What is Line: Definition and 1000 Discussions

Líně is a municipality and village in Plzeň-North District in the Plzeň Region of the Czech Republic. It has about 2,800 inhabitants. Líně lies approximately 11 kilometres (7 mi) south-west of Plzeň and 95 km (59 mi) south-west of Prague.

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  1. A

    Mathematica - How to Go to Next Line Without Running Process?

    I am trying to run multiple lines input in Mathematica in the free-form input. From everything I read online, you simply hit "enter", but hitting enter runs my process. Both enters, the one next to my letters, and the one on the numerical keypad. Hitting shift+enter also runs it. I can't...
  2. Euge

    POTW Integration Over a Line in the Complex Plane

    For ##c > 0## and ##0 \le x \le 1##, find the complex integral $$\int_{c - \infty i}^{c + \infty i} \frac{x^s}{s}\, ds$$
  3. F

    Ideal Straight Line Fit for a Temperature Sensor Output

    X 0 50 100 150 200 250 Y 120 178 201 249 303 364 XY 0 8900 20100 37350 60600 91000 X^2 0 2500 10000 22500 40000 62500 ∑X 750 ∑Y 1415 ∑XY 217950 ∑X^2 137500 M = (6*217950)-(750*1415) / (6*137500) - (750)^2 M = 1643 / 1750 M =...
  4. M

    B Basic Straight Line Permanent Magnet Accelerator

    I stumbled upon this video on YouTube: Here is a screenshot with some colored lines added of the part that generated a few questions in my head that I hope some of you smart folk can answer for me. In the video, the spherical magnet (at the end near the two big magnets) appears to increase...
  5. ARoyC

    Engineering Optimizing Diode Performance: Load Line Analysis

    I have drawn the I-V characteristic graph of the diode. I am facing problems with drawing the load line. For what value of E (Source Voltage), should I draw the Load Line? To get the I-V graph, I had to continuously change E.
  6. T

    Line of charge and conducting sphere (method of images)

    I was thinking of using the sphere and point charge as an analog, but is quite diferent from what i have seen
  7. C

    Finding line where two planes intersect

    For this problem, The solution is, However, I could not get that. By getting the system in REF, I got ##x = 3 + \frac{3}{7}z ## and ##y = \frac{1}{7}z##. Therefore z is a free variable so ##x = 3 + \frac{3}{7}t = 0## and ##y = \frac{1}{7}t##. Thus equation of line is ##x\hat i + y\hat j +...
  8. S

    I Smallest subspace if a plane and a line are passing through the origin

    Hi all, I am a beginner in Linear Algebra. I am solving problems on vector spaces and subspaces from the book Introduction to Linear Algebra by Gilbert Strang. I have come across the following question: Suppose P is a plane through (0,0,0) and L is a line through (0,0,0). The smallest vector...
  9. chiyu

    I Vector calculus: line element dr in cylindrical coordinates

    We were taught that in cylindrical coodrinates, the position vector can be expressed as And then we can write the line element by differentiating to get . We can then use this to do a line integral with a vector field along any path. And this seems to be what is done on all questions I've...
  10. C

    Limit problem involving two circles and a line

    For this problem, The limiting position of R is (4,0). However, I am trying to solve this problem using a method that is different to the solutions. So far I have got, ##C_1: (x - 1)^2 + y^2 = 1## ##C_2: x^2 + y^2 = r^2## To find the equation of PQ, ## P(0,r) ## and ##R(R,0) ## ## y =...
  11. CoNiss

    A Calculating Probability of N Points on a Line Being Within Given Distance

    Probability of any random n points on a line being within a given distance Hi, I am a software engineer trying to solve the following problem analytically given a line segment in cm and n random points on it what is the probability that the distance between any 2 consecutive points on the...
  12. LarryS

    I Transmission Line EM Wave vs EM Wave in Free Space

    According to Maxwell’s Equations, the speed an EM plane wave in free space, far from its source, is determined by the electric constant, ε0, and the magnetic constant, μ0, such that c = 1/√( ε0 μ0). The units of ε0 are capacitance per unit length and the units of μ0 are inductance per unit...
  13. D

    Q regarding fixing old busted water line w/ no water in it for 2 yrs

    Water line on a certain property has been busted for 2 years and no water in line. I am calling plumber tomorrow to get fixed and am just curious before I do that if fact that there has been no water in line would pose any particular issue to plumber just coming out and fixing that one spot...
  14. H

    Forces in a Line: Examining the Relationship Between Mass and Force

    Hello! In the following image, is it true that S1 = mg/2. Thanks for answears!
  15. Trysse

    B Constructing a Line Segment Equal to a Circle's Circumference?

