Laws Definition and 1000 Threads

  1. cobalt124

    News European Court Ruling on UK Taxation Laws

    I think the non-payment of tax is a separate issue. How many people are non-taxpayers? Of more concern to me (going off topic a second) is this, care of our friends in the European Court: http://www.bbc.co.uk/news/uk-12022013
  2. M

    Newton's laws of motion discussion question

    this is from chapter 4 of university physics of young and freedman q19 why can it hurt your foot more to kick a big rock than a small pebble? must the big rock hurt more? explain? but I can't see the answer at all by just applying Newtons law in the scenario of the small pebble mp is small...
  3. A

    Laws of Physics may change across the Universe

    Interesting article in Newscientists, thought I'd start a discussion... http://www.newscientist.com/article/dn19429-laws-of-physics-may-change-across-the-universe.html
  4. F

    Newton's Laws, not sure which law this is, also FBD

    Homework Statement http://img576.imageshack.us/img576/5773/67450733.jpg Suppose three blocks as stacked as shown on a floor which I forgot to draw and assume it is frictionless. Draw a free-body diagram for each mass Now I know my FBD is wrong because it is a misconception of Newton's third...
  5. J

    How Do Dalton's Laws Help Calculate HCl Volume Needed in a Chemical Reaction?

    Homework Statement Given the following chemical reaction: Zn + HCl ----> ZnCl2 + H2(g) If you measured the total volume of collected gas over water at 20 Celsius to be 428 ml at a total pressure of 845 torr, how many milliliters of 2.6M HCl would be required to produce the correct amount of...
  6. P

    How to Find Coefficient of Kinetic Friction?

    Homework Statement A man is pulling a wagon up a 50° up a hill. His nephew of in unknown mass sits in the wagon. After pulling the wagon 30 meters up the incline, the man slips and falls releasing the wagon. The sled, starting from rest, slides down the incline. After traveling 30 meters the...
  7. D

    Calculating Orbital Velocity and Period Using Kepler's Laws

    Homework Statement A ship is in orbit 155 mi. above the earth, (a) what is its velocity? (b) How long will it take the ship to orbit the earth? Homework Equations v=(G*(m/r)).5, (2*PI*r)/T=v The Attempt at a Solution I added 155 mi to 3963 mi and got 4118 mi and that is about...
  8. A

    Vectors were introduced because they help physicists specify laws

    vectors were introduced because they help physicists specify laws without reference to any particular coordinate system...can we then say that position vector is really a vector because after all it depends on where we choose our origin?
  9. K

    Help with Real analysis proof about limit laws and functions

    Homework Statement Let f be a function let p /in R. Assume limx->p=L and L>0. Prove f(x)>L/2 The Attempt at a Solution Let f be a function let p /in R. Given that limx->pf(x)=L and L>0. Since L\neq0 Let \epsilon= |L|/2. Then given any \delta>0 and let p=0 we have |f(x)-L| = |0-L| =...
  10. P

    Newtons laws: Seem's simple but not for me

    Homework Statement given initial coordinates, r(0), r'(0) and F(r,r',t) find r(t) Homework Equations r''(t) = F(r(t), r'(t), t) / m The Attempt at a Solution have no idea where to start. some hint please, seem's pretty simple but not striking me.
  11. N

    Dot product, cross product, Newton's laws.

    My final for Physics is coming up and I really, really ****ed up in this class. I don't even know how to do dot products, cross products, or let alone Newton's laws. We applied Newton's laws to some pulley problems I think. I've been going to all the lectures but it just doesn't stick -- nothing...
  12. H

    Kepler's Laws and the Motion of Planets

    An artificial satellite circles the Earth in a circular orbit at a location where the acceleration due to gravity is 9.00 m/s^2. Determine the orbital period of the satellite.
  13. L

    How long does it take to move a box of books across the floor?

