Laws Definition and 1000 Threads

  1. T

    I Do laws of physics apply below the event horizon?

    Do laws of physics apply below the event horizon? It appears as if black holes had such gravity as to have an escapr velocity higher than c, which means that things are pulled inwards at higher speeds than the speed of light. Or am I overlooking something?
  2. FallenApple

    I The Trade-Off Between Simplicity and Intuition in Scientific Theories

    So it seems there is predilection in physics to go after simple and elegant models of physical reality. That is, parsimonious models are preferred. Sometimes this means that there is a trade off between mathematical elegance and intuition. For example, if theory A and theory B both perfectly...
  3. FallenApple

    I Would quantum laws work in other hypothetical universes?

    Not saying that there is another universe. But if there were, would the laws be the same? I've heard Leonard Susskind explain that extraneous solutions of string theory could represent the environment in regions very far "away". So is it just small things like the physical constants being...
  4. E

    The Normal Force on a Carousel: How Does it Affect Weighing Scales?

    Homework Statement [/B] A boy with a mass of m1 is sitting in a carousel. The spinning frequency is 0.3355. The boy is also sitting on a weighing scale, will they show a number higher than m1g,lower or the same? (The mass of the weighing scale is 0). Homework Equations mω2r=F ma=F ω2=4π2f2...
  5. G

    Combining Newton's Laws and Kinematic

    Homework Statement Max (65 kg) pushes Toni (50 kg) with a force of 360 N. The force of friction is 0 on Toni and 80 on Max. (a) Find each girls acceleration (b) If Max pushes Toni for 0.1 s, how far will Toni travel in 0.5 s? Homework Equations Fnet=ma v2=v1+at d=v1(t)+1/2a(t)^2 The Attempt...
  6. J

    Hard Kirchoff's Laws problem with batteries & resistors....

    Homework Statement Homework Equations Kirchhoff;s first and second law, V=IR The Attempt at a Solution Tried the question as follows: V= 24/(2+6+4) = 24/12 = 2V (pd from top cell) then did 2=4 I3 therefore I3 = 0.5A and then 2 = 6I2 I2 = 0.33A and I1 = 0.5+0.33... =0.83A?
  7. NihalRi

    Using Kirchoff's laws to find current in complex circuit

    Homework Statement Homework Equations V=IR and kirchhoffs laws The Attempt at a Solution Number three is my attempt at finding a solution but I got stuck when I had to find an expression for loop one on the diagram. Thanks in advance for your help...
  8. P

    How to apply Newton's laws to non-rigid bodies?

    Suppose we have a body of finite size which can be translated, rotated, compressed and stretched. We have every information about the body. We have its dimensions and everything. We have its mass and density. But, since I'm here talking about a completely generalized version, so we have variable...
  9. gkamal

    DC Circuit Analysis: Kirchhoff's Laws

    1. Homework Statement A DC circuit is shown below. Note the ground (V=0) in the circuit 1- calculate the current through the 5Ω resistance. Use "+" sign for the current directed from right to left, and "-" sign if the current flows from left to right. 2- The sign of the potential at a is...
  10. Mert Kerem Yavuz

    Applying Newton's Laws, motion with constant acceleration

    Homework Statement Homework Equations F=m*a ΣF=0 The Attempt at a Solution Firstly, I tried to work on the normal force of bowling ball. But I can't get the answer. I don't get the idea that bowling ball could be kept at constant height, I didn't really understand the question guess. Can...
  11. L

    Confusion about Newton's laws, sum of forces equals zero

    I've lately began working with Newtons laws problems at school again, and I've already ran into a few problems. When making calculations and solving problems, it is often nessecary to understand when forces are equal to zero, and when they are not. Since every force has an equal and opposite...
  12. P

    I Invalidating a patent directed to physical laws

    I'm an attorney trying to invalidate a patent that I believe is directed to patent-ineligible subject matter. It's been an interesting exercise, and I'd love to hear other ideas/suggestions/etc. on how to approach it. At a high level, the patent claims certain structures with a certain...
  13. E

    Possible confusion regarding application of Kirchoff's Laws?

