Match Definition and 130 Threads

A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by frictional heat generated by striking the match against a suitable surface. Wooden matches are packaged in matchboxes, and paper matches are partially cut into rows and stapled into matchbooks. The coated end of a match, known as the match "head", consists of a bead of active ingredients and binder; often colored for easier inspection. There are two main types of matches: safety matches, which can be struck only against a specially prepared surface, and strike-anywhere matches, for which any suitably frictional surface can be used.

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  1. Paul Howard A

    I Do Emission and Absorption Spectra Match? A Non-Physics Minded Tourist's Guide

    Basic stuff. Do emission and absorption spectra match? If so, why wouldn't hot stellar atmospheres exhibit both, cancelling? I'm a tourist...not physics minded..
  2. shivajikobardan

    What strings does this regex match? (a|b)*

    regepxal is showing infinite matches and shows "baaaaaaa" as a match. Doesn't (a|b) means a or b? * means match 0 or more times. So, it should be matching aa,aaa,bb,bbb, , etc? I'm not getting how baaaa is a match. Can anyone clarify please?
  3. M

    Python Does this python script match the math?

    Hi PF! I've posted a bunch lately and you have been SO helpful (seriously, thank you all). Can you corroborate if my python script below matches the math? I'd seriously appreciate it! The math: $$\max_{x\in [0.7,1)}F(x) : F(x) := \sum_{t = 250}^{750} \log\left( P_{\nu=3} \left(...
  4. chwala

    Determine the probability that Andy wins the match

    My interest is on the highlighted part only...the other questions are well understood. Find ms solution here; Even this is well understood...they made use of sum to infinity to arrive at the solution. I am interested on an alternative approach. Cheers guys.
  5. M

    MHB Calculate Data Points to Match Given Totals

    Hello! I have a super tricky problem for everyone I truly hope there is an answer to this. I have different data sets all of which are a different amount of number per set (total points per set) Each number is multiplied by 4.86 then rounded down. Then the total is added Alternatively the sum...
  6. jim mcnamara

    Bat wild virus -very close match to SARS-Cov2-19

    Paper, accepted during editing into researchsquare.com, part of nature.com. https://www.researchsquare.com/article/rs-871965/v1 Two species of bats in Laos had Corona viruses very close to the SARS-Cov2-19 virus. Closer than any other virus found. They infect human cells via ACE2, in...
  7. tworitdash

    MATLAB MATLAB IFFT doesn't match the analytical one

    I have a Gaussian shape frequency domain spectrum of which I am calculating the Inverse Fourier transform. I use both IFFT of MATLAB and also an analytical expression of Mathematica. They are not the same. I don't know where it is wrong. I have pasted both the figures. The numerical one has...
  8. V

    Does the exhaust of a truck match the velocity of the truck?

    My doubt is whether its correct to assume that the exhaust is having the velocity of truck when it comes out of the exhaust pipe. So, I am not sure if Ve = Vt. Should not the exhaust come out in a south direction from exhaust pipe since truck is moving in north direction? If yes, then it cannot...
  9. Cerenkov

    B The match rates in Bell Tests -- Lower than 50%?

    Hello. A friend and I are having a good-natured argument about tests of Bell's Theorem and he has directed me to this link. http://electron6.phys.utk.edu/phys250/modules/module 3/entangled_electrons.htm Our understanding of quantum physics should be considered as Basic. What we would like to...
  10. J

    Stainless Steel track surface grade to match a 440C roller?

    I have a machine I am designing that has a carriage supported by Track rollers on a machined flatbar track. The load that each individual roller will experience could reach 2000lbs. worst case scenario. The track surface is machined 304L - 1" wide as you can see in the green in the attached...
  11. M

    How to 'shift' Fourier series to match the initial condition of this PDE?

