry and trying to find the Tension. i.e. ## m*g = F (of the Tension) * cos(theta) ## so ## \frac...
  49. ArcHorizon

    Calculations using the Ideal Gas Law

    2.1 * 10^-4m/3 Temperature 310K Pressure: 5.3 * 105 Pa So the Ideal gas formula is PV = nRT 2.1*10^-4m^3 Times 5.3*105Pa = n * Gas Constant * Temperature 2.1*10^-4m^3 (*) 5.3*105Pa = # of moles * I'm not sure what I was doing, but the whole equation stuff got hard and I stopped. I left...
  50. archaic

    B Trying to understand the basics of Hooke's law

    Hello, I need some help on understanding what this book is trying to convey. How does "any part of the spring acts on another part"? Doesn't (2.25) just give us the "operator force" and, since the spring is at equilibrium, the elastic force? What exactly is strain? And I am failing to see the...
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