Constant Definition and 1000 Threads

  1. H

    Need a way to collect voltage from a constant source

    Say I have a constant source of 1 volt that will not diminish in volts during use and would like to collect that energy how would I do it. I have been trying To figure this out for the past month and source really appreciate some help. Thanks
  2. weezy

    Why Is My Normalization Constant Different from the Paper's Result?

    Homework Statement ## \psi(x) = N. (x^2 - l^2)^2 ## for ##|x| < l , 0 ## otherwise We have to find N such that this wavefunction is normalised.2. The attempt at a solution I tried expanding the ## (x^2 - l^2)^2 ## term inside the integral but this integral is extremely messy : ##...
  3. davidge

    B What Is the Significance of the Constant c in Wave Equations?

    For systems whose motion is discribed by the wave equation $$ \bigg(\frac{1}{c^2} \frac{\partial^2}{\partial t^2} - \vec{\nabla^2} \bigg)u \big(\vec{x},t \big) = 0$$ ##c## is the speed of light. It corresponds to different quantities depending on what the system under consideretion is. For...
  4. ciao_potter

    Maximum Distance Traveled with Constant Propulsion

    Lets say that we have a rocket positioned at a certain angle with respect to the horizontal. The rocket is fired, with a constant propulsion force of . Assume that the rocket has a constant mass of kg (the gas used to propel the rocket is negligibly small). What is the optimal angle with...
  5. R

    A The Lagrangian a function of 'v' only and proving v is constant

    Hi everyone. So I'm going through Landau/Lifshitz book on Mechanics and I read through a topic on inertial frames. So, because we are in an inertial frame, the Lagrangian ends up only being a function of the magnitude of the velocity only (v2) Now my question to you is, how does one prove that...
  6. T

    Calculating Acceleration: Solving SUVAT and a Constant Homework Statement

    Homework Statement A vehicle Accelerates from rest (a) and travels a certain distance s1 It then deccelerates (a) at a constant rate and travels a second distance s2 until it stops. If s2/s1 = K then what is the accleration (a) of the vehicle. Homework Equations v=u+at s=ut+1/2at^2...
  7. U

    Pressure dependence of the equilibrium constant for an ideal gas

    I read in some scripts that equilibrium constant for an ideal gas is not a function of pressure: But that is not generally true! Since: $$\left (\frac{\partial \Delta_{R} G}{\partial p} \right )_{T,\vec{n}}=\Delta_{R} V$$ and $$\Delta_{R} G^{0}=-RT\cdot \ln K$$ it should be: $$\left...
  8. hilbert2

    A Constant Solutions of Real Scalar Field

    Suppose I have a self interacting real scalar field ##\phi## with equation of motion ##\partial^i \partial_i \phi + m^2 \phi = -A \phi^2 - B\phi^3##, and I attempt to find constant solutions ##\phi (x,t) = C## for it. The trivial solution is the zero solution ##\phi (x,t) = 0##, but there can...
  9. A

    Why Earth has constant acceleration?

    according to f=GMm/r^2 if force changes based on a distance between 2 objects, so during free fall object is constantly changing its distance, so does that mean the Earth is exerting a non-constant force on that object? if that was right, why's that object accelerate at a constant rate of...
  10. Akwinder Singh Mander

    I Is the speed of light constant?

    It is said that due to the expansion of the universe, there are some distant galaxies that are moving away from us faster than the speed of light. They can't actually move faster than speed of light itself, because the law of physics over there are supposed to be the same as the law of physics...
  11. J

    Find constant when velocity is proportional to time

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] I am having difficulty understanding the question statement . I do not understand how can body come to rest when velocity is directly proportional to time .As time progresses , velocity increases . Could someone help me...
  12. chopnhack

    Gas at a constant pressure: using Cv.dT correctly

    Hello, my questions is not so much homework, but a request for a definition. When we use Cv*dT to solve for dU (internal energy) in a constant pressure example, what is the order of the temperatures entered into dT? Is one to assume its final temp minus initial temp? I ask because it leads to...
  13. N

    B Would All Observers See a Warp Drive Spaceship at Constant Speed?

    If you were in a warp drive spaceship traveling at say 2c. Would all observers see your ship traveling at 2c?
  14. Drakkith

    I When is a Constant a Solution to a Differential Equation

    I've run across several instances while doing homework where a question will have two solutions. One will be an equation, and the 2nd will be a constant (usually zero). I can't figure out why this constant is a solution though. For example, take the following differential equation...
  15. X

    B C as Energy Conversion Constant: Conservation Law Explained

    I was thinking about the law of conservation of energy, states that energy can neither be created nor destroyed. Then I thought about it more broadly, it actually states that the universe was created with a fixed amount of energy (and this energy only transforms from one form to another) And...
  16. A

    A Cosmological constant in the semiclassical limit of quantum gravity

    Why is it the case that, in a semiclassical description of the Einstein-Hilbert action, the cosmological constant is small in Planck units? Why does this mean that $$\ell \gg G$$ for ##\Lambda = - 1/\ell^{2}##?
  17. V

    Does V0 affect acceleration under constant Force?

