deriving Definition and 1000 Threads

  1. F

    Help Deriving Fresnel's Equations Please

    I'm trying to derive/simplify Fresnel's equation for r perp from its form: [ni cos \thetai - nt cos\theta t] / [ni cos \theta i + ntcos\thetat] to ---> - sin (\thetai - \thetat) / sin (\thetai + \thetat) From what I've gathered you need to use Snell's law ntsin\thetat = nisin\thetai and...
  2. Z

    Deriving Formula for Radius of Conical Section at Height h

    Homework Statement Suppose there is a Conical section (of a right circular cone) of total height 'l' and radii 'a' and 'b' (a>b). How do we derive the formula for the radius at a height 'h' (h<l) ?Homework Equations The Attempt at a Solution
  3. C

    Deriving an equation vs memorizing a formula

    Hi, I'm having a bit of trouble in my second semester of physics. We're covering magnetism right now. I can understand a derivation put before me of, for example, the torque due a current passing through a wire loop. However, I could never recreate this or reach a similar conclusion on my own. I...
  4. N

    Deriving Max. Velocity for Banked Curve with Friction (Centripetal Acceleration)

    Homework Statement A circular curve of radius R in a new highway is designed so that a car traveling at speed v0 can negotiate the turn safely on glare ice (zero friction). If a car travels too slowly, then it will slip toward the center of the circle. If it travels too fast, then it will slip...
  5. L

    Deriving Vr and V(sub-theta) from Kepler's second law and

    Deriving Vr and V(sub-theta) from Kepler's second law and... Homework Statement Beginning with r=[a(1-e2)]/(1+e*cos \theta) and Kepler's second law, derive general expressions for vr and v\theta for a mass m1 in an elliptical orbit about a second mass m2. The final answers should be...
  6. C

    E field phase matching at interface, deriving Snell's Law

    I'm studying optics on my own and have gotten very stuck on page 75 of Klein and Furtak, the unnumbered equation. Specifically, I don't understand why there aren't arbitrary phase factors inserted; the equation does not look general enough. I checked in Jackson, 2nd edition Classical...
  7. W

    Deriving taylor series for v/c and gamma

    Homework Statement The velocity of a proton relative to our galaxy is vp/c = 1-(0.5*10^20), i.e. almost one. Such protons are actually observed. When velocity it very nearly one \gamma is very large. 1/\gamma is very small. Use Taylor series to show that for v almost one we have...
  8. Z

    Why Must ΔS Equal Zero in Lagrange's Equation Derivation?

    I am having a problem with deriving Lagrange's Equations. It's the derivation starting from Hamilton's Principle, the part where you consider the deviation from the path: Suppose q=q(t) is the function for which the action is a minimum, and now consider a deviation from q where we replace...
  9. A

    Deriving v and a from a x(t)-function

    Homework Statement Hi again folks! I just need confirmation on this, since I'm quite sure I've got it right. Anyway here it goes. The position of a particle is given by the function x(t)= A + Bt + Ct² + Dt³. The values of the constants are the following: A= 4,0; B=2,0; C= -3 and D=1,0. a)...
  10. U

    Deriving acceleration from a position function

    Homework Statement A particle moves along the y-axis according to y(t)=(3.5 m/s2)t2 - (9.0 m/s)t + 5.0 m. (a) What is the particle's velocity as a function of time? (b) What is the particle's acceleration at t=2.0 s? The Attempt at a Solution I was wondering about b- I derived: dy/dt...
  11. U

    Deriving acceleration from velocity

    Homework Statement An asteroid moves toward the sun along a straight line with a velocity given by v = -(c1+c2/x)½ , where x is the distance from the center of the sun. Use the chain rule for derivatives to show that the asteroid's acceleration is a = -c2 /2x2. The Attempt at a Solution...
  12. S

    Deriving the De Broglie Wavelength

    E=mc^2 and E=hf. In Special Relativity, how can y=h/p be derived from E=hf?
  13. P

    How Is the Tan Power Series Derived Using Sin, Cos, and Bernoulli Numbers?

