What is deriving: Definition and 1000 Discussions

SI derived units are units of measurement derived from the
seven base units specified by the International System of Units (SI). They can be expressed as a product (or ratio) of one or more of the base units, possibly scaled by an appropriate power of exponentiation (see: Buckingham π theorem). Some are dimensionless, as when the units cancel out in ratios of like quantities.
The SI has special names for 22 of these derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m2), the SI derived unit of area; and the kilogram per cubic metre (kg/m3 or kg⋅m−3), the SI derived unit of density.
The names of SI derived units, when written in full, are always in lowercase. However, the symbols for units named after persons are written with an uppercase initial letter. For example, the symbol for hertz is "Hz", while the symbol for metre is "m".

View More On Wikipedia.org
Recent contents Top users
  1. W

    Deriving a formula for calculating dB based on distance

    Homework Statement Decibel level from source at 1.0 m is 60.0 dB Find dB level at distance 2.0 m. Homework Equations dB = 10 log10 (I/I0) <- this one I know but couldn't see an application. Forgot to add that I0 is equal to 1.0 x 10^-12 W/m^2 dB = dBi - 20 log10 (r2/r1)...
  2. L

    Help deriving expression of current density

    Hey I got an assignment where I have to get an expression of the current density to be: j = -e\int \frac{dk}{4\pi ^{3}} v_{x}f(k) It says k_{x} >0 underneath the intergrale. The current is flowing to the right (velocity of v_{x} > 0) Where f(k) is the fermi-dirac distribution function...
  3. S

    Deriving the standard deviation of a resultant vector

    I am working with some wind speed data and need to work out the standard deviation of the magnitude of the horizontal wind. Unfortunately the only information I have is the standard deviation for the streamwise and cross-stream components of the wind (which are orthogonal). Is it possible to...
  4. jfy4

    Deriving EFE from the Bianchi Identities

    Hi, I ran this by my friend awhile ago and I'm not sure how to feel about it still... Consider the following: We know \nabla_\alpha G^{\alpha\beta}=0\implies \partial_\alpha G^{\alpha\beta}+\Gamma^{\beta}_{\gamma\delta}G^{ \gamma \delta}+\Gamma^{\delta}_{\delta\gamma}G^{ \gamma...
  5. J

    Deriving the Schwarzschild Metric

    I've worked through a common-sense argumenthttp://www.mathpages.com/rr/s8-09/8-09.htm" showing the time-time component of the Schwarzschild metric g_{tt} = \left (\frac{\partial \tau}{\partial r} \right )^2\approx 1-\frac{2 G M}{r c^2} On the other hand, I've not worked through any...
  6. L

    How do I derive a wave function for an electron in a finite potential well?

    I'd like to get some help and pointers on how to derive a wave function. Since I'm not really good at physics I'm just going to use brute force, if anyone spot a mistake please please point it out. If I look at an electron in an well with infinite potential walls. The well has the dimensions...
  7. bcrowell

    Deriving GR from maximum power

    MTW has a cute argument on p. 980 that the maximum power radiated from any system is a fixed number, about 10^53 W. I came across this and filed it away as a piece of cool trivia. But it turns out that apparently you can derive the GR field equations from nothing more than the assumption that...
  8. R

    Deriving expressions for creation/annihilation operator

    hey guys!I really need help in getting from the real classical solution of the Klein Gordon equation to the expression of operators! I start from: \varphi(x) = \int \frac{d^3 k}{(2\pi)^3 2\omega} [a(\textbf{k}) e^{ikx} + a^{*}(\textbf{k}) e^{-ikx}] and should arrive with \int d^3 x \...
  9. M

    Deriving thermodynamic relations

    1. The problem statement: Show that a) (∂H/∂T)V = CV(1 - βμ/κ) b) (∂H/∂V)T = μCP/Vκ c) (∂T/∂V)H = μ/(V(μβ - κ))2. Homework Equations : i) β = (1/V)(∂V/∂T)P ii) κ = -(1/V)(∂V/∂P)T iii) β/κ = (∂P/∂T)V iv) CV = (∂U/∂T)V v) CP = (∂H/∂T)P vi) CP - CV = TVβ2/κ vii) η = (∂T/∂V)U = (1/CV)(P -...
  10. M

    Deriving the Phonon Dispersion Relation using Quantum-mechanical approach

    I'm doing a literature review on dispersion relations, and I've been told that if i can derive the phonon dispersion relation, it would help my review. So i was wondering if anybody could help me with the derivation either through Quantum-mechanical approach or Semi-classical treatment of...
  11. R

    [Linear Algebra]- Simultaneous equation. Deriving the general solution.