    Homework Statement A block of mass M = 10 kg is sitting on the table as shwoin Figure above. There is friction between the block and the table, the coefficient of friction is u = 0.1. The block has initial velocity V, and a constant forceF is applied to the black as showing Figure above. A)...
  18. H

    How to find a constant in this quadratic equation?

    Homework Statement Homework Equations for equation which has 2 different solutions, D >0 The Attempt at a Solution (1)[/B] D > 0 b^2 - 4ac > 0 3 - 4root2.k > 0 k < 3 / ( 4root 2 ) k < ( 3 root 2 ) /8 has solution of sin tetha and cos tetha sin 0 = 0, cos 0 = 1. when x = 0, and x = 1 -->...
  19. A

    Forces, 3 masses, 2 by Tension, constant A

    Hello, This is an advanced forces problem from introductory Calculus with Physics. I have mostly solved the problem I am posting here but am just missing a force on my diagram somewhere. M. The jpeg below "MassCartTheProblem_1.jpg" shows a picture of the situation and the goal is to find the...
  20. A

    How to find the torque constant of BLDC motor?

    Hello Friends, I have used in-wheel BLDC motor for my experiment. In this type of motor BLDC motor inbuilt on wheel. This wheel is a part of electric scooter. I wated to find the value of torque constant and back emf constant. Also how to measure torque for a selected current. Please help me...
  21. Chris Miller

    B Hubble's constant and Minkowski spacetime

    If Hubble's constant = 160,000 m/sec/million light years and c = 299,792,458 m/sec, then shouldn't any two points in the universe farther than about 1,873,000,000 light years apart be expanding away from each other faster than c? Since light from sources much farther than this has reached us...
  22. M

    MHB Finding the Constant a for a Given Point on a Linear Equation

    You are given an equation and a point. In each case, find the value of the constant a so that the graph of the equation passes through the given point. y = -5x - a; (-4, 1) Solution: Let x = -4 and y = 1 y = -5x - a 1 = -5(-4) - a 1 = 20 - a 1 - 20 = - a -19 = -a -19/-1 = a 19 = a...
  23. G

    I Dimensionless coupling constant of gravity

    In analogy to the fine structure constant, the dimensionless coupling constant of gravity is defined as some reference mass divided by the Planck mass, squared. But what is the reference mass?? I have read thread...
  24. D

    I Lorentz transformation of the Gravitational constant

    Since force is transformed via: F'x= Fx ; F'y= Fy/ ϒ; F'z=Fz/ ϒ (F' is the force related to the moving frame, F is the force on the rest frame and ϒ=1/√1-v2/c2 ).I expect that G (Gravitational constant) will be transformed between moving and rest frame in order to satisfy force transformation...
  25. maistral

    Implementing barrier/penalty functions to *Equality* constant

    Hi. I seem to have forgotten how to implement equality constraints to barrier NLPs and quadratic NLPs. Say for example I have this problem: Max Z = x12 + 2 x22 ST: x12 + x22 ≤ 1 x1+ x2 ≤ 1 The unconstrained problem (quadratic penalty - correct me if I'm wrong) then becomes Z = - x12 - 2 x22...
  26. U

    I Cosmological constant estimation in QFT

    My question is about the interpretation of the large estimated value. In QM we are supposed to think in terms of measurement results and not of ontological properties. So, if QFT predicts a large vacuum energy what is the correct approach? 1. The predicted value is the result you get if you...
  27. Demystifier

    A Why isn't cosmological constant a mass of the graviton?

    The Lagrangian density for cosmological constant is $${\cal L} = \sqrt{g}\Lambda$$ Let us write, schematically, $$g=\eta+h$$ where ##\eta## is the flat Minkowski metric and ##h## is the spin-2 field. Expanding the square root for small ##h## we get something like $${\cal L} = \Lambda + h\Lambda...
  28. A

    Moseley's law and the determination of the screening constant

    Homework Statement The aim of a laboratory course was to measure the x-ray fluorescene spectra of 20 metallic samples. By comparison of the peaks in the energy spectra with known electronic transitions (e.g. ##K_α## of ##Cu##) the materials were identified. After that, Moseley's law $$...
  29. Mr Real

    I Constant raised to complex numbers

    It's not a homework question. I just thought up a method of finding answers to problems where a number is raised to a complex number and I need to know if I am right. If we have to find e^(i), can we do it by; first squaring it to get, e^(-1) which is 1/e and then taking its square root to get...
  30. T

    Is the water pressure below ocean waves constant?

    If you are stationary say 10m below the ocean surface does the water pressure at your location vary with the waves. For example: When a wave crest is above you than means perhaps 12m of water is above you. Then a few seconds later a trough is above you so only 8m of water is above you. So you...
  31. W

    I Cosmological constant problem, interesting solution?

