Derive Definition and 620 Threads

  1. F

    Do you know how to derive the General Theory of Relativity?

    I am trying to get the coeficient gamma=1/squareroot(1-(v/c)2) I am trying to do this by my own knowledge starting from scratch. Can someone give me the first step? I want to see if i can get there but i just need a hint i am not sure on where to start Thankyou very much, Fox
  2. L

    Deriving Final Mass, Velocity, Radius of Merged Isothermal Sphere

    Homework Statement Now imagine the two spheres fall toward each other and merge, and that after some time, they equilibrate and end up as a single isothermal sphere. Use con- servation of mass, energy, and the virial theorem, to derive the following (and explain your results in words): the...
  3. F

    How to derive tan(2x) using the definition of the derivative ?

    Homework Statement Can someone please derive tan(2x) using the definition of the derivative? Homework Equations The Attempt at a Solution I've tried to expand it but I couldn't get anywhere with it thank you,
  4. B

    Implicitly find the second derivative of x^2- y^3= 3

    Homework Statement Find \frac{d^2y}{dx^2} of the following equation: x^2-y^3=3Homework Equations Quotient Rule: \frac{d}{dx}(\frac{f(x)}{g(x)})=\frac{g(x)\cdot f^{'}(x)-f(x)\cdot g^{'}(x)}{g^2(x)} The Attempt at a Solution I solved for the first derivative: \frac{2x}{3y^2} But I'm stuck as...
  5. G

    Derive that the lagrangian in classical phyics is L=T-V

    Hey, can somebody show me how to derive that the lagrangian in classical phyics is L=T-V i have seen this formula so many times, but i have no idea where it really comes from?
  6. K

    How to derive the spherical coordinate form for Laplacian

    Homework Statement \Delta f = \frac{1}{{r^2 }}\frac{\partial }{{\partial r}}\left( {r^2 \frac{{\partial f}}{{\partial r}}} \right) + \frac{1}{{r^2 \sin \phi }}\frac{\partial }{{\partial \phi }}\left( {\sin \phi \frac{{\partial f}}{{\partial \phi }}} \right) + \frac{1}{{r^2 \sin ^2 \phi...
  7. J

    Trying to derive a group velocity equation?

    hi, I am trying to derive the group velocity equation (actually its inverse): \frac{1}{v_g} = \frac{1}{c}(n(\lambda) - \lambda\frac{dn}{d\lambda}) where n is the refractive index and depends on the light's wavelength. I have started by saying that if v_g = \frac{\partial\omega}{\partial...
  8. S

    Derive Equations for Bungee Jumper

    Homework Statement [PLAIN]http://img697.imageshack.us/img697/6702/bungee.png Derive the equations of the motion for the jumper. Consider only the vertical motion of the jumper. (g = 9.81 m/s^2) Homework Equations Straing = (Stated Above) Strain Rate = v / lo = v/25 F = -kx...
  9. S

    Derive time for relativity (i know how but not sure what to do i got a idea

    Homework Statement Homework Equations equation 37.23 37.30 are the following 37.23 x'=gama(x-vt) x= gamma(x'+vt') t=gamma(t-vx/c2) t'=gamma(t'+vx'/c2) 37.30 u'=(u-v)/(1-uv/c2) u=(u'+v)/(1+uv/c2) The Attempt at a Solution i tried the following... since d=vt... i...
  10. M

    Use work/energy throem to derive an expression for moment of inertia?

    Homework Statement Today I had a physics lab. It involved a hanging mass on a string that hung off the table. It went through a pulley and the string was then spooled around a rotating spool on the table. We first measure the radius of the spool. Then we figured out the mass it took to...
  11. M

    Derive a formula for momentum in terms of kinetic energy

    Homework Statement Using: particle velocity, beta particle momentum, p total energy, E Lorentz factor, gamma kinetic energy, KE Derive an equation for momentum as a function of kinetic energy. The functions have to depend either on the variable in the bracket, p(KE), or on a...
  12. G

    How to derive XOR from only NOR gates

    Hi, Through some searching and guessing with LogiSim I was able to see how to build a XOR gate from only NOR gates. I would like to know what the process for deriving this would look like. Right now I am lost as to how to proceed given that the NOR function is A'B' and XOR is AB' + A'B. How...
  13. A