    Homework Statement A box of books weighing 329 N is shoved across the floor by a force of 484 N exerted downward at an angle of 32◦ below the hori- zontal. The acceleration of gravity is 9.81 m/s2 . If μk between the box and the floor is 0.57, how long does it take to move the box 3.66 m...
  14. M

    Newton's Laws, Kinematics, and Friction

    Homework Statement A student pushes horizontally northward on a 1.5 KG textbook initially at rest. The book is located 1.0m from the edge of a long table. the coefficient of static friction is 0.25, and the coefficient of kinect friction is 0.20. The applied force is just enough to get the...
  15. P

    The jumping skier (momentum, Newton's laws, energy)

    Homework Statement So, there is a skier (the blue recktangle) preparing to do a jump. There is no friction between the skier and the jumping board, and also no friction between the jumping board and the ground. Known values are: v0 - starting speed of the skier m2 - mas of the...
  16. A

    How Do You Calculate the Magnitude of the Second Force?

    Homework Statement Two forces act on a 39 kg mass to give it an acceleration of 26 m/s^2 in the positive x direction. If one of the forces acts in the negative y direction with a magnitude of 450 N, what is the magnitude of the second force. Answer in units of N. Homework Equations Fx:ma...
  17. J

    Is My Assumption of Conventional Current Direction Correct in this DC Circuit?

    Hello Folks, I have attached a DC circuit consisting of two opposing batteries and 3 resistors. The first step I took was to speculate on the direction of currents in both loops. I assumed the direction of conventional current for both loops, knowing full well that the maths will tell me...
  18. J

    Is De Morgan's Law Always True?

    In my textbook, the proof for demorgan's law, (AintersectionB)* = A*unionB* [*=complement] starts with,saying that for all x belongs to (AintersectionB)* , x is not a member of AunionB. But how can we say that, for example, if A = {1,2,3} and B = (2,3,4,5} and U = {1,2,3,4,5}...
  19. A

    Laws of conservation of mass (roller coaster) work and mechanical energy

    Homework Statement A 4.0 x 10^4kg roller coaster starts from rest at point A. Neglecting Friction, calculate its potential eneregy relative to the ground, its kinetic energy, and it's speed at points, B, C, and D. at point A : 54m B: 15m c:47m d:35mHomework Equations i got potential eneregy by...
  20. H

    Kirchoff Laws: Voltage & Current Detailed Help

    Pls anyone can Give me full detail of Kirchoff Law of Voltage and Current pls,,,
  21. M

    Kinematics/Newtons Laws Physics

    Homework Statement A 400 N force points due Northwest. a) In what direction must a 700 N force point so that the net force points due west? b) What is the magnitude of the net force? Homework Equations No Clue.. The Attempt at a Solution Answer says its.. a) [S66`W] b) 923 N...
  22. O

    How Do You Calculate the Coefficient of Kinetic Friction in a Pulley System?

    Homework Statement 2 objects with mass m1=10 and m2=5 are connected by a light string that passes over a frictionless pulley, they are set up so that m1 is sitting on the desk and m2 is attached to a pulley, is over he desk. if when the system starts from rest, m2 falls 1 meter in 1.2seconds...
  23. P

    Newton's Laws and finding magnitude

    An object of mass 1.25 kg on a flat surface has two forces acting on it, F1 and F2 in the horizantal direction. F1 acts in the positive direction, F2 acts in the negative direction. The magnitude of F1 is 26.75 N. The object moves strictly along the horizontal x-axis, which we choose as positive...
  24. A

    How Does Gravity Affect Friction in the Sticky-Shoe Lab?

    Homework Statement 1. what happened to the amount of friction between the surface and the shoe was the force of gravity was increased? 2. when a piece of paper was placed between the shoe and the surface(table), was more force, less force, or the same force needed to pull the shoe...
  25. A

    How Do You Calculate the Acceleration of a Toboggan with Given Forces?