    How can the tan power series be derived from the sin and cos power series? Where do the Bernoulli numbers come in?
  14. V

    Deriving equation for ideal fluid flow problem (~bernoulli equation)

    Could anyone offer some feedback? I'm reasonably sure I got the gist of it, but I'm not sure how neat a solution it is (i.e. nothing relevant missing, or irrelevancies included). It's a past paper question so I haven't tried to tidy it up. Homework Statement Homework Equations...
  15. M

    Resolving the Paradox in Deriving Gravitational Potential Energy Function

    I'll first derive here the gravitational pot. energy by my method, and then I'll give the method that has been formally used in books. My answer differs from the actual one by a minus sign. My derivation: Let mass M be at the origin O. Let another mass m be at an arbitrary position r from...
  16. C

    Deriving Descriptions of Conic Sections from Fundamental Definition

    Everyone knows by now that a conic section is the figure formed when a plane intersects a right circular cone. Most everyone also knows that there are many different ways to describe a conic, geometrically and algebraically. What one seldom sees is the derivation of those descriptions from the...
  17. M

    Deriving the equations of torque and ang. Momentum from Newton's laws

    I know what the definition of torque and angular momentum is. But I read in a few books that "Torque and angular momentum are not independent laws of nature, and have been derived from the more fundamental laws of Newton." The above simply means, that the rotational motion is just a...
  18. T

    Deriving an expression using Bernoullis equation.

    Hi! This is my first post, so i apologise if i leave out any information. I need to derive an expression for the theoretical velocity of flow in an open channel using the Bernoulli Equation. I realize it is probably a simple question but i am sort of a beginner. Any help appreciated...
  19. M

    Deriving points conforming to bell curve

    I am writing a system that collects values from our devices (CRAH, Generators, etc) compute the trend of the data, and determine if an alarm should be raised. For testing I have a point generator and I want it to follow fairly realistic norms. Currently I generate a new point as: p.Y = p'.Y...
  20. H

    Deriving mean free path of ideal gas

    Homework Statement The mean free path for an ideal collisional gas can be calculated as shown on thishttp://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/menfre.html" . I understand the derivation, except for one thing. Homework Equations The Attempt at a Solution The molecule is...
  21. Saladsamurai

    Deriving the binomial distribution formula

    I am trying to follow along with this derivation of the binomial distribution formula: b(x;n,p) = nCx*pxqn-x But I do not really understand the meaning of the part on bold. What is this "specified order" business now? I feel like I am missing something big here.
  22. B

    How to Derive Spectral Intensity for a Laser Pulse?

    Homework Statement Electric field for a single pulse of a laser (operating at central wavelength of 800nm): E = E0e^(-(t^2/2a^2))e^(iwt) (the a is sigma and w is omega) Derive an expression for the spectral intensity (irradiance) The Attempt at a Solution One way I know to...
  23. Philosophaie

    Working with Keplerian Elements & Deriving Vernal Equinox

    I am working with the Keplerian Elements from the JPL web site. a - Semi-Major Axis e - Eccentricity I - Incilination L - Mean Longitude long.peri. - Longitude of the Periapsis long.node.or N - Longitude of the Ascending Node http://ssd.jpl.nasa.gov/txt/p_elem_t2.txt From this...
  24. mnb96

    Deriving the atan2 Function from Tangent Half-Angle Formulas

    Hello, it is mentioned http://en.wikipedia.org/wiki/Atan2#Definition" that using the tangent half-angle formulas it is possible to express the function atan2 as: \mathrm{atan2}(y,x)=2\mathrm{arctan}\frac{y}{\sqrt{x^2+y^2}+x} How can I derive this result?
  25. M

    Deriving Biot Savart's law from Ampere's law

    Can anyone help me with this? My textbook (Young and Freedman's University Physics) says that Ampere's law can be extrapolated to give Biot Savart's law but I'm not sure how to go about it.
  26. B

    Deriving dy/dx of y=logε((1+√x)(/1-√x))

    Homework Statement if y=logε((1 + √x)(/1- √x )) , show than dy/dx = (1/(√x(1-x)) The Attempt at a Solution y=logε((1 + √x)(/1- √x )) y=logε(1+√x)-logε(1-√x) dy/dx = 1-1/(1+√x) + 1/(1-√x) i don't no what to do after this or if I am even going in the right direction!?
  27. M

    How Do You Derive the Velocity Equation for the Pitt Fall Ride at Kennywood?