    Is there any way to construct a line segment, that has the lenght of the circumference of a circle using only a ruler and a compass? My intuition says "no" Or phrasing the question in another way: given two line segments, can I prove, that the longer line segment has the length of the...
  16. paulimerci

    At what angle must the boat travel so that it moves in a straight line

    I'm assuming the boat is traveling north at an 8 m/s and the river is flowing east at a 2 m/s. For the boat to move in a straight line, it has to aim at an upstream angle given by #theta#. Using SOH CAH TOA, ##v_r = 2m/s##, ##v_b = 8m/s## $$\theta =\sin^{-1} \frac{v_r}{v_b}$$ $$\theta = 14...
  17. sachin

    Exploring Equation of a Straight Line in 3D Space

    Can we say, (y + z ) x1 = (y1 + z1) x is also an equation of a straight line in 3 dimensional space, where (x1,y1,z1) and (x,y,z) are the coordinates of a given point and a variable point respectively on a 3D line that passes through the origin, have seen equation of a straight line in 3...
  18. F

    Magnitude of the Line Charge Density of a Power Line

    Okay so I am a little confused as to where I made a mistake. I couldn't figure out how to program Latex into this website but I attached a file with the work I did and an explanation of my thought process along the way.
  19. V

    Discontinuity in an Electric line of force

    This is a tricky and difficult question for me. I know from reading various textbooks that electric lines of force are always continuous without breaks, but cannot pinpoint a reason for this. The only reason I can come up is that an electric line of force must always begin and end on charges...
  20. noowutah

    Find the electric field of a long line charge at a radial distance

    TL;DR Summary: Find the electric field of a long line charge at a radial distance where the potential is 24V higher than at a radial distance r_1=3m where E=4V/m. Answer: 29.5V/m. Never mind: I retract this question. The integral apparently is supposed to diverge! I apologize for not reading...
  21. M

    Lorentzian line profile of emitted radiation

    First of all i tried to follow the textbook. Here they start of by modelling the atom as an harmonic oscilator: Then they find the solution as: They neglect the second term as omega_0 >> gamma which also makes good sense so they end up with: So far so good. After this they state the...
  22. S

    The FBD Mystery: Why Isn't Normal Force Along Radial Line?

    so this is what the FBD is.... but to be fair, to me this one looks as if the normal force in the direction of the radial line, yet it isn't???? here in the solution, it's not along the radial line, whys that???
  23. S

    Angle between normal force and radial line for cylindrical coordinates

    so I was wondering. there is this normal force on the can from the path. And there's this formula to find the angle between the radial line and the tangent or also between the normal force and either the radial or theta axis. the formula is ##\psi = r/dr/d\theta##. The thing is that here they...
  24. dom_quixote

    B Geometric Issues with a line, a plane and a sphere...

    I - A point divides a line into two parts; II - A line divides a plane into two parts; III - Does a smaller sphere divide a larger sphere into two parts, like layers of an onion? Note that the first two statements, the question of infinity must be considered. For the third statement, is the...
  25. tracker890 Source h

    Question about source flow rate across line AB.

    Q:Please hlep me to understand which ans is correct.To determine the flow rate in Line AB. $$\mathrm{Known}:V_A,q,r_A = constant.$$ so/ select:## A,{B}^{\text{'}},B,A,## is control volume $${Q}_{AB}={Q}_{A{B}^{\text{'}}}=\iint _{A}^{}({V}_{A})dA={\int }_{{\theta }_{A}}^{{\theta...
  26. Anyname Really

    Position pointer to specific line in a file

    I would like to read a specific line of a file. Everything I have seen does it by reading the file from the top, ignoring what is read until the line of interest is reached. Is it possible to move the pointer of the reader to the line directly, say by counting the number of line end sequences...
  27. kyphysics

    Landline Phone Q: Why is the phone line plugged into modem-not wall?