    Blackbody radiation - derive expression for T

    Homework Statement Derive an expression for the temperature of an ideal blackbody so that its radiated light at the peak intensity wavelength has exactly enough energy to excite the ground state to fourth excited state. Homework Equations I = σ*T4 λm*T = 2.9 * 10-3 m * K E = hf = hc/λ...
  14. A

    Derive Quotient Rule: Find the Mistake

    Homework Statement derive f(x)=x2+2x+1/ x2-3x+2The Attempt at a Solution (x2-3x+2)(d/dx)(x2+2x+1)-(x2+2x+1)(d/dx)(x2-3x+2)/(x2-3x+2)2 =(x2-3x+2)(2x+2)-(x2+2x+1)(2x-3) =(2x3-4x2-2x+4)-(2x3+x2-4x-3) =5x2+2x+7/(x2-3x+2)2 that's what I'm getting... but according to the online derivative...
  15. P

    What Is the Key Step Missing in Deriving Wirtinger Derivatives?

    Let \bar{z} = x+iy. We are given that x = \frac{z+\bar{z}}{2} & y = \frac{z-\bar{z}}{2i}. We are trying to derive \partial F/\partial\bar{z} = 1/2(\partial F/ \partial x + i \partial F/ \partial y), where F(x,y) is some function of two real variables. Using the chain rule I get \partial...
  16. R

    Derive y as function of time in relation to terminal velocity

    Homework Statement Integrate v_{y} = v_{t} (1 - e^{-(\frac{k}{m})t})) to get y as a function of time. Homework Equations y = v_{t}(t - \frac{m}{k} (1 - e^{-(\frac{k}{m})t}))) is the solution. v_{t}=\frac{mg}{k} The Attempt at a Solution Well, when I integrate I get the following: y =...
  17. D

    Why derive electric field produced by a rod?

    Is there a practical utility to derive the electric field produced by a charged rod (and the 1/r dependence at great distance)? I know it can be useful to derive the electric field produced by a large plate since you can then show that the field between close parallel plates that are oppositely...
  18. J

    Derive Electric Field of Cylinder Via Gauss' Law

    1. An infinitely long cylinder of radius R contains a uniform charge density Rho. Calculate the electric field using Gauss' law for r> R and R>r 3. I attached a pdf with my attempt at r>R. My answer doesn't agree with those given...
  19. Z

    Deriving the Equation for Final Velocity Using Kinematic Equations

    Homework Statement I wanted to know how this equation is derived. Thanks. Homework Equations {v_{f}}^2 = {v_{i}}^2 + 2a\Delta d The Attempt at a Solution v_{f} - v_{i} = \frac {\Delta d a} {\Delta v}
  20. A

    Derive Multivariable Taylor Series

    Hello all, I am currently studying multivariable calculus, and I am interested in the Taylor series for two variable function. I am not sure where to begin; I cannot understand any of the proofs (which are apparently sparse) on the internet; they all just state it using a sigma sum; not...
  21. R

    Derive the density relation to thermal expansion

    Homework Statement Show that it follows from \frac{dV}{V} = \beta dT that, for small changes, density has a similar linear relationship to thermal expansion, namely \frac{d\rho }{\rho } = - \beta dTHomework Equations The Attempt at a Solution Well, at first glance this one seems ridiculously...
  22. K

    How do you derive E2= (pc)2 + (mc2)2

    I know you need to use some spacetime geometry to solve some conservation equations but what is the simplest way you derive the following equation about energy and momentum: E2 = (pc)2 + (mc2)2
  23. C

    Definition of Curl. Can anyone derive the gradient operator?

    "Definition" of Curl. Can anyone derive the gradient operator? Can anyone prove why this equality is true? http://en.wikipedia.org/wiki/Curl_%28mathematics%29#Definition Wikipedia says it is defined, however that's BS since the gradient operator was already defined so this needs to be proven...
  24. W

    What is the maximum number of mines in a Minesweeper board?

