What is Difference: Definition and 1000 Discussions

A finite difference is a mathematical expression of the form f (x + b) − f (x + a). If a finite difference is divided by b − a, one gets a difference quotient. The approximation of derivatives by finite differences plays a central role in finite difference methods for the numerical solution of differential equations, especially boundary value problems.
Certain recurrence relations can be written as difference equations by replacing iteration notation with finite differences.
Today, the term "finite difference" is often taken as synonymous with finite difference approximations of derivatives, especially in the context of numerical methods. Finite difference approximations are finite difference quotients in the terminology employed above.
Finite differences were introduced by Brook Taylor in 1715 and have also been studied as abstract self-standing mathematical objects in works by George Boole (1860), L. M. Milne-Thomson (1933), and Károly Jordan (1939). Finite differences trace their origins back to one of Jost Bürgi's algorithms (c. 1592) and work by others including Isaac Newton. The formal calculus of finite differences can be viewed as an alternative to the calculus of infinitesimals.

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  1. MattGeo

    I Reference Frame, Difference in Kinetic Energy, Fuel Consumed

    Say 2 cars are traveling side by side at 10 m/s in some flat, wide open space. Relative to each other they are stationary. Relative to someone on the ground they are both moving at 10 m/s. Now say you're in 1 of the cars and you see the other car accelerate, changing his velocity by 10 m/s in...
  2. abdulbadii

    What is the difference in cooking oil before and after frying heavily?

    What's actually details in difference of any cooking oil (vegetable, palm oil, etc) before and after exhaustive/heavy cooking ? As only heard not clear or reliable folks' says, the many unsaturated bonds turns to be saturated afterward.. The need arose as it's quite affirmed that the former is...
  3. Tertius

    A Difference Between Scalar Field Solutions in Curved Spacetime

    A general free field Lagrangian in curved spacetime (- + + +), is given by: L = -1/2 ∇cΦ ∇cΦ - V(Φ) when the derivative index is lowered, we obtain: L = -1/2 gdc∇dΦ ∇cΦ - V(Φ) then we can choose to replace V(Φ) with something like 1/2 b2 Φ2 so: L = -1/2 gdc∇dΦ ∇cΦ - 1/2 b2 Φ2 ** I will...
  4. F

    I Finite difference scheme for u'=u^2, u0=1, 0<t<2

    u'(t)=u(t)^2, u(0)=1, 0<t<2 What finite difference scheme can overcome the difficulty when t->1+ and help the solution jump to the negative branch?
  5. M

    MHB Confidence interval of difference

    Hey! :giggle: From two populations of small and medium enterprises, we collect two random and independent samples of size $n_1 = 64$ and $n_2 = 36$ enterprises respectively. If we calculate for the companies of the first sample average sales of $9$ thousand euros and a variation of $4$, while...
  6. T

    I How a Battery creates a Potential difference in an electrical current

    Hello, I'm seriously confused on several things around how concretely batteries create potential difference in order to force the electrons circulate trought the circuit wire. Almost all explanations I found (wikipedia, diverse tutorials, intro scripts, etc.) explain it in nearly the same...
  7. F

    I Conservation of finite difference for vibration equations

    Let's discuss whether the energy under a finite difference (FD) scheme is conserved. Take the simplest vibration eq mx''+kx=0, which one will use a FD scheme to solve. The energy is mx'^2/2+kx^2/2. Whether the energy is conserved doesn't depend on the FD scheme for the ODE but upon the FD scheme...
  8. redtree

    B Difference between a continuously differentiable function and a wave

    What is the difference between an absolutely continuously differentiable function and a wave? Are all absolutely continuously differentiable equations waves?
  9. E

    Finding the potential difference between 2 points in a circuit

    is this method accepted? 2V is split equally between the 2 5kohms resistor because they are of equal resistance. 2V=5kohms 2kohms= 0.8V 3kohms=1.2V. p.d across P and Q= 1V-0.8V=0.2V
  10. nuckshuck11

    B Lifting an object with a mass difference of just 1kg

    Hello, can anyone help me out with this? If i want to lift an object that weights 100kg and I am going to do it with a 101kg of force (990,81 N ). Then my acceleration would be; a = F/m a= 990,81N / 101kg = 9,9081 m/s2 but gravity is pulling it down so then I am acually accelerating it with...
  11. I

    Help Plotting Phase Difference using LTSpice please

    How do i plot phase difference in a Ltspice in this circuit ?
  12. S

    Finding path difference of EM waves received by radio telecopes

    My attempt: I think ##x## is the path difference so by using trigonometry, I got ##x=d \sin \theta## But my teacher said the answer is ##d \cos \theta## What is my mistake? Thanks Edit: Sorry, I found my mistake. My ##x## is not the path difference
  13. oscarrod5

    Exploring Phase Potential Difference in 3-Phase Power

    I understand phase voltage (phase to neutral) well, but I'm still confused by what exactly the potential difference is between any 2 phases in 3 phase power. If you were to try to find the potential difference where 2 sine wave phases cross, then at that instantaneous point, the potential...
  14. Dario56

    I How is Potential Difference Created in Electrolytes?