    Hi, Question: If we have an initial condition, valid for -L \leq x \leq L : f(x) = \frac{40x}{L} how can I utilise a know Fourier series to get to the solution without doing the integration (I know the integral isn't tricky, but still this method might help out in other situations)? We are...
  12. R

    Best way to match impedance between an amplifier and transducers

    I am trying to figure out the best way to match impedance values between an amplifier (50 Ohm) which powers a number of transducers (initially 50 Ohm but could change). For one transducer I have previously used a step up transformer (SUT) device between the amplifier and transducer. Now I have...
  13. H

    I Modifying EFE to Match Newton's Gravity Predictions

    Is it possible to reduce and/or modify the EFE so that they make the exact same prediction as Newton's law of gravity? I am wondering if the slight differences in prediction from these two mathematical approaches can be identified at a particular place in the EFE or if it's the geometrical...
  14. S

    Textbook says V=E/w but units don't match

    In my textbook, it is talking about the Hall Effect on a flat conductor with width w carrying a current i in a uniform magnetic field perpendicular to the plane of the strip. It says that this will create a potential difference of V=E/w where E is the induces electric field from the electrons...
  15. ORF

    Why is iron added to the head of a match?

    Hello, The explanation for this, min 0:54 is that you have Fe2O3 in the match head, and after burning it, pure iron is obtained 2 Fe2O3 + 3 C -> 2 Fe + 3 CO2 I think the chemical explanation is fine, but I don't understand why Fe2O3 is added (as colorant, if the red phosphorus is already...
  16. S

    Combining springs to match Force vs Extension Graph

    Homework Statement f Homework Equations Hooke's Law: F = -kx Series spring combinations: ##\frac{1}{k_{eq}} = \frac{1}{k_1}+\frac{1}{k_2}## Parallel spring combinations: ##k_{eq} = k_1+k_2## The Attempt at a Solution The slope of 1 is ##\frac{4}{5}## and the slope of 2 is ##\frac{3}{2}## I...
  17. F

    Insights Match the Scientist with the Story Quiz - Comments

    Greg Bernhardt submitted a new PF Insights post Match the Scientist with the Story Continue reading the Original PF Insights Post.
  18. MidgetDwarf

    Geometry Modern Geometry book to match my course description

    MATH 4300 - Modern Geometry (3) Prerequisite: MATH 3450 with minimum C grade. Topics selected from advanced Euclidean geometry, non-Euclidean geometry, projective geometry. May be repeated once for credit with approval of instructor as subject matter changes. The above paragraph is the course...
  19. Physics Dad

    Statistics question: Adjusting staffing levels to match customer traffic

    Hi, I have a very basic statistics homework question, and I have given it a go, but I just wanted to know if I had approached it correctly: QUESTION A shop adjusts its staffing levels using a model of customer demand through the week in the ratio of: 0.22(Mon); 0.14(Tue); 0.16(Wed); 0.18(Thu)...
  20. P

    Why don't units have match for specific heat and mass

    Homework Statement A problem will ask for an amount of substance in kilograms to be raised to a certain temperature and the specific heat be given in J/g*K. The amount of substance is not required to be converted to grams to match the units in the specific heat to get the correct amount of...
  21. A

    I Changing the ISS's orbital inclination to match the Moon

    What is the practical feasibility of changing the International Space Station's orbital inclination to match the orbit of the Moon? Major future missions beyond the Earth-Moon system (ie: space colonization) will likely require in-orbit assembly of components from multiple launches. And...
  22. Ghazanfar

    Solving F-N Tunneling Equation Unit Match Problem

    Hi, Everyone, Hope you are fine and doing great. I am new here and need to ask how can we match both sides of F-N tunneling equation in unit. I am attaching the equation, i am working on but i could not solve the unit match problem. if the left term has unit A/V2 then how can we solve 2nd...
  23. allanwinters

    Basically solved, Last coordinate does not match?

    Homework Statement Does the line with equation (x, y, z) = (5, -4, 6) + u(1,4,-1) lie in the plane with equation (x, y, z) = (3, 0, 2) + s(1,1,-1) + t(2, -1, 1)? Justify your answer algebraically. Homework Equations (x,y,z) = (x0,y0,z0) +s(a1.a2,b3) + t(b1,b2,b3) The Attempt at a Solution...
  24. R

    Discrete Fourier Transform (DFT) Matching

    Homework Statement Match each discrete-time signal with its DFT: Homework EquationsThe Attempt at a Solution I am mainly confused about Signal 7 and Signal 8. Signal 1 is the discrete equivalent to a constant function, therefore its DFT is an impulse (Dirac ##\delta##), so it corresponds...
  25. edguy99

    I Does the Chirality match the helicity?