    Homework Statement The Pitt Fall is thrill ride at Kennywood that lifts passengers to a certain height, pauses for a few moments, and then drops the riders, causing them to free fall towards the ground before gradually applying breaks 79 ft above the ground. Assume there is a drag force, F=-bv...
  28. J

    Deriving some Laplace transforms

    Homework Statement Find the Laplace transform of each of the following functions: ... 2. f(t)=eatcos(bt) 3. f(t)=tn, were n is a positive integer Homework Equations As you well know, taking the Laplace of f(t) means ∫f(t)e-stdt from 0 to ∞ The Attempt at a Solution...
  29. P

    Deriving of the differential d(1/2v^2)/dx

    Hi, I was wondering if someone could show me how this was derived from dv/dt? I was trying to look in my notes but I think I may have copied something down wrong. This isn't a homework question but I just like to know how it works. Thank you. d(1/2v2)/dx
  30. B

    Deriving Thrust from Newton II for Rocket Motors

    Homework Statement Derive from Newton II the thrust (the force produced by the rocket exhaust) achieved by a rocket motor which ejects material with constant velocity u and mass ejection rate a. Homework Equations The Attempt at a Solution Not sure...I know how to derive vf =...
  31. L

    Deriving Lagrange's Trig Identity: Real Part of Complex # in Exp Form

    Homework Statement I did the question with help, but did not understand why did we multiply e^-i(x/2) How do I know what to multiply for getting the real part of a complex number in exponential form? Homework Equations The Attempt at a Solution
  32. Shackleford

    Deriving gradient in spherical coordinates

    I looked at my notes, but they're either incomplete or I simply forgot what the professor did to derive the gradient in spherical coordinates. Once I know that, deriving the divergence and curl given the supplementary equations listed is fairly straightforward. It was a little easier but...
  33. J

    Deriving Gauss' Variational Equation for True Anomaly

    Homework Statement Derive the Gauss Variational differential equation for the true anomaly, f, with respect to time using components along the radius, angular velocity, and a unit vector orthogonal to those two (ir,itheta,ih). Homework Equations Sorry, I don't know how to use Latex. But...
  34. L

    Deriving Newton's Law of Gravitation

    Given Kepler's Laws how do you derive Newton's Law of Gravitation?
  35. J

    Deriving Rutherford's Formula: Integrating to Find the Angle of Deflection

    Homework Statement Homework Equations This is in my mechanics book. It gives the final formula, only saying "carrying out the elementary integration..." Derive Rutherford's Formula: \phi_0=cos^{-1}\frac{a}{\sqrt{1+a^2}} where a=\frac{\alpha}{mv_\infty^2 \rho} From the equation...
  36. P

    Deriving Ernst's Equation for Complex Metrics

    I look for derivation of Ernst equation - an equation for complex function which is equivalent to Einstein equation in case of metric with two commuting killing vectors. I know this equation but I wonder how it may be derived. I also heard that teher is a simple procedure which allow to...
  37. L

    Deriving Joint Distribution Function from Joint Density (check my working pls)

    Homework Statement Given: f(x,y) = x + y, for 0<x<1 and 0<y<1 f(x,y) = 0, otherwise Derive the joint distribution function of X and Y. Homework Equations N.A. The Attempt at a Solution Using the definition, I obtained part of the joint distribution F(x,y) = (1/2)(xy)(x+y)...
  38. M

    Undetermined coefficients - deriving formula

    Homework Statement Derive a formula of the form \int\stackrel{b}{a}f(x)dx \approx c_{0}f(a)+c_{1}f(b)+c_{2}f'(a)+c_{3}f'(b) that is exact for polynomials of the highest degree possible. Apply a change of variable: y=x-a Homework Equations The Attempt at a Solution I don't get the "highest...
  39. H

