Laws Definition and 1000 Threads

  1. bbbl67

    Kepler's Laws, two large bodies

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Here is something that some one asked me, as their homework question, and it stumped me. A star is seen orbiting a black hole. The black hole's mass is 6.0E30 kg (approx, 3 solar masses). The...
  2. Ameer Bux

    How Can I Ace My Physics Test on Newton's Laws and Gravitation?

    Hi guys. I am planning to get 100 percent for my upcoming physics test in two days time. I am i grade 11. The test is based on Newtons 3 laws and universal law of gravitation. What are some of the best tips you can offer from your experience to help me achieve my goal?
  3. P

    I Understanding Hamiltonian Conservation Laws

    I'm a little confused about the hamiltonian. Once you have the hamiltonian how can you find conserved quantities. I understand that if it has no explicit dependence on time then the hamiltonian itself is conserved, but how would you get specific conservation laws from this? Many thanks
  4. Z

    Derivation of Wien's+Reyleigh-Jean's Laws from Planck's Law

    Homework Statement After reading the forum stickies I'm not entirely sure where to put this question since it involves using math to solve a question, but is informally stated and isn't a book problem, either-I just started reading Fong's Elementary Quantum Mechanics, and in the first few...
  5. J

    Estimating Star Counts from Density Laws

    Homework Statement (This is a long problem but I think the question is not hard.) Determining the star density from star counts is tough, but estimating counts from a density law is simpler. In practice, this method of fit-ting observed number counts to an assumed density law is becoming a...
  6. emeriska

    LRC equation using Poynting theorem and conservation laws

    Homework Statement We have an ordinary LRC circuit with inductance L, capacitance C and resistance R with an oscillating voltage with low frequency (U^e). Using the energy conservation law and Poynting's theorem, find the differential equation: $$L \frac{\partial ^2}{\partial t^2}I + R...
  7. Cosmophile

    Are Newton's Laws Redundant or Fundamental?

    Hey, all. I've been studying Newton's Laws and I can't help but to feel a bit uneasy as I inspect them. From my point of view, they seem to be tautological. I'll refer to Newton's First Law as N1L, and similarly for the other two Right off the bat, I suppose I don't see any reason for N1L to...
  8. 1729

    Problem involving gas laws and hydrostatics

    Homework Statement A glass tube filled with air at room temperature is 1.54m long. The tube is closed on one end, and open on the other. When submerging the open end in water, the water in the tube rises by 0.14m. How much of the tube is above the water's surface? The correct answer is 0.40m...
  9. **Mariam**

    Kepler's laws, universal gravitation mcq doubt

    Homework Statement http://[url=http://postimg.org/image/f7e6kp0xv/][PLAIN]http://s21.postimg.org/f7e6kp0xv/image.jpg Homework Equations Kepler's laws The Attempt at a Solution I thought the answer will be C : I and II But the solution written (it was my friends book) is B, which is correct?
  10. J

    The Laws and Rules of Emergence in Spacetime and Matter Fields

    Are their specific laws or rules in emergence? For example, temperature is emergence from the underlying particles. Superconductivity is emergence from the cooper pairs. It seems you can turn off emergence by say increasing the temperature to disable the cooper pairs. In temperature, how do you...
  11. W

    Does Increasing Molecules in a Constant Temperature Container Affect Pressure?

    Homework Statement If number of molecules in a closed container increases and it is kept at a constant tempurature, what happens to the pressure? I was confused because I thought if you add molecules the temputature would go up so keeping temputature a constant would have no affect on the...
  12. T

    MHB Laws of Exponents: Understand What Your Textbook Is Saying

    In my textbook, it makes the leap from $2(2^{n + 1}) = 2^{n + 2}$ citing the laws of exponents. I'm not sure which law of exponents it is referring to. Thanks
  13. denisaf

