What is Law: Definition and 1000 Discussions

Law is a system of rules created and enforced through social or governmental institutions to regulate behavior, with its precise definition a matter of longstanding debate. It has been variously described as a science and the art of justice. State-enforced laws can be made by a group legislature or by a single legislator, resulting in statutes; by the executive through decrees and regulations; or established by judges through precedent, usually in common law jurisdictions. Private individuals may create legally binding contracts, including arbitration agreements that adopt alternative ways of resolving disputes to standard court litigation. The creation of laws themselves may be influenced by a constitution, written or tacit, and the rights encoded therein. The law shapes politics, economics, history and society in various ways and serves as a mediator of relations between people.
Legal systems vary between countries, with their differences analysed in comparative law. In civil law jurisdictions, a legislature or other central body codifies and consolidates the law. In common law systems, judges make binding case law through precedent, although on occasion this may be overturned by a higher court or the legislature. Historically, religious law influenced secular matters, and is still used in some religious communities. Sharia law based on Islamic principles is used as the primary legal system in several countries, including Iran and Saudi Arabia.Law's scope can be divided into two domains. Public law concerns government and society, including constitutional law, administrative law, and criminal law. Private law deals with legal disputes between individuals and/or organisations in areas such as contracts, property, torts/delicts and commercial law. This distinction is stronger in civil law countries, particularly those with a separate system of administrative courts; by contrast, the public-private law divide is less pronounced in common law jurisdictions.Law provides a source of scholarly inquiry into legal history, philosophy, economic analysis and sociology. Law also raises important and complex issues concerning equality, fairness, and justice.

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  1. billyt_

    Experimental investigation of Faraday's Law of Induction

    Looking at how the induced EMF is proportional to the rate of change of magnetic flux, intuitively it seems that if I increase the velocity of the magnet through the solenoid, i.e. drop it from a higher height, the EMF should increase as well. However, I am unsure if this is true and can't seem...
  2. guyvsdcsniper

    I Relating Entropy and the 2nd law

    So I am midway through my Thermodynamics course in college and still feel a bit unsure about the 2nd law and entropy. I've learned that the 2nd law was states 3 different ways, and by contrapositive proofs we can determine they are all equivalent. What we end up getting for the 2nd law is...
  3. W

    Ideal gas law- Find the pressure

    Question: Answer: In the third last line of working, I do not understand why the pressure variable is changing? Shouldn't pressure remain constant and only the Volume change?
  4. rudransh verma

    B Same case of Newton’s third law

    Previously I have posted two threads on Thread 'Monkey climbing up the rope' https://www.physicsforums.com/threads/monkey-climbing-up-the-rope.1012065/ and Thread 'Car's maximum acceleration on a road is proportional to what?'...
  5. guyvsdcsniper

    What is the Proof for Newton's Law of Cooling Formula Using Quadratic Equation?

    I have went about this problem many different ways but cannot seem to come up with the answer. I am essentially trying to prove the formula provided in the ss of the problem.Could someone help me and tell me if I am approaching this wrong?
  6. A

    Application Of Kirchoff Law (Desert)

    Homework Statement:: Sand is rough and black so it is a good absorber and radiator of heat depending on temperature. During the day, sand's radiation of the sun's energy superheats the air and causes temperatures to soar. But, at night most of the heat in the sand quickly radiates into the air...
  7. dliu1004

    Question on a Gauss's Law problem

    Summary:: I understand the basics of Gauss's Law and how to solve some of the simpler problems, but I cannot seem to solve these two questions. For question 007, one of my friends told me I had to ignore the outer shell? I did that: I integrated rho dV: (6.02*r*pi*r^2*h) from r=0 to r=.0462...
  8. rudransh verma

    B Newton’s second law as one complete law

    https://www.feynmanlectures.caltech.edu/I_08.html Page 9-3. It says “In these terms, we see that Newton’s second law, in saying that the force is in same direction as the acceleration,is really three laws, in the sense that the components of force in the x, y,z directions is equal to the mass...
  9. aladinlamp

    A Betz Law & Submerged Turbines: Is it Applicable?

    Hi, is Betz law fully applicable for hydro, hydrokinetic submerged turbines, since air is compressible but water is not ?
  10. S

    Inverse square law of gravitation and force between two spheres

    I recently encountered this problem on a test where the solution for the above problem was given as follows: $$F= \frac{Gm_1m_2} {r^2} $$ (1) but $$ m=\frac{4}{3}\pi R^3 $$ substituting in equation (1) $$F= \frac{{G(\frac{4}{3}\pi R^3\rho})^2 }{2R^2} $$ where r=radii of the two spheres m=mass...
  11. D

    B Infrared Detectors & The 2nd Law of Thermodynamics

    This started as an astrophotography question and morphed into a thermodynamics question & it was suggested to start a new thread in Thermodynamics. Essentially the question is how do I reconcile the behavior of particular infrared photodetectors with the 2nd Law of Thermodynamics? For example...
  12. NoahCygnus

    How to use Kirchhoff's voltage law on this circuit?