    In trying to understand the Neutrino where it has mass and its chirality is the same as its helicity, I have always had trouble visualizing a particle. I recently ran into this particle. I believe the "the chirality is the same as helicity" as in one direction it would feed things through the...
  26. B

    Why the answer in book does not match the clue given

    Homework Statement An elevator ascends from the ground with uniform speed. At time ##T_1## a boy drops a marble through the floor. The marble falls with uniform acceleration ##9.8## m/s^2 and hits the ground ##T_2## seconds later. Fiind the height of the elevator at time ##T_1##. Clue : if...
  27. R

    Schools Which grad schools would be a match for me?

    Well this is my first time posting here, but I was hoping this could be a helpful resource for me. I am trying to plan out which graduate schools to apply to in the fall and was wondering if anyone knew which graduate schools would be a good match for me and which ones would be too big of a...
  28. YouWayne

    I Similar Polygon Comparison for School Project

    I'm working on a school project and my goal is to recognize objects. I started with taking pictures, applying various filters and doing boundary tracing. Fourier descriptors are to high for me, so I started approximating polygons from my List of Points. Now I have to match those polygons, which...
  29. D

    Hepa filter specifications/ blower match

    Greetings, I am new here I hope I don't come of rude by just posting like this, but I am in need of assistance. Im making an air purifier myself. It will consist of a fan(blower Hepa filter and active carbon filter. I have no problem with carbon filter and fan specifications matching, but I am...
  30. N

    Mesh and nodal analysis don't quite match, but why?

    Homework Statement [/B] Find I by mesh and nodal analysis Homework EquationsThe Attempt at a Solution ##V_{10}## is defined at the junction of ##Z_1##, ##Z_2## and ##Z_4##. ##V_{20}## is defined at the junction of ##Z_2##, ##Z_3## and ##Z_5##. ##0V## is defined at the junction of ##V_1##...
  31. AdrianMachin

    Engineering EE or ME? Which will match my personality more?

    Hi, guys. I'm in a dilemma of choosing either EE or ME. I've read numerous web pages on this issue and now I think I'm more passionate about EE and I'm more curious about it. I like ME only for more hands-on projects and more art related things such as design which I'm not bad in it. I'm very...
  32. D

    Do the Relative Permittivity and Refractive Index of Water Match Up?

    Many textbooks and online sources give the relative permittivity of water as about 80 and the refractive index as 1.33. If you use the definition of refractive index to find the speed of light in water, you will find v = c/n ~ 2.56e8 m/s. However, if you use the equation to find the speed of...
  33. Omish

    Pressure drop does not match theory

    I've modeled a U-Pipe with laminar flow. The pressure drop from Fluent is about 3 kpa , but by theory it should be about 6 kpa (checked several times and I'm sure) My mesh is very fine and boundary conditions are vel-inlet and pre-outlet and wall. Would you please help me with the problem?
  34. Guidestone

    Bending moment in an axis doesn´t match

    Hey guys, first of all, this isn't a homework question, I just want to know why the results are what they are. I've been trying t obtain the same numbers using moment equilibrium but they still don't match. This is the example: W are the forces applied by the gears in force-pounds. The gears...
  35. Danielm

    Calculating Winning Probability for a Chess Master in a Competition

    Homework Statement A chess master plays n games at a chess competition, each against a different opponent. Based on their past performances, we can estimate the probabilities of each opponent beating the master: p1, . . . , pn ∈ [0, 1]. Describe an algorithm, which given integer k returns the...
  36. V

    Modifying h(t) to Match New Tidal Data

    Homework Statement The function h(t) = 5 sin (30(t+3)) is used to model the height of tides. On a different day, the maximum height is the minimum height is -8 and high tide occurs at 5:30am. Modify function so it matches new data. Homework EquationsThe Attempt at a Solution Answer: h(t) = 8...
  37. Dusty912

    Match second-order differential equations with their y(t) graph

    Homework Statement The problem is in the picture. #17 I would have typed it but there are graphs that are needed for solving it. Basically trying to figure out which y(t) graph belongs to one of the sinusoidal forced equations with various parameters. Homework Equations euler's formula...
  38. Monoxdifly