    Homework Statement Determine Currents ##I_{1}, I_{2}, I_{3}## Homework Equations Kirchoff's Rules: $$\sum_{i=1}^n I_{i} = 0$$ $$\sum_{i=1}^n V_{i} = 0$$The Attempt at a Solution Basically, I'm not sure if I'm applying the Loop Law correctly. For example, in Loop A, going clockwise from...
  14. Lauren0619

    Newton's Laws - Incline. Do I have the right idea?

    I am hoping that I can have someone look over my answers. I have provided what I think is necessary to be appropriate posting, including the questions and attempts at all my answers. I would just like some feedback that I am correct in my answers. Thank you! This is an overview that all the...
  15. F

    A How Do Conservation Laws Apply to a 4 Current in General Relativity?

    Consider a 4 current J^\mu and a metric g then conservation laws will require \del_\mu J^\mu = 0 my lecturer gave me a brief problem and I think I'm missing some understanding of it he writes What I'm not understanding is, where he states, if we choose B to be the time slice between etc...
  16. counlin

    Laws for goods delivery around the world?

    Hello, So, I'm posting this question here because I can't think of a better place, and also here there are people from all over the globe. The thing is, I'm doing some research on Delivery of Goods and Laws related in Brazil. But, to have some base, I want to make some comparisons with laws...
  17. Morrissey

    What are the reaction forces to the external forces on the wagon in (b)?

    Homework Statement One or more external forces are exerted on each object enclosed in a dashed box shown in the figures below. Identify the reaction to each of these forces, assuming that (b) occurs on Earth. Select all that apply. (b) the wagon exerts a force · downward on the Earth...
  18. M

    Conservation laws in rotational movement

    Homework Statement Consider a uniform rod of mass 12kg and length 1.0m. At it's end the rod is attached to a fixed, friction free pivot. Initially the rod is balanced vertically above the pivot and begins to fall (from rest) as shown in the diagram. Determine, a) the angular acceleration of...
  19. Cocoleia

    Use Kirchoff's laws to solve for tension and current

    Homework Statement http://postimg.org/image/ys43ylstp/ [/B] I need to find tension and current in each element of the circuit. I have included an image of what I have drawn so far for the circuit. http://postimg.org/image/ys43ylstp/ Homework Equations Kirchoff's laws. The Attempt at a Solution...
  20. G

    Field-free formulation of ED: Conservation laws?

    Hi. In the (mainstream) books of electrodynamics I know, the electric and magnetic fields are introduced as force fields normalized to a charged test particle of 1 C. This makes those fields appear as an unnecessary, but convenient mathematical tool. They cannot be measured in the absence of...
  21. physicsBabyMetal

    What's the relation with Gravity & Laws of Thermodynamics

    Here's a thought from other thread A reply So what's the relation between gravity and the laws of thermodynamic, or should it be conservation of energy?
  22. V

    A Geometry and integral laws of physics

    Reading the English translation of Einstein's seminal paper on GR. http://einsteinpapers.press.princeton.edu/vol6-trans/90?ajax This paragraph below on p78 doesn't make much sense to me. Could you provide a second English translation or even adding math notation. "Before Maxwell, the laws...
  23. E

    Field transformation laws - Relativity

    Homework Statement The electric and magnetic fields of a 1 Coulomb charge Q are measured by a pair of field measuring instruments. From the perspective of observers in frame O, the charge is at rest at the origin and one of the field-measuring devices is also at rest, with position (x,y,z) =...
  24. M

    I Proving the Implication of p and (p -> q) to q without Truth Tables

    Hello everyone! I want to proof that: ##p \land (p \to q) \Rightarrow q## I know this is a quite trivial problem using truth tables, however, I want to do it without it. As I'm learning this myself, is this the correct approach? ##p \land (p \to q)## ##\iff p\land (\neg p \lor q)## ##\iff (p...
  25. DumSpiroSpero

    Mechanical Energy and Newton's Laws

    Homework Statement A block of mass ## m ##, attached to a rope, is dropped at the point A. When the block reaches the point B, the tension is ## T = 2 \cdot m \cdot g ## and the rope broke at that same point. If the length of the rope is ## L = 6cm ##, evaluate the height ## h ## where the...
  26. Akshat