    Som news outlets are reporting a potential solution to the cosmological constant problem: https://arxiv.org/pdf/1703.00543.pdf opinions on this paper are much appreciated.
  32. S

    A Variation of Hubble constant in cosmological time

    Is the Hubble constant decreasing over cosmological timescales?
  33. B

    I Humidity when T is not constant in space

    Hi all! How is humidity related to temperature in a system where temperature is constant in time but not in space? As an example: If we have humid air trapped between two parallel walls with T1 and T2 respectively, how does humidity behave along the line from one to the other wall? Is absolute...
  34. T

    I Is nuclear decay probability always constant?

    I have heard that the probability of an unstable nucleus decaying is always constant. Is there any way to change this probability?
  35. A

    B How are activity and decay constant different?

    What's the difference between activity of a radioactive sample and the decay constant. Both are measured in second inverse. Please distinguish among the two?
  36. Physics Dad

    Calculating Spring Constant From Plot of T^2 versus r^2

    Homework Statement Hi, I recently performed a lab experiment for calculating the moment of inertia and spring constant of a couple of equal masses on a steel rod. I had to do this experiment at the exact same time as performing another experiment so I was unable to perform any calculations in...
  37. S

    Heat capacity at constant volume and density

    Hello! I encountered in a problem the terms heat capacity at constant volume and density (##n##) and heat capacity at constant chemical potential (##\mu##) and volume and I need to prove a relation between them. What is their definition? I thought that for the first one it would be...
  38. Emmanuel_Euler

    Dielectric Constant Vs Temperature Vs Polarity

    please explain the concept of dielectric constant in the simplest CHEMICAL terms possible. why does it decrease when the temperature increases? and why does it increase when the polarity increases? please keep it simple and brief.
  39. Feodalherren

    Frictionless ring sliding on circle in constant acceleration

    Homework Statement A box is sliding with constant acceleration a to the right. Inside the box there is a quarter of a circle upon which a frictionless ring can slide. Find the angle theta in terms of the other given variables. Picture in solution Homework Equations F=ma, etc. basic stuff...
  40. Buggsy GC

    How do i find the spring constant for a rope torsion spring

    I have built a torsion wheel catapult (Mangonel) for an assignment,and I need to do some theoretical calculations about the displacement, velocity and time of the projectile, the problem is I don't know how to calculate the spring constant without the displacement of the spring (x) and i don't...
  41. S

    A Dependence of entropy and temperature on Planck's constant

    Consider the dependence of entropy and of temperature on the reduced Planck's constant (taken from page 23 of Thomas Hartman's lecture notes(http://www.hartmanhep.net/topics2015/) on Quantum Gravity): $$S \propto \hbar, \qquad \qquad T \propto \hbar.$$ I do not quite see how entropy can depend...
  42. M

    Constant frequency of light and connection to QM

    Could someone provide a good explanation as to why light's frequency doesn't change under refraction? The textbook I'm using gave us a two step derivation and I don't really feel like it did a proper job in explaining anything (it's Haliday). Also, a slightly *crackpot* follow up question -...
  43. S

    I Would we observe a changing Planck's constant?

    If Planck's constant is changing, how slowly would it need to change before we could observe that something was going on? And if changes were discrete, how large quanta would it take? (for us to observe the jumps) And a follow-up question: If there was another universe here, running a different...
  44. B

    Is the torque constant of a DC motor the same regardless of voltage?

    Hi, we know that the speed varies inversely with the torque. The more the torque, the lower the speed. From torque-speed curve, we can calculate the slope. When the applied voltage increases, the straight line shifts upward while when the voltage decreases, the straight line shifts down. How...
  45. Ryaners

    Finding order of reaction & rate constant

    I'm trying to solve one of the problems in my textbook (Atkins Physical Chemistry) and I just can't get it out. Here's the problem: "The data below apply to the formation of urea from ammonium cyanate. Initially 22.9g of ammonium cyanate was dissolved in enough water to prepare 1.00 dm3 of...
  46. B

    I Gravity: Constant on Earth? | Is It Divisible?

    If the Earth were divided into 4 sections and separated far enough that they have no gravitational pull on each other, would the gravity on each section be 25% of the current gravity on Earth?
  47. L

    Prof. Shankar's (Phy I) Constant Motion Exercise 3 Question

    Hello everyone, this is my first post, so go easy on me! Thank you to those who are able to help. 1. Homework Statement The problem is taken from Professor Shankar's Fundamentals of Physics exercises (Problem 3). Romeo is at x = 0 m at t = 0 s when he sees Juliet at x = 6 m Romeo begins...
  48. Puff Cube

    Object moving upwards by constant force away from planet

    Homework Statement Suppose there is an object that is a distance ##r_0## from the center of a planet that is nearby (the object is outside the surface of the planet). Let ## r ## represent the distance from the object to the planet's center. Let ## t ## represent time. The object, which is...
  49. Simon Peach

    B The Speed of Light and Time: A Constant Debate

    The speed of light is constant, in what ever direction, that's not disputed. Now in relativity that as I understand light speed constant C is bound up with time, eg faster you go faster time pass for an outside observer but stays the same in your field of reference. Or to put it another way the...
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