    When we have a resistor in electronic conductors, potential difference is created via surface charges which accumulate on conductor surface. What about electrolytes? I am not sure if electrolytes can create potential difference in the same way since surface in electrolytic conductors isn't as...
  15. N

    Engineering Finding Impulse Response of Difference Equation

    And really that's all I know how to do myself. If someone can explain/lead me through this, that will be very helpful. Thanks
  16. Russ Edmonds

    I The dramatic difference between wet and dry sphere splashes

    Caution: This video has music. Turn sound off before watching if this bothers you!
  17. I

    Percent change vs. percent difference

    What is the difference between percent change and percent difference? When would you use one over the other? Thanks.
  18. S

    What is the difference in this limit?

    Hello! I need to calculate the limit of this function ## f(x) = (x^2-9)*e^{-x}## for + and - ## \infty ## Now for + infinity I did this $$ \frac{(x^2-9)}{e^x} $$ apply L'Hospital since we have infinity divided by infinity; $$\frac{2x}{e^x} $$ Apply L'Hospital again $$ \frac{2}{e^x} $$ the...
  19. A

    A The difference between the binding of molecules and superconductors

    Molecules and superconductors bind due to overlaps of the wave functions of the electrons. 1. What is the difference between these two then? 2. Why can't we look at molecules as a macroscopic wave function?
  20. Y

    Difference in destructive power between a heavy stick and a light stick?

    I am practice stick fighting for self defense. I have a question I don't know how to judge. Say if I have a 6oz and a 12oz stick both 28" long. I swing them to hit an object, assuming I have the same strength, obviously the velocity is faster with the lighter stick and slower with the heavy...
  21. C

    Calculating Magnitude Difference: Is it Right?

    I have found the difference in the magnitude from the counts to be -.073 using -2.5log(11347/10606) but I m unsure if this is right or how to calculate the uncertainty
  22. ZdMh

    About difference in Velocity and motion in Jet engines

    I was watching a video about jet engines, and it was obvious for me and for the instructor that if we compress air at high speed from the gas turbine inlet, then after multiple stages collide with the turbines blades inside, the body will move in the sense of difference in velocity, so forward...
  23. V

    BLDC Motor - Finding out how many Pairs of Poles and the difference with PMSM

    Hello Community, i have BLDC motor with General parameters are 3 Phase motor with 4 Poles, 36V, 7.3A rated current, 4000RPM rated speed. you can check datasheet on link below The first question is how many Pair of Poles does this motor have? 2 or 4? For example the motor bellow...
  24. E

    Confusion about the difference between isolated and non isolated systems

    Read the book and conducted research on the internet. Came to conclusion that this was an isolated system because the girl was being accelerated by gravity but answer is non isolated. Can someone please help me grasp this concept better.
  25. K

    Difference Between FEA Result and Hand Calculation in Beam Bending?

    This is the analytical working out. I substituted the value of 306mm ( the maximum length of the beam) to find the maximum deflection along the Z-axis. Which came out to be -2.39mm. But according to Ansys the average deflection is 0.3mm and the maximum deflection is 0.8mm. This is the Ansys Values.
  26. D.S.Beyer

    B SR vs GR - Visual Difference between Length Contraction

    The 2 Bowling Balls Ball(a) & Ball(b) (a) is in acceleration of 10m/s^2 (b) is in at fixed position in a gravitational field where g=10m/s^2 In both cases the observer is: - perpendicular to the vector of acceleration - distant enough to be in empty flat space Question : In an instantaneous...
  27. yourheartandsoul

    Finding blood pressure from density and height difference

    I did (1300)(9.81)(0.67) and got 8544.51 N/m^2 but unsure if that was the correct route to take. Please confirm or deny if I was approaching it in the correct way!
  28. J

    Find the phase difference in terms of d, lambda, theta

    So in figure 4.8 the path difference between the two waves is d*sin(theta), then is the phase difference just (d*sin(theta)*2*pi)/lambda?
  29. J

    Determine energy state difference using absorption-emission spectra

    Hello, I was wondering if someone could help clarifying this question. The question asks to estimate the energy state difference between the vibrational ground state of S0,v=0 and the first excited vibrational ground state S0,v=1 of the spectra below. The given solution: S1,v=1 -> S0,v=1 at...
  30. A

    MHB Why x2 +1 and x2 -1 are Not/Are Difference of Squares

    Explain why x2 +1 is not a difference of squares and x2 -1 is
  31. T

    POTENTIAL DIFFERENCE AND ELECTRIC FIELD HOMEWORK

    I tried following the formula but it wasn’t correct. I’m sure I could get it if I had an example as I’m sure this must be a simple question for other people I was just unsure if I was doing it correct.
  32. P

    Temperature difference by Dimensional analysis.