    Homework Statement A toboggan with a mass of 15kg is being pulled with an applied force of 45 N at an angle of 40degrees to the horizontal. What is the acclecration if the force of friction opposing the motion is 28 N?Homework Equations Is this question related to the x and y component rules...
  26. P

    Newton's Laws and finding acceleration

    Homework Statement A brick of mass 1.0 kg slides down an ice roof inclined at 30 degrees with respect to the horizantal. If the brick starts from rest, how fast is it moving when it reaches the edge of the roof 0.90s later? Ignore friction Homework Equations Fnet = ma v2 = v1 +...
  27. M

    The accurateness of electricity laws

    Are the mathematical electrical laws as accurate as mechanics laws, if the input is perfect enough, or they're just good approximations?? I mean ohm's law and potential difference = electric field times length of wire (in wires), and alike laws.
  28. I

    Laws of physics may just be 'local by-laws'

    Although it is commonly accepted that physical laws and values of fundamental constants are the same throughout our universe, a recent finding, in which the fine-structure constant alpha has been found to vary by a small amount (1 part in 100,000) going from one end of the universe to another...
  29. A

    Wedge constant :- Newtons laws of motion

    what is wedge constant and where and how to use it?
  30. P

    Frictional Forces and Acceleration: Solving for Horizontal Component

    Homework Statement Two blocks are accelerated across a horizontal frictionless surface as shown. Frictional forces keep the two blocks from sliding relative to each other, and the two move with the same acceleration. F = 1.2 N and M = 1.0 kg Homework Equations what is the horizontal...
  31. T

    Passive forces and Newton's laws

    A block can move with constant velocity even though it has an applied force. Newton's first law is NOT violated. We were going over this in class today but I don't understand it, why is Newton's first law not violated? What applied force would you need to keep the block moving with a...
  32. A

    Optimizing Pulling Force: Solving for Theta and F in Newton's Laws

    A large block of mass M is going to be pulled with a constant velocity along a horizontal surface. The coefficient of friction between the surface and block is u. (1) Find the angle theta=theta_naught that the direction of pull shall make with the direction of motion for the pulling force to...
  33. S

    Newton's Laws of motion problem

    Homework Statement A block weighing 70.0 N rests on a plane inclined at 25.0° to the horizontal. A force F is applied to the object at 35.0° to the horizontal, pushing it upward on the plane. The coefficients of static and kinetic friction between the block and the plane are, respectively...
  34. J

    Newton's Laws Questions + Friction. Very tricky and help appreciated

    I AM NOT INTERESTED IN DIRECT ANSWERS! I'm just stuck on how to process these questions and just need a little guidance on what I'm doing wrong. I will be forever indebted and I am more interested in learning how to solve for these. Thank you! 1. A person weighing 0.9 kN rides in an...
  35. L

    Solving Gas Laws: 3H2 + N2 -> 2NH3 at 110 ATM

    It's a gas problem: 3 volumes N2 and 1 volume of H2 react at 344 degrees Celsius to form NH3. The equilibrium total pressure is 110 ATM and is 41.49% NH3 by volume. Find Kp assuming the gases behave ideally. So I started by assuming that I had 100L of gas. I worked the ICE table like so...
  36. J

    How do I find the necessary force to start a crate moving on a rough floor?

    Homework Statement To move a large crate across a rough floor, you push on it with a force F at an angle of theta=21.0 degrees below the horizontal. Find the force necessary to start the crate moving, given that the mass of the crate is 32.0 kg and the coefficient of static friction between...
  37. K

    Application of Gauss' Laws: Large area parallel plate capacitor

    Homework Statement The plates of a large area parallel plate capacitor of area A are separated by a short distance. The plates carry an equal but opposite charge \pm q. (a) What is the electric field strength E(q,A) inside the capacitor? (b) By how many percent does the electric field...
  38. H

    I don ` t understand Hawking` s answer to Why this particular set of laws? .