    Hello, I need help with solving the following simultaneous equation. I tried using matrix solution using Gaussian elimination but it became too difficult early on. Known constants are a,A,b, and B. Known variables are x and y. Unknown variables are m and n. (a\timesx)/(A - x) +...
  12. H

    Deriving Apoapsis and periapsis formulas

    Hello, I'm wondering if anyone can tell me where these formulas for RA and RP (apoapsis and periapsis) come from. RA = \frac{a(1-e^{2})}{(1-e^{2}sin^{2}(LatB))^{3/2}} RP = \frac{a}{(1-e^{2}sin^{2}(LatB))^{1/2}} If you multiply RA by \frac{1-e^{2}sin^{2}(LatB)}{1-e^{2}}, you can get RP...
  13. L

    Deriving Moseley's Law Using QM/QFT

    Like Bohr had derived Rydberg's formula for hydrogen emission spectra, has QM/QFT been able to derive Moseley's law which gives emission spectra for multi-electron atoms.
  14. T

    Solving the Mystery of Deriving O2 Concentration in H2/O2 Mixture

    In a spherical vessel with a hydrogen H2 and oxygen mixture O2 it is stated in a problem that we can derive that the concentration of oxygen [O2] can be derived to be: P / 3RT. With P the total pressure, R the gas constant en T temperature? How on Earth is this possible? I thought the...
  15. R

    Deriving the Claim: \sin^2\theta/r Conservation in Pulsar Gamma-Ray Emission

    When I study the mechanism of gamma-ray emission from pulsars, I got a statement saying that the quantity \sin^2\theta/r is conserved along any dipolar magnetic field line. Does anybody know how to derive this claim? Thanks in advance.
  16. H

    Projectile Motion- deriving formulas

    Homework Statement I need to know how the equation Dx= Vx\sqrt{}2(Dy)/a is valid.
  17. L

    Deriving an expression for internal energy.

    Homework Statement Show that the change in internal energy of a simple system between states (V1, T1) and (V2, T2) is given by ∆U = \int^{T1}_{T2} C_v\ dT + \int^{V1}_{V2} T.\frac{\partial p}{\partial T}|_V - p \ dVHomework Equations dU=dQ-pdVThe Attempt at a Solution As U is a function of...
  18. M

    Attempt at Deriving the Volume of a Cone

    Hi, so this morning I made an attempt at this... With javascript (website programming language) I was able to successfully yield the ratio of the volume of a cone compared with the volume of a cylinder (1/3). This is the source code: And basically this is the idea. It's a summation of the...
  19. A

    Deriving an equation for the electric field at a point charge

    Homework Statement Use V=kq/r, E(x) = V/x, E(y) = V/y, E(z) = V/z to derive an expression for the electric field at a point charge q. E(r) = ? Homework Equations E= F/Q
  20. A

    Deriving an equation for the electric field at a point charge

    Homework Statement Use V=kq/r, E(x) = V/x, E(y) = V/y, E(z) = V/z to derive an expression for the electric field at a point charge q. E(r) = ? Homework Equations E = F/Q
  21. P

    Desperate Deriving Ideal Gas Formula

    I know how temperature, volume and pressure are related and I think (think because I haven't tried any exercise alone yet) I can apply PV = nRT with no problems. But usually I am not able to apply a formula until I understand how I got to it, what it means. I'd like to start from the beginning...
  22. A

    Deriving info from reducible representations

    Heres the reducible representation made by counting the number of bonds left unchanged by each symmetry operation of water: http://img808.imageshack.us/img808/704/red0.png and here's the irreducible representations extracted from it: http://imageshack.us/m/695/3829/red01l.png in the book...
  23. L

    Deriving the damped circuit equation and energy dissipated through a resistor.

    Homework Statement I figure I will just combine these two questions into one topic. 1) The energy stored in a capacitor is .5CE^2, where E is the voltage. Wat is the instantaneous power dissipated in a resistor R through which this capacitor discharges? Show that the total energy dissipated...
  24. E

    Help with deriving this diffraction equation

    Homework Statement Hi! I need help with showing how to derive this formula for the diffraction of a laser: m λ = d (sin(θm) - sin(θi)) where: d = groove spacing m = order of diffraction λ = wavelength of laser θi = angle of incidence θm = angle of diffraction Homework Equations I found this...
  25. S

    Deriving expression for capacitor voltage

    Homework Statement For the following circuit, obtain an expression for the capacitor voltage, vC(t), for time, t (greater than or equal to) 0 if vs(t) = 10 V and vC(0) = 2 V. Homework Equations KVL Definite integrals, differentiation etc The Attempt at a Solution Right so I...
  26. G

    Deriving arcsin(1-2e^-t): What Chain Rule to Use?