    Attempt at solution: I wanted to try and solve this with dimensional analysis. I reasoned that I would chose the following dependent variables: - [V] : Volume ( of the block) - [Q] : Heat ( the radioactive decay would cause some heating of the water) - [R]: Radiation - [Cv]: Heat capacity...
  33. maistral

    A Difference between MAPE and SSE

    I am working on an equation that is supposed to model two dependent variables Y and Z using four parameters a, b, c, and d (for regression) and a single independent variable X. What I am doing is that given a set of values for X, I am going to regress a, b, c, and d to fit Ycalc and Zcalc to...
  34. I

    Difference in tension introduced by friction

    I have no clue how to do this, so I did my best guess of it. Friction is μN, N being the normal force. The normal force when it is in contract with the pole should be V2/R, R being the radius of the pole. So ΔT = μV2/R The answer provided is μTΔθ
  35. H

    Potential difference between the center of a sphere and a point 4.0 cm away?

    I can use integral as attached to obtain the answer. However, I wonder why I can not use " V = KQ / r " the get the correct answer. Thanks.
  36. T

    What are the limitations of the Explicit Finite Difference Model?

    Homework Statement:: Discuss the limitation of the Explicit Finite Difference Model. Relevant Equations:: no formula Hello there, I have to discuss the limitations of using the Explicit Finite Difference model to calculate a 2D Heat Diffusion through an aluminium place, however, I really...
  37. T

    Matlab report help please (Finite Difference Method)

    We have to submit a Matlab (my worst module) assignment to show the heat transfer on a plate. However, I have the 2 codes almost done but I am struggling to write the report. To calculate the temperature on a 2D aluminum plate we need to use the Explicit Finite Difference Method. The problem...
  38. Demystifier

    A Difference Between Collapse and Projection

    [Moderator's note: Spun off from a thread in the QM forum to separate out the interpretation discussion.] Yes, but I was hoping that you could give a precise specification of the difference. (In my opinion, @vanhees71 never specified the difference precisely.)
  39. L

    A What is the difference between groups SU(n) and SO(n,C)?

    What is the difference between groups ##SU(n)## and ##SO(n,\mathbb{C})##? They look completely the same.
  40. Euan12345

    Using phase difference to find the angle of a signal

    I want to locate an infrared signal using Angle on arrival (AoA), I have elected to use Phase Interferometry to achieve this, I am however struggling to understand how the phase difference (∆ϑ) is found. Can someone explain how I could find this?
  41. F

    I What is difference between EM wave and EM field?

    They say wave function is different to quantum field. Then what is the difference between EM wave and EM field?(By the way :Is that EM wave the wave function of photons?).It seem to me EM wave is the wave of EM field?
  42. L

    A Understanding Tensor Notation: What is the Difference?

    I am struggling with tensor notation. For instance sometimes teacher uses \Lambda^{\nu}_{\hspace{0.2cm}\mu} and sometimes \Lambda^{\hspace{0.2cm}\nu}_{\mu}. Can you explain to me the difference? These spacings I can not understand. What is the difference between...
  43. S

    Potential difference across the ends of a solenoid

    Emf between the center of the disc and its rim = ##- \frac{d \phi}{dt }## = ##-B.A \frac{d \cos (\omega t)}{dt}## =##\mu_0 \frac{N}{L} I A \omega \sin (\omega t)## Potential difference across the ends of the solenoid = ##10\mu_0 \frac{N}{L} I A \omega \sin (\omega t)## Is this correct? How to...
  44. Janus

    The difference a new computer makes for 3D rendering

    Just recently, I finally upgraded my 7+ year old computer. I was able to find a good deal on a HP Omen, with a Geforce RTX 2060 graphics card. So, not only was I able to upload the latest build of Blender, but I was able to go back and tweak some renders I had done with the old computer. For...
  45. waazwag

    Induced voltage difference in a magnetic field

    Hi everyone, I'm currently working on the problem listed above. I'm pretty new to electrodynamics, and I'm learning on my own through a book. I was wondering if someone can please help me through this problem. Here are my thoughts:I think I need to use Faraday's Law of Induction for part (a)...
  46. C

    B How to prove the associative law of symmetric difference?

    I'm trying to prove the associative law of symmetric difference (AΔ(BΔc) = (AΔB)ΔC ) with other relations of sets. A naive way is to compare the truth table of two sides. However, I think the symmetric difference is not a basic one, it is constructed form other relations, that is AΔB =...
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