    Exceptions to the Laws of Physics: Newton's Third Law

    I've been noticing that there are exceptions to every scientific law. For Example, with Newton's First and Second Laws are totally invalid at the quantum level, but I'm failing to find such an example for Newton's Third Law. Is anyone able to help me?
  27. P

    B Orbital Mechanics: GR vs Newton's Laws

    9/1/2016 Orbital mechanics Wikipedia, the free encyclopedia This reference states: "General relativity is a more exact theory than Newton's laws for calculating orbits, and is sometimes necessary for greater accuracy or in highgravity situations (such as orbits close to the Sun)". Can GR...
  28. R

    Newton's laws and their implications on plain old geometry

    So, I'm reading a physics book, and it talks about Newton's three laws, of course, but then after that it says that if a force of f pushes on an object at angle Θ, then the force in the x direction is f ⋅ cos(Θ), and the force in the y direction is f ⋅ sin(Θ). Where did THAT come from? Do we...
  29. K

    Free-body diagrams and Newton's laws with a suspended chain

    Homework Statement The chain comprising three rings (each of mass ##0.25kg##) is suspended from a massless rope, and a pulling force ##\left(F=9N\right)## is exerted upwards on the rope. Picture: http://i.imgur.com/xeaiBsc.jpg?1. I need to find the values of all the unknowns. Homework...
  30. Sqrt

    What is the net force on Box H when pushing on Box G with a horizontal force?

    Homework Statement Two cardboard boxes full of books are in contact with each other on a friction less table.Box H has twice the mass of Box G. If you push on box G with a horizontal force F, then box H will experience a net force of? 2. The attempt at a solution Let book G's mass be = m...
  31. S

    I Black holes, pure classic micro-states and area laws

    Dear All Gravitinos, It seems that the current string theory and loop gravity's explanation for the micro-states of black holes are all quantum mechanical and have no classic correspondence. I, in this day's arxiv, post a pure classic interpretation for this question, titled "Black...
  32. D

    I If c changes w/ time, what happens with laws of SR?

    Howdy, Was wondering if you guys would mind critiquing, correcting, or adding any good insights to the following which was posted elsewhere by me, thanks! ________________ ... remember a ways back there was a finding that went viral about the speed of light not being constant? I forget the...
  33. Erenjaeger

    B Kepler's Laws of planetary motion

    Whose observations did Kepler use to prove that planets do in fact orbit in ellipses ?? Was it Tycho's observations? Thanks.
  34. J

    Additivity of mass: provable from Newton's laws?

    Within the context of Newton's laws, it seems implicitly understood that mass is an additive property of objects. My question is: should this be considered "just" an experimentally confirmed fact, or is is provable from Newton's laws? The following is a more precise context for this question...
  35. O

    B Hello all, lay-man's question about gas laws

    Hello all, I have perused this forum for a while now. I've never signed up because I have nothing to offer you folks. I'm not evan an amateur, I'm just interested in physics. I'm a critical care / flight medic, so my understanding of physics is really, really, really limited. Although, I'm...
  36. Evangeline101

    Newton's Laws -- Resting hockey puck hit with a force

    Homework Statement A resting hockey puck is hit with a force of 15.3 N. The frictional force slowing the puck down is 1.0 N. a) Find the net horizontal force acting on the puck while the stick is in contact with the puck. b) If the puck leaves the stick with a velocity of 45 m/s, how far will...
  37. T

    I How Does the Distributive Law Simplify Logical Expressions?

    Im just reading this one example and i am stumped at this one step. (R\to C) \land (S \to C) \\ (\neg R\lor C) \land (\neg S \lor C) \ \ \ \ \ \textrm{by conditional law}\\ (\neg R\land \neg S) \lor C \ \ \ \ \textrm{by distributive law} I don't understand how it went from the second step to...
  38. F

    Which Formula for Friction Factor in Rough and Smooth Pipes?

    Homework Statement there are 2 formula of vont karman and prandit laws to find the friction factorfor rough pipe and smooth pipe , which formula should i use for this question? . P/ s : I'm asked to find the friction factor using the vont karman and prandit laws. Homework EquationsThe Attempt...
  39. A

    Newton's laws of motion -- masses on pulleys....