    I'm programming a minesweeper game, and I'm trying to come up with an equation to determine the maximum number of mines a board can have dependent on the amount of rows and columns given. I pulled some numbers from the Windows 7 version, but I'm not sure how to derive an equation from them...
  25. G

    Deriving Fractions: Simplification Rules Explained

    Does anyone know how to derive a fraction? I want to be able to differentiate f(x)=\frac{x(20-x)}{36} Ill show you what I've done but think I've just simplified it. f(x)=\frac{x(20-x)}{36} f(x)=\frac{(20-x-x)}{36} f(x)=\frac{(10-x)}{18} Is this correct?...although not sure what...
  26. C

    How Do You Derive Equations from Diagrams?

    When deriving equations, do you look at the diagrams and derive the equations from there. Could you please tell me how you would derive the equations?
  27. M

    Derive a final formula from two other formulas

    Using these two formulas derive the third formula: D/l = (D+f)/(l+alpha) D/r = (D+f)/(r+beta) D=(fb)/(alpha+beta) where D is the distance of the point from the line between the viewer's eyes; f is the focal length of the lens in the eye; b is the distance between the two eyes; and...
  28. O

    Derive Stefan-Boltzmann Law from Planck Distribution for blackbody radiation

    Homework Statement Starting with the Planck distribution R(\lambda,T) for blackbody radiation. (a) Derive the blackbody Stefan-Boltzmann law (ie total flux is proportional to T4) by integrating the above expression over all wavelengths. Thus show that R(T) =...
  29. L

    Derive a 2 order ODE from a physical problem

    Homework Statement The motion of various shaped objects that bob in a pool of water can be modeled by a second order differential equation derived from F = ma. The forces acting on the object are: 1)force due to gravity, 2)a frictional force by water, 3)and a buoyant force based on...
  30. B

    Derive a flow rate equation that accounts for the fluid properties?

    :smile:Hi I have been wrestling with this situation for a while, trying to derive an equation for it...A sphere is placed in a fluid of viscosity n and density p, outside any gravity. The sphere is instantly beamed out (perhaps by Capt Kirk?). At what volume rate will the fluid rush into the...
  31. K

    Possible to derive Lat and Lon or Cartesian X,Y,Z from Azimuth and Elevation?

    Homework Statement Is there a univeral conversion formulae to convert Azimuth and Elevation to Lat Lon or Cartesian X,Y,Z? Homework Equations So far, I have only been able to source out and successfully convert Cartesian X,Y,Z to Lat Long Alt. The Attempt at a Solution No findings...
  32. G

    Which algebra vectors satisfy this (Trying to derive Schrödinger)

    Hi, I was wondering why the wave-function in quantum mechanics is complex. There are a lot of threads in the physics section and I've downloaded a lot of papers, but they seem quite technical. So I'd like to examine the following idea (sorry if I use sloppy terms ;) ): I have an orthonormal...
  33. S

    To derive a linearized form of following equations

    hello suppose a eqn is given as y=x/(ax+b). which we can linearize as: (1/y)=a+b/x and therefore Y=A+BX where A=a, B=b and X=1/x .Another example is y=ax^b this can be written as ln y=ln ax^b or ln y=ln a+bln x therefore Y=A+bX where Y=ln y,A=ln a and X=ln x thus it is linearized now. I...
  34. D

    HELP Derive Newton's Law of cooling

    Hey guys was hoping someone could give me a hint for the derivation of Newton's Law of cooling stated in the following equation form:http://img263.imageshack.us/img263/3143/a6e5a27835e9e5738016606.png http://img716.imageshack.us/img716/8728/75784887.jpg Thanks in advance!
  35. F

    How to derive Intensity of light waves function I/Io

    Homework Statement How do you derive the following equation given I/Io= (I/N2)[(sinNØ/2)/(sinØ/2)]2 given that Ø= (2πdsinΘ)/λ Homework Equations Ø= (2πdsinΘ)/λ d=λ/sinΘ The Attempt at a Solution I have tried substituting Ø into the equation as well as d=λ/sinΘ, but I...
  36. P

    How to derive Eq. (3.110) in Peskin's book?

    Hello, I'm having trouble to derive Eq. (3.110) in Peskin's QFT book. In the book, it's said to use u(\Lambda^{-1} \tilde{p})=\Lambda^{-1}_{1/2} u(\tilde{p}) But I ran into trouble to derive this. Here is my try: The equation is equivalent to u(p)=\Lambda^{-1}_{1/2} u(\Lambda p) To...
  37. M

    Please derive equation 2.27 in Goldstein(3rd ed.)