    I don ` t understand Hawking` s answer to "Why this particular set of laws?". I read the book the grand design by Stephen Hawking. The book at the beginning say it attempts to answer three questions. The questions are: 1."Why is there something rather than nothing?" 2."Why do we exist?" 3."Why...
  39. W

    Probability laws of quantum mechanics

    Im currently reading Entanglement by Amir D. Aczel and it talks about the Wu-Shaknov experiment of positronium emission where two particles annihilate each other and two high energy photons are emitted. It goes onto say that due to the probability laws of quantum mechanics, every so often three...
  40. C

    Mass hanging from the roof of a moving truck. Newtons laws.

    Homework Statement [PLAIN]http://img28.imageshack.us/img28/7341/capturehzm.jpg Homework Equations Fg=mg Ft=ma Ftx=Ftsin(22) Fty=Ftcos(22) Fg-Fty=? I realize this is probably required but I don't know where. The Attempt at a Solution I believe the acceleration the question is...
  41. A

    Need an explanation on how to do a question applying Newtons Laws

    Homework Statement A 2.0 kg mass , placed on a smooth, level table, is attached by a light string passing over a frictionless pulley to a 5.0 kg mass hanging freely over the edge of a table. Calculate... a) the tension in the string b) the acceleration of the 2.0 kg mass on the table.The answer...
  42. T

    Math Laws, Rules, and Precautions?

    Hey! I am curious to know if there is any book, site, or reference material that teaches you strictly on math laws. For example, they may give you formulas (like synthetic division).. and tell you that every time you use the restriction ( that happens to be a fraction, you must divide it...
  43. A

    One brick on another (friction, laws of Newton)

    Homework Statement [PLAIN]http://img693.imageshack.us/img693/8219/utennavnu.png Homework Equations n= normal force µ*n=friction F=ma. T = tension , mA = mass of A, mB mass of B The Attempt at a Solution a) Static friction should be used. Forces on brick A : x: T - µ*mg=0 y...
  44. B

    What is the force and acceleration in a conical pendulum?

    This homework is worth 5 percent of the total grade, so this shows that I am purely doing this for my own benefit. I'm struggling with this course, want to understand it, and will be taking more physics classes in the future college courses that I take. In conclusion to this, I ask that...
  45. R

    Electrical current & Kirchhoff’s laws

    Homework Statement [PLAIN]http://img84.imageshack.us/img84/3711/imagode.gif Consider the electrical circuit shown above. Using Kirchhoff’s Rules determine the currents I1 and I2. (Correct answers: I1=-0.727, I2 = 2.33) The Attempt at a Solution We can see from the network...
  46. E

    How to Solve Newton's Laws Problems for a Decelerating Particle?

    Homework Statement A particle is traveling in a straight line at a constant speed of 25.0 m/s. Suddenly, a constant force of 15.0 N acts on it, bringing it to a stop in a distance of 62.5 m. (a) What is the direction of the force? (b) Determine the time it takes for the particle to come...
  47. E

    Forces and Laws of Motion Problem

    Homework Statement A car with a mass of 1100 kg is being pulled by a tow truck exerts a 500 N force on the car and there is a 300 N friction force acting on the car. If the car starts at rest at time t=0, at what time has the truck moved 100 meters? Homework Equations x=v0t + 1/2 at2...
  48. E

    What is the explanation behind Newton's Laws?

    Homework Statement I need someone to help me fully understand Newton's Laws. I kinda get his second law, the sum of the forces equals mass times acceleration??, but yea. Homework Equations Newton's First Law Newton's Second Law...
  49. B

    Physical Chemistry-Gas Laws (Find R and M)

    Thanks ahead of time for any help! Homework Statement From Atkins Physical Chemistry text, 9th Edition: 1.7b) The following data has been obtained for oxygen gas at 273.15 K. Calculate the best value of the gas constant R from them and the best value of the molar mass of O2 (oxygen). p(in...
  50. R

    Newtons three laws of motion from a single rule.

    Dear all I have come with a simple idea to generate the three laws of motion of Newton and would love to hear comments on its correctness. Assume equal point masses: the rule says ' the displacement of one point mass must be balanced by an equal and opposite displacement of another'. Since all...
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