    In this circuit, I have to find the potential at point O. I tried using Kirchhoff's voltage law for the three open loops AOC, AOB and BOC to arrive at potential at O. According to my calculations the potential at O should be 0, but that is not the case according to the source. So I must be using...
  13. S

    Kepler's Third Law vs Conservation of angular momentum

    The classic way to go about this problem would be to use Kepler's laws and thus find the new time period of earth. However I encountered this question in a test on rotational motion which deals with conservation of angular momentum. The equation used here would be I1ω1= I2ω2 Replacing I with MR2...
  14. Arsene11

    Newton's law question involving force and acceleration

    I have no idea what to do but the answer is V=V0+ bt +(ct^3)/3
  15. Leo Liu

    I Gauss' law and an object with nonuniform charge distribution

    Gauss' law: $$\iint_{\partial A}\vec E\cdot d\vec A=\frac{Q}{\epsilon_0}$$ Suppose we have a unevenly charged non-conducting spherical shell, in which a Gaussian surface is placed. In this case, is the electrical field on A 0, given that there is no charge inside A? I came up with this example...
  16. Eobardrush

    Help in solving an electricity circuit problem involving Kirchoff's law

    My initial solving method was taking 1.75A and adding the resistors at the 1st loop(4 and 8 ohms) to get the answer V=IR V=1.75(4+8) V=21V But the answer sheet uses 0.75A instead of 1.75A to find EMF of E1. So according to the answer sheet its V=0.75(4+8) V=9V 0.75A is the answer for the i)...
  17. D

    B HFC-134a Refrigerant & 2nd Law of Thermodynamics

    I am trying to reconcile HFC-134a refrigerant with the 2nd Law of Thermodynamics. I shouldn't be able to extract useful work from a single temperature reservoir. Suppose I use a refrigeration / heat pump cycle with HFC-134a as shown below. -Compressor adds 29 kJ/kg increasing refrigerant...
  18. bluesteels

    How Does Lenz's Law Explain Magnetic Field Directions?

    This the images of the figure. I am confused on why is the magnetic field for the top wired is out and the bottom is in. Is that the general rule?? Moreover what if the wired is point to the left instead of right is the magnetic field still out of the page.
  19. B

    I Proving Torricelli's Law Using Bernoulli's Principle

    There is a standard proof of this kind in which two points are taken - one at the top of the water and one just outside the spout or opening. I guess my question kind of assumes that you've seen something like this. A key step of the proof is to say that the difference of pressures, perhaps...
  20. bluesteels

    Quick question about which radius to use on Gauss' law problem

    confused on part A/B when I look up they did E= Q/2e(0.8)^2. But why not use the 0.100mm because that is the area of the enclosed. Same with B why did they use 100m and not 0.8m because 0.8 is smaller so it enclosed the charge
  21. bluesteels

    Electric field / Gauss' Law --

    Electric Flux = E*A = 5*6(0.05)^2. when i look up at other sources they use Electric flux = q/ (8.854*10^-12 [this is e]) equation but I am confused on why the E*A equation don't work. The answer is 0.02Nm^2/C
  22. R

    Newton's second law (My turtle named Newton being accelerated)

    https://www.khanacademy.org/science/physics/forces-Newtons-laws/Newtons-laws-of-motion/a/what-is-Newtons-second-law How do I find the horizontal right components force? It states it is 22 N but there is no reason that the left horizontal component is the same as the right. I thought the...
  23. jaketodd

    B According to Newton's 3rd Law....

    ...every body exerts an equal and opposite force, than what's put to it. So, when I hit a bug in my car at 50 mph, why doesn't it crack my windshield? This is probably a very basic question, with a very basic answer. I took high school physics, and also one physics class at college, but I...
  24. S

    I Antimatter-matter asymmetry, Law of charge

    I'm new to Astrophysics and I'm just now learning about Antimatter-Matter asymmetry. I understand some of the theories involving how this imbalance couldve occurred, but I'm confused on why the net charge of the universe stayed at zero. It seems to me like if the antimatter particle changed to a...
  25. dbabic

    A Spontaneous and stimulated emission in Planck's radiation law

    Hello, Einstein introduced stimulated emission (along with spontaneous emission and absorption) to derive Planck's radiation law using his A and B coefficients in his 1917 paper. My question is, is it possible to separate the Planck radiation spectrum into a fraction that is spontaneous...
  26. E

    Simple conceptual question about Ohm's law

    Hİ :) as you know potential difference in point A to B is equal to the battery's voltage and point A's current is equal to point B's current.So current is I=Q/t , there should be equal charge passing through at same time so how could there be potential difference when there is equal amount of...
  27. Hamiltonian

    Force between charged Ring and Rod, disproved Newtons 3rd law?