    Deriving the Schwarzschild metric just by using the equivalence principle

    I've read a few papers about derivation of the Schwarzschild metric by using the equivalence principle ( http://cdsweb.cern.ch/record/1000100/files/0611104.pdf" )... but I couldn't understand them completely they assume , According to Einstein’s equivalence principle, that the influence of...
  40. P

    Stuck on math in deriving an optics equation

    Homework Statement Hi. For a project I have to derive this formula for bright fringes in optics, but I'm stuck on this simple math part (or maybe its not so simple)...ive attached a picture of where i don't understand...it might be considered a simple math problem so I'm sorry if this is too...
  41. M

    Problem Deriving Volume of a Cylindrical shell

    I have seen the derivation for the formula: h2(pi)rdr used in math textbooks. However, earlier today I had a physics problem where I needed to use the volume of a cylindrical shell of inner radius r and outer radius dr+r and length h. without remembering the formula I tried to derive it...
  42. T

    Deriving centroid of quarter circle.

    Homework Statement Find the centroid of the region cut from the first quadrant by the circle x^2+y^2=a^2Homework Equations I know that y' = (I y dA)/(I dA)The Attempt at a Solution Taking a strip dy with length x, I obtain dA = dy.x dy(a^2-y^2)^(1/2) So I y DA = I y*(a^2-y^2)^(1/2) dy from...
  43. A

    Absorbing Material Over a Slit in Deriving Double Slit Fraunhofer Interfernce Pattern

    In class we have been deriving the Fraunhofer interference pattern for a double slit experiment. I now have a question of having to derive it if one of the slits is covered with an absorbing material. I have got the equation out but I am missing a constant K... Homework Statement We have two...
  44. Q

    Deriving the needed wavefunction transformation for gauge symmetry?

    Homework Statement Take the Schrodinger equation for a point particle in a field: i\hbar \frac{\partial \Psi}{\partial t} = \frac{1}{2m}(-i\hbar\nabla - q\vec{A})^2\Psi + q\phi\Psi I'm supposed to determine what the transformation for Psi is that corresponds to the gauge transformation...
  45. S

    Deriving and Proving the Heat Equation's Integral Product

    Consider a heat equation for the temperature u of a rod of length 1: ut = uxx, 0 < x < 1, t > 0 with boundary conditions ux(0,t) = 0 & u(1,t) = 0. I derived Xn(x) = cos((n+1/2)\pix) using separation of variables. How do I show that \int_{0}^1 Xn(x)Xm(x) dx = 1/2 if m = n and 0 if m...
  46. M

    Equation Editor: Deriving Exp[m1t-m2t-m3t] with Word

    exp[m1t-m2t-m3t] mew-number bottom right-t Since t is common to each, there must be a better way of writing that. I am using equation editor with word, which doesn't paste here. Any help gratefully received.
  47. M

    Deriving EOM to Describe Wheelie Motion of a Car

    Homework Statement Equations of motion are to be derived to describe the motion of a car(rear wheel drive) at rest which then accelerates to perform a wheelie. Basically, I need equations of motion that would help me determine the force that the rear wheels exert on the car in order to...
  48. N

    Deriving the displacement equation for a sinusoidal wave

    Hi everyone, I'm trying to understand the derivation of D(x,t) = A \sin{(kx - \omega t + \phi_o)} which is the displacement equation for a sinusoidal wave. The way my textbook (Physics for scientists and engineers by Knight) does it: Look at the graph of displacement versus position at time...
  49. Z

    Physics question about deriving a one dimensional kinematic equation?

    Okay, we all know that ΔX = ViT + 1/2AT^2 Say I drop a stone from rest and I want to find its distance at a given time knowing the acceleration. Since the initial velocity is zero and its accelerating vertically we can say. ΔY = 1/2AT^2 ΔY = (AT^2) / 2 <------------------------- Keep in mind...
  50. S

    Deriving angular velocity vector algebra?

    where x represents cross product currently if i forget i figure these out using the right hand rule, but how do you get each equation visa versa using vector algebra i started with w = rxv how do you derive that v = wxr i got up to this w = rxv w= -(vxr) rxw = -rx(vxr) rxw =...
Back
Top