    Please derive equation 2.27 in Goldstein(3rd ed.)
  38. S

    Derive Electric Potential Energy

    [b]1. The problem statement, all variables and given/known For a a uniformly charged sphere of radius R with total charge Q, show that the potential energy of a point charge q' varies with r U(r) = Qq'/4\pi\epsilonR * (3/2 - r2/2R2 if r < R Homework Equations \DeltaU = - \intE(r)q'dr...
  39. D

    Derive Acoustic Pressure Relation from Ideal Gass Law

    Homework Statement Derive p(r) = \frac{A}{r}e^{j(\omega t - kr)} from pV = nRT Homework Equations The Attempt at a Solution From ideal gas law I have p(r) = \frac{nRT}{V} R and T are constant, so I can pull them out now and replace them with A. If V is the volume of a spherical shell of...
  40. N

    Ball into cup off ramp, need to derive equation

    Homework Statement The problem is to find at what distance the ball has to be placed at on a ramp given a certain angle measurement of said ramp. The cup's position will be given a few minutes prior to testing so there are more unknown variables. Table Height: .73M Cup Height: 10cm Angle...
  41. I

    Derive Logic Equation from Karnaugh Map of RS Flip Flop

    Homework Statement I have attached a jpeg image of a karnough map of a rs flip flop. How can i derive the logic equation? Homework Equations The Attempt at a Solution
  42. Q

    Derive velocity function for pendulum

    Homework Statement A regular pendulum is swinging back and forth. Assuming it starts from a horizontal position, find an expression for its tangential velocity. (I don't know if the question is posed right, I just asked myself it as a challenge) 2. The attempt at a solution using a freebody...
  43. J

    How Do You Derive the Tsiolkovsky Rocket Equation?

    Homework Statement The mass of a rocket, including a full chamber of fuel, is M. Its net mass without fuel is m. The products of combustion are ejected with velocity c. If the rocket starts from rest, derive Ciolkovski's formula. Homework Equations N/A. This is actually from differential...
  44. M

    Trying to derive a transformation Matrix from a set of known points

    Hi, I don't know if this should go in a Math forum or a Programming forums, but y'all here seem quite handy with mathematics, so I'll give it a shot. If this is totally not what y'all are about, just let me know. I have two computer images... one of them is an "original" image. The other one...
  45. F

    Vertical stick falls, rotates about CM, derive v(y,theta)

    Homework Statement A uniform stick of mass m and length L, initially upright on a frictionless horizontal surface, starts falling. The circle at the center of the stick marks the center of mass. Derive an expression for the speed of the center of mass as a function of y and θ if the stick falls...
  46. S

    Derive the Period of an Oscillating Sphere

    Homework Statement Derive the period of a sphere oscillating in a hemispherical concave surface at small angles. Homework Equations Net Torque = I x alpha Delta E_m = 0 The Attempt at a Solution The thing is, tried using the conservation of mechanical energy to get an expression...
  47. H

    Need help with fourier transformation to derive oseen tensor.

    Homework Statement Derive the Oseen tensor from the Navier-Stokes equation, Consider an incompressible fluid where the velocity field \vec{v}(\vec{r},t) is given by \nabla.\vec{v}=0 (1) Assume inertia forces are negligible. Homework Equations The Navier-Stokes eq becomes...
  48. K

    A mass is attached to two strings, derive a formulas for sum of forces

    Homework Statement Two wires are tied to the 300 g sphere shown in figure. The sphere revolves in a horizontal circle at a constant speed of 6.50 m/s. What is the tension in the upper wire?What is the tension in the lower wire? Write an equation for the sum of the forces along y. Use it to...
  49. X

    Help trying to derive transfer function

    Homework Statement I am trying to derive the transfer function for the circuit (figure 6). I have what the final transfer function is supposed to be (figure 7) but I can't derive it. Homework Equations ((v2+) - 12)/12k + (v2+)/12k + ((v2+) - v1)/c2= 0 (v2-)/c1 + ((v2-) - Vout)/15k =...
  50. A

    Derive the expression for the electric field

    Homework Statement A very long, solid cylinder with radius R has positive charge uniformly distributed throughout it, with charge per unit volume \rho Derive the expression for the electric field inside the volume at a distance r from the axis of the cylinder in terms of the charge...
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