    This is the initial setup of the problem: The electric field due to the ring is: $$E = \int\frac{k(dq)}{(\sqrt{R^2 + x^2})^2}\frac{x}{\sqrt{R^2 + x^2}} = \frac{kqx}{(R^2 + x^2)^{3/2}}$$ the force on the rod due to this Electric field produced by the ring is: Consider a differential element...
  28. Z

    On which objects can we apply Gauss' Law to find the electric field?

    What am I missing? I also don't get the title of the section: "Charge distributions with enough symmetry for Gauss's Law". I thought Gauss's Law was valid for any closed surface enclosing a charge. I don't understand what "enough symmetry" means in the title above. I get that with symmetry...
  29. tiago000000

    Exploring the Law of Conservation of Energy with a 5kg Weight and 10L Bucket

    Hi everyone! I regularly use the forum to learn but never registered to post anything, as I have nothing to teach really… But today I have a question regarding the law of conservation of energy that I can’t find the answer to, and maybe someone will help me understand: (I’ve attached a drawing)...
  30. Franklie001

    Newton's second law -- Crate sliding in the back of an accelerating truck

    Hi everyone is able to help solve this question for my assignment in university? I've draw a free body diagram for each component of the question but now i am stuck. [Mentor Note -- Poster has been reminded to show their work when starting a new schoolwork thread]
  31. L

    At what frequency can Planck's law be used to determine the temperature?

    Hi, I am not quite sure if I have calculated the homework correctly :-) I proceeded in such a way that I first calculated from which frequency the two terms are equal, and thus the equation results in zero. Then I figured a relative accuracy of 10% equals a relative error of 90%. So I...
  32. E

    B Question about magnetizing and the First law of Thermodynamics

    I've been learning a lot about life from Internet searches and I do hope this isn't too basic of a question for you gurus. If I had two pieces of iron next to each other with a pea in-between and two pieces of cobalt with a pea in-between. Then I magnetized the four pieces of metal by brushing...
  33. M

    Engineering Kirchoff's Law Problem about this Induction Generator circuit

    Hi, Please find attached below the Induction Generator circuit. I have the following parameters: Parameter Value Rs = Rr (Resistance on stator and rotor) 0.2 Ω Ls = Lr (inductance on stator and rotor) 5 mH = 0.005 H p (number of pairs of poles) 2 f (frequency) 60 Hz Vsl (stator line...
  34. guyvsdcsniper

    Different forms of Biot-Savart Law

    My book never references the Biot-Savart law with in terms of 1/r^3, only 1/r^2. How is it that it can be expressed as 1/r^3 as well
  35. E

    Gauss' law and flux concept issues

    Hi guys i have some concept issues about flux. My book says flux is proportional to the number of lines passing through that area. so my question is: first i am thinking that a 2D circle which has a 2r diameter and it is enclosing a 2q charge so its flux should be 2q/Epsilon.then i am thinking a...
  36. K

    A Hooke's law, Bertrand's theorem and closed orbits

    Bertrand's Theorem says : the only forces whose bounded orbits imply closed orbits are the Hooke's law and the attractive inverse square force. I'm looking at the hookes law ##f=-k r## and try to see explicitly that the orbit is indeed closed. I use the orbit equation ##\frac{d^{2} u}{d...
  37. Y

    B Why is Julius Sumner Miller saying Torricelli's law is not correct?

    Hello, I'm just starting my research on a project I would like to build. But the design on the project has been delayed until I can get a concrete answer to this problem. I grew up loving the "The Professor" segments on a kids show from the 70's called "The Hilarious House of Frightenstein"...
  38. mohammed

    Solving Electric Field Vector Problems Using Gauss's Law

    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...
  39. curiousPep

    Confused about which forces are external when Newton's Second Law is used

    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...
  40. kekkeroo

    Why a transformer cannot use DC (Ampere's law)?

    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?
  41. A

    Ohm's law, current density, free & bound charge

    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...
  42. questionmonkey123

    Constant pressure process (piston) on gas violates Newtons 2nd law?

    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...
  43. S

    Newton's law problem: Helicopter lifting a box with a rope

    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...
  44. S

    A Any model or theory in physics akin to "Law without law"?

    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...
  45. E

    I finding resultants using sine/cosine law

    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?
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