    Laws of Mass Dynamics: Conservation & Transformation

    The laws of thermodynamics deal with the irreversible flow of energy. Conservation of energy is the first law and increasing entropy (disorder) in an energy flow is the second. The conservation of mass is the equivalent first law for matter. It is commonly recognized. But what about the...
  14. A

    R136a defies Laws of Stellar Evolution

    At 265 SM, and age 1.7 Million years, at 163,000 Light Years Away in the R136 cluster, is R136a. But, it shouldn't be alive now. It should have exploded given the model of Solar Mass Evolution at 200,000-375,000 Years old of age. It's in it's Wolf-Rayet phrase, but it still shouldn't be alive...
  15. mcdavid&goliath

    Newton's laws multiple choice question

    Homework Statement A book of mass m is sitting on a table of mass M. Which of the following statements regarding Newton's Laws of motion is true? (a) Newton's Third Law says that the magnitude of the normal force from the table on the book is equal to mg. (b) Newton's Second Law says that the...
  16. A

    Question based on laws of motion (inclined motion )

    Homework Statement what is the value of F needed so that block begins to move upward on frictionles incline plane . Homework EquationsThe Attempt at a Solution i made an attemp and got the answer - Mgtan(thetta) but the real answer is - mgtan(thetta/2)
  17. S

    Newton's Laws: Impact, Orbit & Weight

    1. Which will have the greater force during impact; a bumble bee being hit by a train or a train being hit by a bumble bee? (Hint: Newton’s Three Laws of Motion) 1. What is the centripetal force that holds the Earth in orbit around the sun? 1. How much does a 76.0 kg person weigh on Earth in...
  18. G

    What is the accelerating force of a bullet in a 10cm gun barrel?

    Homework Statement [/B]A 10g bullet accelerates from rest to 500m/s in a gun barrel of length 10cm. Find the accelerating force (assuming it is constant).Homework Equations F=ma, v^2=vo^2+2a(x-xo)? The Attempt at a Solution I tried using F=ma, but it does not equal the answer in the back of...
  19. F

    The Role of Theories, Models, and Laws in the Scientific Process

    What role do theories, models, and laws play in the scientific process? Is there a clear dividing line between a theory and a law? Are models used in both theories and laws? All theories and laws? Do our best current models perfectly represent reality to the best of our knowledge, or are they a...
  20. N

    Conservation laws with Killing fields

    Hi, In general relativity we have no general conservation of energy and momentum. But if there exists a Killing-field we can show that this leads to a symmetry in spacetime and so to a conserved quantity. Thats what the mathematic tells us. But I don't understand what's the meaning of an...
  21. entropy1

    Multiple universes, measurement and laws of nature

    Considering the multiple universe view, if a measurement (or something else) makes visible which universe we are in, is it then also possible we find ourselves in one with (slightly) different laws of nature?
  22. GymGuy

    Solve Kirchhoff's Laws for Currents and Power Dissipation in a 3-Loop Circuit

    Homework Statement [/B] In the circuit shown below if Vs = 5V, use Kirchhoff’s Laws to determine the currents i1, i2, i3 and the source current is. Calculate the power dissipated by the resistors in this circuit. Confirm that the power dissipated by the resistors is the same as the power...
  23. sidt36

    Mastering Newton's Laws for 9th Grade Talent Exam: Overcoming FBD Problems

    I have been preparing for a 9 Th grade talent exam and i can get my head around this problem I keep getting the same answer 5, i used fbd The answer is 7 ; help me out where am i wrong
  24. M

    Laws of Exponents: Solve Math Homework Questions

    Hello, this isn't really a physics question but I'm getting pretty desperate and you guys have always been able to help me out before :) 1. Homework Statement http://imgur.com/mYtJDLI Homework Equations I believe I'm suppose to use the Laws of Exponents. For the first set possibly but not...
  25. toboldlygo

    Best source(s) to get a great grasp on forces/Newton's laws?