    In the old days, people plugged landline phones into house/apartment wall mounted phone jacks. This was standard. Then, at some point, people started plugging their landline phone cords (via an adapter) into their internet modems. Dumb question for a non-techie. Why is that? Also: a.)...
  28. WMDhamnekar

    Computing line integral using Stokes' theorem

    ##curl([x^2z, 3x , -y^3],[x,y,z]) =[-3y^2 ,x^2,3]## The unit normal vector to the surface ##z(x,y)=x^2+y^2## is ##n= \frac{-2xi -2yj +k}{\sqrt{1+4x^2 +4y^2}}## ##[-3y^2,x^2,3]\cdot n= \frac{-6x^2y +6xy^2}{\sqrt{1+4x^2 + 4y^2}}## Since ##\Sigma## can be parametrized as ##r(x,y) = xi + yj +(x^2...
  29. person123

    Saudi Arabia's "The Line" -- why?

    I just found out about Saudi Arabia's "The Line", and I don't want to mock it with my very limited knowledge (I honestly would have thought it was satire), or bring up politics behind it, or go into its lofty goals like 100% clean energy or life enhanced by AI. To me, the first question is just...
  30. E

    Waves- sending a pulse across a weighted line

    Here is a picture of the problem: I honestly am pretty lost, I'm not looking for an answer, more so an idea to get me started. But here is what I was thinking: In the equation above I was trying to use: For U I am unsure how to incorporate the weight of the blocks into the u, so I am unsure...
  31. Lluis Olle

    B Metric Line Element Use: Do's & Don'ts for Accelerated Dummies?

    From Wikipedia article about Hyperbolic motion, I have the following coordinate equations of motion for Bob in his accelerated frame: ##t(T)=\frac{c}{g} \cdot \ln{(\sqrt{1+(\frac{g \cdot T}{c})^2}+\frac{g \cdot T}{c})} \quad (1)## ##x(T)=\frac{c^2}{g} \cdot (\sqrt{1+(\frac{g \cdot T}{c})^2}-1)...
  32. Euge

    POTW Uniformly Continuous Functions on the Real Line

    Let ##f : \mathbb{R} \to \mathbb{R}## be a uniformly continuous function. Show that, for some positive constants ##A## and ##B##, we have ##|f(x)| \le A + B|x|## for all ##x\in \mathbb{R}##.
  33. WMDhamnekar

    Evaluate the line integral

    Author's answer: Recognizing that this integral is simply a vector line integral of the vector field ##F=(x^2−y^2)i+(x^2+y^2)j## over the closed, simple curve c given by the edge of the unit square, one sees that ##(x^2−y^2)dx+(x^2+y^2)dy=F\cdot ds## is just a differentiable 1-form. The...
  34. Marah Elisabeth

    Power Line Dangers: Is My RV Safe?

    There is a power line of undetermined voltage hanging just 4 feet above my RV and the stream running next to us. If during the rain, a branch from the redwood tree above us falls and causes the hot line to land on the RV and stay there, is there a way to prevent us being shocked while we try to...
  35. Elementard

    Is it possible to solve this problem without using integrals or derivatives?

    t=0 => v(0) = 4(0) - 3(0)^2 = 0m/s t=2 => v(2) = 4(2) - 3(2)^2 = -4m/s Vavg => (v(0) + v(2))/2 = -2m/s When researching the answer, I noticed that they used integrals to solve this question. The only problem is that we never learned about integrals/ derivatives or anti derivative. Is there any...
  36. G

    Find the two points on the curve that share a tangent line

    IMPORTANT: NO CALCULATORS I assumed two points, (a, f(a)) and (b, f(b)) where b is greater than a. Since the tangent line is shared, I did f'(a) = f'(b): 1) 4a^3 - 4a - 1 = 4b^3 - 4b - 1 2) 4a^3 - 4a = 4b^3 - 4b 3) 4(a^3 - a) = 4(b^3 - b) 4) a^3 - a = b^3 - b 5) a^3 - b^3 = a - b 6) (a...
  37. Demystifier