    1. Derive arcsin(1 - 2 e ^-t) 2. The derivative of arcsin is 1/√(1-x^2) 3. I tried using the chain rule for 1 - 2 e ^-t, but that didn't work out. What should I take the chain rule of?
  27. E

    Deriving the first moment of area of semicircle

    Homework Statement Derive via integration the first moment of area Q of a semicircle with radius r. Homework Equations Q = \int_{A} y dA A_{semicircle} = \frac{\pi r^{2} }{2} The Attempt at a Solution A = \frac{\pi r^{2} }{2} A(y) = \frac{\pi y^{2} }{2} dA = \pi y dy Q =...
  28. C

    Why is the Speed of Light Constant in Time Dilation?

    So when we derive time dilation, and when we have a train moving and we shoot a light beam from the bottom to the top, to an outside observer not on the train he will see the light leave at an angle. So my question is why don't we factor the horizontal speed of the train in order have the...
  29. D

    Deriving Length Contraction From Lorentz Transform

    Homework Statement From Lorentz Transform, x^{\prime} = \gamma (x - vt) From textbooks and wikipedia, L_0 = x'_2 - x'_1 = \gamma (x_2 - x_1 ) Where x_1 and x_2 = L Thus, \L_0 = \gamma L Question is this: If i take the same method and us the Inverse Lorentz transform, i seem to...
  30. B

    Error Analysis- Deriving Equations

    Homework Statement In this experiment, the acceleration due to gravity is related to the time, t, it takes the ball to fall to a distance , y, by Eq. (3). With this equation and Eq. (2), show that the fractional error, ∆g/g is ( (∆y/y)^2 + (2∆t/t)^2 ) ^1/2 Homework Equations Eq. (3) =...
  31. F

    Deriving the speed of light from the Pythagorean Theorem

    Has anyone heard of the speed of light being derived from the Pythagorean Theorem? Obviously I'm referring to using the time dilation effect of motion. Frank
  32. P

    Deriving the Geodesic formulae

    [b]1. A straight line in flat space may be defined by the equation: (when I use the ^ symbol in this case it means like upper subscript not to the power) (U^v)(d/dx^v)(U^u)=0 (U^u=dx^u/ds) derive the geodesic equation. Please help I'm completely clueless all I can really see to do...
  33. E

    Deriving Energy and Wave Functions from 3D Schrödinger

    Homework Statement I have a quantum harmonic oscillator with quantum numbers nx,ny,nz ≥ 0 and frequency ω0. There are three parts to the problem. To me it seems they are out of order, but I'm kind of shaky deriving these. a) Write down the energy level Enx,ny,nz of a QHO in 3d with quantum...
  34. D

    Deriving the MGF for the Weibull Distribution

    I'm attempting to derive the MGF for the Weibull distribution. I know that E(e^{tx}), which equals the integral shown here: http://www.wolframalpha.com/input/?i=Integrate%5Be^%28t*x%29*%28k%2F%CE%BB%29*%28x%2F%CE%BB%29^%28k-1%29*e^-%28x%2F%CE%BB%29^k%2Cx%5D where the parameters are k and λ...
  35. A

    Can the Surface Area of a Sphere be Derived by Integrating Circumferences?

    Homework Statement So I wanted to try and derive the surface area of a sphere with radius r. My plan was to basically integrate the circumferences of disks from 0 to r and then multiply it by 2. The Attempt at a Solution I got this: 4\pir^{2} \int^{\pi/2}_{0}cos^{2}\theta...
  36. F

    Deriving Biot-Savart's Law, kinda a math problem not really physics

    Homework Statement Basically I am deriving Biot-Savart's Law using the vector method. The one my book gives me is impossible to rememberThe Attempt at a Solution http://img39.imageshack.us/img39/6584/pictureson.th.png Uploaded with ImageShack.us So I am actually just going to do the...
  37. T

    Deriving equations involving sin and cos

    Homework Statement I'm asked to derive equation(2) from equation(1). equation(1): d=(tsin(2i))/((n^2-sin(i)^2)^1/2) equation(2): n=sin(i)(((2tcos(i/d))^2+1)^1/2) Homework Equations The Attempt at a Solution My attempts have got me nowhere, and I don't know how to even...
  38. T