    So, we're learning about forces and Newton's laws in class, and my professor zips through the material without really explaining anything. I'm having the most trouble understanding f_net=ma (specifically, how that can be used in a free body diagram) and how third-law pairs fit into a free body...
  26. N

    Clarification of the laws applied

    I am a first year student and i am required to build one thing based on one physics law . if i build a rubber band powered airplane , what laws should i say it applies? and what about rubber band powered car??
  27. O

    Looking for worksheet (Newton's laws)

    Hey, Anyone know any good workshetts, pdf wise or a document with good questions about Newtons laws. What i mostly look for is, Incline plane questions, atwood machine questions with pulleys in different ways, half atwood machine questions. Etc. Very classical problems. Glad if U could help...
  28. bcrowell

    A Laws of physics in noninertial frames

    In a previous thread, the OP asked for answers at the "I" (i.e., undergraduate) level to the following question: S/he received a variety of contradictory answers, and the discussion may have been hindered by attempts to present more sophisticated mathematical ideas as the appropriate level...
  29. AveryB

    Help with Newtons laws of motion and force?

    If anyone could tell me how to answer these questions that would be fantastic. Thank you so much! 1. A box that weighs 66.2 N on Jupiter is taken to Pluto. The weight of the box on Pluto will be ____. (acceleration on pluto is 0.42) Would you find the mass first? 2. The hand in the image...
  30. P

    How Do De Morgan's Laws Apply to Set Theory Proofs?

    Homework Statement Prove ##A\setminus(B\cap C)=(A\setminus B)\cup(A\setminus C)## Homework Equations 3. The Attempt at a Solution [/B] We will show that every element in ##A\setminus(B\cap C)## is contained in ##(A\setminus B)## or ##(A\setminus C)##. If ##x\in A\setminus (B\cup C)## then...
  31. Einstein's Cat

    Is there a unified equation for the forces of gravity and electromagnetism?

    Is there an equation which combines Newton's equation of calculating the gravitational force between two masses with that of Coulomb's equation of describing the electromagnetic force between two particles? In other words, does an equation exist which describes the relationship between mass and...
  32. DylanC.

    My Physics Professor says Newton's laws are wrong?

    My Physics Professor from my Physics 1 class says Newtons laws are wrong? Don't get me wrong, but he is a amazing physics professor! One that does not talk to you as if you are dumb or as if he is better than anyone! I love physics and I'm hoping to go into physics engineering, but that's not...
  33. B

    Newtons Laws car deacceleration

    Homework Statement A 1900 kg car moves along a horizontal road at speed v0 = 23.6 m/s. The road is wet, so the static friction coefficient between the tires and the road is only μs = 0.218 and the kinetic friction coefficient is even lower, μk = 0.1526. The acceleration of gravity is 9.8 m/s2...
  34. mokeejoe5

    Relativity and conservation laws

    Does the relativity of simultaneity imply the impossibility of non local conservation laws?
  35. P

    Exponent Laws Related Homework Question

    Homework Statement For which non-zero value of x is the equation -x^ -4 = (-x)^ -4 true? Explain. Homework Equations None. Other than applicable exponent laws. The Attempt at a Solution I know how to use the guess and check method. But I was wondering how to reach the answer faster and how...
  36. S

    Newton's laws of motion problem -- Knife penetrating cardboard

    An open knife edge of mass 200 g is dropped from height 5 m on a cardboard. If the knife edge penetrates distance 2 m into the cardboard, the average resistance offered by the cardboard to the knife edge is:
  37. klotza

    Scaling Laws and the Speed of Animals - Comments

    klotza submitted a new PF Insights post Scaling Laws and the Speed of Animals Continue reading the Original PF Insights Post.
  38. F

    Using different limit laws give different answer?

    Hi, My instructor gave us a challenge problem to solve in limits: ##\lim _{ x\rightarrow \infty }{ \left[ { x }^{ 2 }\left( 1-\cos { \frac { 5.1 }{ x } } \right) \right] } ## Note that we did not take Hospital's rule yet so we couldn't have used it. Now my first thought was to use the...
  39. Priyadarshini

    Gas Laws - What is the final pressure in the system?