    I Geometries from Line Element $$dl^2=d\theta^2 + \sin^2\theta\, d\varphi^2$$

    Consider the line element $$dl^2=d\theta^2 + \sin^2\theta\, d\varphi^2$$ where ##\theta\in [0,\pi]##. The standard interpretation of this line element is to take ##\varphi\in [0,2\pi)##, in which case the line element represents the standard metric of the sphere ##S^2##. However, from the line...
  38. M

    Gauss' law in line integral, Q=##ϵ_0 ∮E.n dl=-ϵ_0 ∮∂ϕ/∂n dl##

    I know the Gauss law for surface integral to calculate total charge by integrating the normal components of electric field around whole surface . but in above expression charge is calculated using line integration of normal components of electric field along line. i don't understand this...
  39. T

    Why 80% of Americans Live East of This Line

    A 20 minute video exploring Population Density, Topography, Orography, and Rainfall. The narrator is a bit annoying but there is a lot of information in it.
  40. M

    Precise definition of tangent line to a curve

    How do we define tangent line to curve accurately ? I cannot say it is a straight line who intersect the curve in one point because if we draw y = x^2 & make any vertical line, it will intersect the curve and still not the tangent we know. Moreover, tangent line may intersect the curve at other...
  41. chwala

    Find the equation of the regression line of ##x## on ##y##

    The question is as shown below. ( Text book question). The textbook solution is indicated below. Discussion; Now they seemingly used ##r=1## to arrive at ##x=0.8+0.2y##. That is, ##y=-4+5x## then, since ##r=1##, ...implying perfect correlation therefore, ##5x=4+y## ##x=0.8+0.2y## My other...
  42. H

    Help with a line integral please

    ∫zds=∫acos(t)*( (acos(2t))^2+(2asin(t))^2+(-asin(t))^2 )^1/2 dt , (0≤t≤pi/2) Simplified : ∫a^2cos(t)*(cos^2(2t)+5sin^2(t) )^1/2 dt , (0≤t≤pi/2) However here i get stuck and i can´t find a way to rewrite it better or to integrate as it is. Can i please get some help in this?
  43. H

    How to find the straight tangent line?

    I have solved the gradient: gradf(2,-1)=(4,2) and have the tangent plane: 4x+2y+3=0 Somehow the answer is: 3=2x+y And i really don´t understand why.
  44. P

    Calculating eletric potential using line integral of electric field

    So, I am able to calculate the electric potential in another way but I know that this way is supposed to work as well, but I don't get the correct result. I calculated the electric field at P in the previous exercise and its absolute value is $$ E = \frac {k Q} {D^2-0.25*l^2} $$ This is...
  45. A

    Confusion about the equation of a line in space (vector form)

    Hi, In my calculus book,I found this vector form of line equation in space (bold means vector): Given point (x1,x2,x3) lies on line L & v=<a,b,c>, then equation of line is : r = <x1,x2,x3> + t <a,b,c> with t any number. Now, my question if I plug any number for t, then result will be vector...
  46. Melbourne Guy

    Are we predisposed to run along the line of a falling tree?

    We have trams in Melbourne, and this weekend I watched a pigeon on the tracks fly up and along the route as the tram came along, being hit by the windscreen (it survived, no worries). Yet it could of flown up and across and escaped because the tram was higher than it was wide. It prompted the...
  47. M

    A Confusion of the scale of contact line dynamics and capillary flow

    I'm having some trouble getting my head around the scale at which capillary flow and contact line dynamics are important. In the simple case of liquid rise in a capillary tube, a smaller tube will allow for greater rise since a larger height is required to achieve an equal weight of the liquid...
  48. J

    Moving in a straight line with multiple constraints

    Hi All, I am trying to solve what I think should be a simple problem, but I must be missing something because I am struggle to solve it. The situation is shown below: So to summarise: A body starts at Point A It moves in a straight line to Point B, covering a distance of 10m The time taken...
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