    Arrange Mathematical Operation Using 0-9 to Match the Post Number

    In this puzzle, you use all integers from 0 to 9 to arrange a mathematical calculation whose result is the post number. There are only three rules: 1. No double posting 2. No approximation 3. No made-up variables Now since it is the first post here, let me do it first which results in 1...
  39. B

    MHB Kate's Chances of Winning a 5 Match Tennis Tournament

    The Probability of Kate winning a tennis match is 80%. If she enters a 5 match knockout tournament, find the chance of her: a) winning the tournament: Is simply 0.8^5 = 33% b) winning the tournament given she wins her first three games: Is the intersection of the two over the probability she...
  40. S

    Finding the Closest Match to a Theoretical Curve

    Hi guys, i have been tasked with matching the upper a theoretical curve (seen in the picture-blue) to the upper experimental part. So far in an attempt to do this i have tried changing a single parameter in the equation i used to generate the theoretical curve, so that the sum of the differences...
  41. R

    Match on water sustained by surface tension

    Homework Statement A match of length l=4cm is floating on the surface of the water from a glass. ( the water is at room temperature) If from on one side of the match we pour a few drops of soap, the match starts moving. In which direction is the match mooving and what force is acting upon it? (...
  42. L

    A Match Box.... differentiation question

    Homework Statement a match box consists of an outer cover, open at both ends, into which slides a rectangular box without a top. The length of the box is one and a half times its breadth, the thickness of the material is negligible, and the volume of the box is 25cm^3 . If the breadth of the...
  43. C

    Center of mass and center of gravity don´t match, why?

    For a tapered beam of constant density the center of mass is calculated as the mean of the mass distribution along the central axis, the center of gravity is calculated by getting the equilibrium of the angular moments to the left and right of a fulcrum moving along the horizontal beam. The...
  44. J

    How would you match up these Z-transforms?

    Homework Statement In Figure Q1b (on the next page), two plots display samples of the continuous-time signal uct(t) = sin(2πt) and two plots display samples of the continuous-time signal vct(t) = e −t sin(2πt). For each signal, the samples in the corresponding plots are obtained with two...
  45. shanepitts

    Units Mismatch in Analytical Mechanics Textbook

    In my Analytical Mechanics textbook it states that the terminal velocity of a spherical object, whilst taking the linear and quadratic terms into consideration, is vt=[(mg/c2)+(c1/2c2)2]1/2-c1/(2c2) The units don't seem to match here. Is this normal? This is not a homework inquiry, it for...
  46. P

    Medical Physics Residency backup plans

    So... I didn't get matched in the MedPhys residency match, and have no idea what to do with my life now. :oldconfused: Currently I'm busy freaking out and being fed up with school and medical physics in general. I graduate in May with my M.S. in medical physics, and have no real plans. eek. I...
  47. C

    WWF match idea involving a scientist

    I was watching some old WWF matches and what we need is some very smart people to fill the science and engineering community. Now hear me out as it is an idea. My reputation is to think outside the box but say for example HHH needed his slede or nick foley one of the greatest People of all...
  48. T

    Integration seems gaussian but the answer does not match

    Homework Statement -h^2/2m (sqrt(2b/pi)) e^(-bx^2) d^2/dx^2 (e^(-bx^2)) dx from - to + infinity Homework Equations I tried differentiating e^(-bx^2) twice and it came up weird , I positioned the values and finally cam up with (-2b sqrt(pi/2b)...is there any other way to do it ? The...
  49. Whovian

    Artin - domains don't seem to match

    This isn't a homework problem, but rather a bit of confusion regarding something in the textbook we're using; if this isn't the right place, feel free to move it. From Artin's Algebra pages 422/423 (slightly paraphrased): Let ##Q=\begin{bmatrix}1&\\3&1\end{bmatrix}##...
  50. W

    How Much Energy is Needed to Ignite a Safety Match?

    I saw a YouTube video where someone took nichrome wire and a high voltage source and managed to light a whole series of matches. I got me curious so I ran some numbers on how much wattage could be produced for a given length of nichrome wire and a given voltage. And assuming time is no issues...
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