    Homework Statement Two glass vessels M and N are connected by a closed valve. M contains helium at 20 °C at a pressure of 1 × 10^5 Pa. N has been evacuated, and has three times the volume of M. In an experiment, the valve is opened and the temperature of the whole apparatus is raised to 100...
  40. vinicius0197

    Deducing Kepler's second law from Newton's laws?

    I've searched a little bit and found that I can derive kepler's third law from Newton's law of gravitation. That's okay. But I want to deduce kepler's second law too: "An imaginary line joining a planet and the sun sweeps out an equal area of space in equal amounts of time". I know it's possible...
  41. A

    Center of mass and Newton's laws of motion

    Homework Statement two particles of 2 kg and 3 kg are at rest . a 6 N force is exerted on the 3 kg particle at t=0. what is the speed of the center of mass at t=5s? Homework Equations F=ma v=u+atThe Attempt at a Solution first i applied f=ma to the 3 kg object and got 2 as the accn. And...
  42. MARK 42

    How to Determine the Upward Acceleration of M in the Pulley System?

    In the arrangement shown in the figure, find the acceleration of M in upward direction. The pulleys are light. The strings are mass less and friction between the string and the pulleys is negligible. The options are given. The final answer is (B) and this was the solution: I don't...
  43. A

    Force and Laws of motion Text Book

    What is the best way to make a 9th grader understand the concept of force and laws of motion. Also please refer a book where he can get a good practice to solve force numericals. Please mention the ISBN code of the book also. Thanks a lot
  44. pinochet

    Acceleration of gravity and Newton's laws of motion

    hello I've just started learning physics my question is why do force increase while falling and stay constant while on the ground.i know force is increasing because in free fall things accelerate which according to Newton first law force must also go up. the force of gravity of Earth is 9.8N...
  45. H

    Prove that a finite set with cancellation laws is a group

    If G is a finite set closed under an associative operation such that ax = ay forces x = y and ua = wa forces u = w, for every a, x, y, u, w ##\in## G, prove that G is a group. What I attempted: If we can prove that for every x ##\in## G, x##^{-1}## is also ##\in## G, then by the closure of the...
  46. wheels123

    Can you explain the lever using Newton's Laws?

    I have always thought that all of "Classical Mechanics" can be explained with Newton's Laws and a few force equations (e.g., gravitational and Coulomb). In particular, the concepts of energy and torque are convenient but not necessary. If this is true, then can you explain with Newton's Laws -...
  47. C

    Basic Newton's Laws and Applied Force: 3 boxes

    Homework Statement Three boxes are in contact with each other on a frictionless horizontal surface as shown. The masses of the boxes are m1 = 10 kg, m2 = 20 kg, and m3 = 30 kg. A horizontal force F = 90 N is applied to m1. Calculate: a. the acceleration of the three boxes. b. the net force on...
  48. A

    Thermionics disobeying laws of thermodynamics

    Hi there, Now this goes against everything I know as a physicist, but I can't get my head around how thermionics behave when you have an emitter at slightly lower temperature but much lower work function, and a collector at higher temperature and higher work function, so that thermionic current...
  49. Stephanus

    Understanding the Laws of Physics in SR: Questions & Answers

    Dear PF Forum, Before I go further, I'm stuck and need clarification. Two postulates of SR 2. the velocity of light is the same for all inertial observers. Okay..., this one I can understand, at least can grasp. 1. the laws of physics are the same in all inertial frames of reference; What laws...
  50. Buzz Bloom

    Neutrinos and Conservation Laws

    I am confused about the current physics regarding neutrinos and implications about the conservation laws of mass-energy and linear momentum. I have read the threads listed for similar discussions, including, "How does conservation of energy/mass apply to neutrinos?", and none of them seem to...
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