    Homework Statement Wasnt able to upload file, therefore an external link https://drive.google.com/file/d/0B0FIIKckKOcKWFcxcmtJRVRXZTA/view?usp=drivesdk A force F= mg is applied on C, all pullies are frictionless and we need to find the reading of the spring balance, basically the tension...
  40. B

    Proving the Exponent Laws in Group Theory

    Homework Statement Let ##x \in G## and ##a,b \in \mathbb{Z}^+## Prove that ##x^{a+b} = x^a x^b##. Homework EquationsThe Attempt at a Solution If I am not mistaken, we would have to do multiple induction on ##a## and ##b## for the statement/proposition ##P(a,b) : x^{a+b} = x^a x^b##. First we...
  41. A

    How to add eccentricity to Kepler's Laws in cartesian

    Hi, I'm currently making a three-body simulator and I'm trying to add the eccentricity to Kepler's Law to turn the circular orbits to more of a elliptical orbit? I'm using Newton's Law of Gravitational to plot the new positions. How would I add in the eccentricity to this equation? I'm...
  42. P

    Newton's laws -- Block sliding on a Prism

    Homework Statement All the surfaces shown in fig. are assumed to be frictionless. The block of mass m slides on the prism of mass M which in turn slides backwards on horizontal surface with acceleration of ao. Find the acceleration of smaller block with respect to prism. Homework...
  43. Holden Kenne

    B Understanding Newton's Laws of Motion: Exploring Errors and Contradictions

    Hi, I'm a frehshman in High school writing a paper about Isaac Newton. One of my paragraphs is about the laws of motion. I came across a tidbit of information - there are instances in which Newton's laws are not correct. One example I found was that, at speeds approaching that of light, an...
  44. S

    Forces that cause acceleration due to conservation laws

    I find difficulties in identify the forces acting behind the acceleration of objects that are considered consequence of conservation principles (for istance of KE and angular momentum). I'll make an example to explain. The same string-mass system is linked to a rod. In case (a) a force pull the...
  45. H

    I Are Physical Laws Truly Reversible?

    Must an initial state always be mapped onto exactly one final state and vice versa? Consider a slope that is shaped like a curvy "w". Releasing a ball from either end will result in the same final state where the ball is stationary at the highest point in the middle. So does it mean that...
  46. W

    Kirchoff's Laws Problem Current

    Homework Statement Given a battery with voltage 35.7 V and 4 Resistors (Top left with resistance 2R, and the 3 others each with resistance R) where R = 507 Ohms, what current would an ideal ammeter read in its current position? (Diagram attached) Homework Equations Kirchoff's Laws: KCL and...
  47. RoboNerd

    Question on Orbits and Kepler/Uni. Grav. Laws

    Homework Statement The picture has the problem question. OK. When the moon is at point B, the distance from the moon to the center of the planet is most nearly: A) (1/25) * rA B) (1/5) * rA C) (1/ sqrt(5) ) * rA D) rA E) sqrt(5) * rA. Homework Equations Newton's law of gravitation...
  48. V

    How Does Specular Reflection Support the Particle Theory of Light?

    I think this may have been done before. So people are aware of the geometry of reflection. If I go beyond, I try to say that if light can pump electrons, it is absorbed, if it merely polarizes, it gives rise to an alternating dipole supposed to be polarizing the region around in all directions...
  49. I

    Circular Motion/Newton's Laws-- Swinging a Pail

    Homework Statement You tie a cord to a pail of water, and you swing the pail in a vertical circle of radius 0.700 m What minimum speed must you give the pail at the highest point of the circle if no water is to spill from it? Homework EquationsThe Attempt at a Solution I got the correct answer...
  50. D

    How Does Adding a Cat Affect the Acceleration of a Block System?

    Homework Statement Consider the system shown in the figure (Figure 1) . Block A weighs 46.1 N and block B weighs 28.7 N . Once block B is set into downward motion, it descends at a constant speed. http://session.masteringphysics.com/problemAsset/1038576/6/YF-05-54.jpg A Calculate the...
Back
Top