    QM - Deriving the Ladder Operators' Eigenbasis

    I'm am trying to derive the relations: a|n\rangle=\sqrt{n}|n-1\rangle a^{\dagger}|n\rangle=\sqrt{n+1}|n+1\rangle using just the facts that [a,a+]=1 and N|n>=|n> where N=a^{\dagger}a (which implies \langle n|N|n\rangle=n\geq 0). This is what I've done so far: [a,a^{\dagger}]=1 \Rightarrow...
  39. D

    Deriving Coefficients for Calculating Figure of Merit

    Homework Statement Hi... Don't know if it's actually homework, since it's not, but I hope it's okay to post in here. I am looking for a paper/website/article of some sort, that might have the derivations of the above mentioned coefficients ? It's for calculating the figure of merit...
  40. K

    Deriving Moment of inertia for a hollow sphere

    Homework Statement How do you derive the moment of inertia for a hollow sphere? I am not ending up with what i need to get which is: (8pir^5)/9 Homework Equations I am not sure if the bounds are correct or if we need to factor something else in. The Attempt at a Solution A double integral...
  41. E

    Deriving Motion Equation from Newton's Second Law

    Homework Statement An object is dropped from a height above a pool of water. Start with Newton’s 2nd law, F = ma and use the general expression for acceleration, ay=d2y/dt2 to generate a differential equation Homework Equations F=ma -mg=m d2y/dt2 The Attempt at a Solution We had this...
  42. T

    Deriving equations involving sin and cos

    Homework Statement This problem deals with the displacement of a light ray as it travels through a glass medium. Starting with the equation #1: d=S[sin(i)cos(r)-cos(i)sin(r)] (where d=the length of displacement of the light ray in the glass medium, i=angle of incidence...
  43. S

    Deriving the Lorentz transformation

    Homework Statement Derive the Lorentz transformation by assuming that the transformation is linear, and does not change the perpendicular coordinates. Write the transformation as x' = A1 (x - vt), y' = y, z' = z, t' = A2 t + A3 x, Determine A1, A2, A3 by requiring that a flash of light...
  44. C

    Deriving equation of motion for Overhead Crane

    Homework Statement 1)Derive equation of motion for trolley. 2)Derive the equation of motion for the load using balance of torques. 3)Then relate the force applied to the angular displacement of the load. Coefficient of friction between trolley and rail is negligible. For the moment of...
  45. D

    Deriving 1D Wave Equation for Vibrating Guitar String

    I'm doing a project on a vibrating guitar string and I have completed all the simulation and experimental work, but I do not fully understand the theory behind it. I need to derive the 1 dimensional case of the wave equation, as the 1 dimensional case is considered to be the most convenient...
  46. J

    Deriving an Integrating Factor for a Non-Exact DE w/ Multiple Dependencies

    I was looking at how to derive an integrating factor for a non-exact DE that has multiple variable dependency, i.e. µ is xy-dependent, and I found the explanation at the link in the middle of the page at equation (22) (link...
  47. E

    Deriving Formula for Concentration of Hydronium at Equivalence Point?

    Homework Statement This is a part of the lab report for a practical I did last week. I need to derive the following formula for the concentration of hydronium at the equivilance point of a strong base weak acid titration (acetic acid with sodium hydroxide). Homework Equations M=V/c...
  48. I

    Deriving RPM for Object Slipping from Rotating Surface

    Homework Statement A object(have mass M1) is placed at a R1 distance from the center of a horizontal surface that can rotate. The surface rotation is very FAST INCREASE ( tangential acceleration is non-negligible) until the surface reaches a cirtical rotation rate. At that instant, the object...
  49. R

    Simplest way of deriving Lorentz transforms

    Is there a way to derive Lorentz transforms by knowing just Galilean/Newtonian relativity (adding up velocities) and Pythagoras theorem? I do not understand the principle of homogeneity or any higher mathematics. I can derive t' = gamma * t by using common sense and Pythagoras theorem. I am...
  50. H

    PLEASE HELP in Deriving Terminal Velocity Equation

    PLEASE HELP! in Deriving Terminal Velocity Equation :) Homework Statement The terminal velocity of a mass m, moving at 'high speeds' through a fluid of density ρ(kg m^-3), is given by v = sqrt(2mg/DρA) where A is the cross sectional area of the object (m^2) and D a dimensionless "drag...
Back
Top