What is Multiple: Definition and 1000 Discussions

A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train control.
Although multiple units consist of several carriages, single self-propelled carriages - also called railcars, rail motor coaches or railbuses - are in fact multiple-units when two or more of them are working connected through multiple-unit train control (regardless if passengers can walk between the units or not).
The term multiple unit does not denote locomotives using multiple-unit train control.

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  1. G

    System of multiple conductors: image method

    Homework Statement The following figure represent the traversal cut of a system with two cylindrical equal conductors of radius r0 length l at a distance d from one another and at the same distance h of a plane conductor (conductor zero). The dielectric that surrounds the conductors is the air...
  2. B

    B Multiple Curves in Space-Time: Masses on a Trampoline

    When you put a mass on a trampoline it causes the trampoline to V. If you put another similar or same sized mass on the same trampoline at a great enough distance, will the curve on the trampoline/space-time look like a W or a U ? If you can get the curves on a trampoline/space-time to look...
  3. M

    Python How to compute the percentage of values based on multiple columns

    I have a dataframe as shown in the picture and what I am trying to do is to calculate the number of occurrences based on the values in 2 columns and then calculate the percentage of the occurrences. I have tried the following code but it gives me a zero value in the end and i don't know why...
  4. M

    Is (3/4)*(a^2/c) less than a with multiple inequalities?

    Homework Statement I for some reason can't seem do become sure of this. There are 2 variables x and y. And two constants, a and c, which are both positive. Homework Equations x+2y ≤ (3/4)*(a^2/c) x + 2y < a The Attempt at a Solution Does this mean that: (3/4)*(a^2/c) < a ? Mons
  5. A

    MHB Reference request for self-studying multiple Riemann integrals

    As the title says, I would like to self-study multivariable real analysis (integration, specifically; the Riemann integral) and I need some recommendations (resources, books, videos, ...). I'm from Croatia and got my hands on some Croatian notes about multivariable real analysis so if some of...
  6. S

    MHB Calculating overall percentage/probability from multiple categories?

    Greetings, My apologies if the title is confusing; I don't really know how to explain what I am trying to do or what label this problem would fall under. Scenario: We have a magic bag, and inside the magic bag are an unknown/unlimited amount of coins. There are 100 different types of coins...
  7. A

    I Identity Operator for Multiple Particles

    Hi, For a particle in a box (so that the momentum spectrum is discrete), we can write the identity operator as a sum over all momentum eigenstates of a projection to that eigenstate: $$I=\displaystyle\sum\limits_{p} |p\rangle\langle p|.$$ I was wondering what the corresponding form of the...
  8. Krushnaraj Pandya

    Analyzing a circuit with multiple batteries

    Homework Statement Find charge on 3 capacitors. Join two squares with one common side. At the middle of the common edge, place C3=6uF (micro-farad). On upper edge of left square, place C1=2uF. On upper edge of right square place C2=4uF. On lower edge of left square, a battery-10V and on lower...
  9. R

    How do I stop multiple radio frequencies ....Micro, Infra an

    How do I stop multiple radio frequencies ...Micro, Infra and combined frequencies used in a sweep rotation(?? guessing here) ...from any space. Thank you for any advice you can give. Been traveling. For the record I thought...wearing magnets ?? I have some minimal back ground in RF but am a...
  10. Alex Petrosyan

    Physics Getting into theoretical Physics after multiple setbacks

    Hi all, I'm a theoretical physics hopeful, and I've had a couple of major setbacks in my undergraduate studies. I'm thinking of whether I should pursue a career in TP, or reconsider doing physics entirely. My background: I've always had an interest in Physics. I got a bronze medal from...
  11. Grey Area

    Bernoulli effect in multiple channels

    Hi al;l, it's Mr. ALKIADT again (A Little Knowledge Is A Dangerous Thing)...in this case, my knowledge of Bernoulli effect. I know that when a fluid passes through a restriction, the flow rate speeds up to maintain the flow rate of the wider cross sectional area behind it...so if you've got one...
  12. P

    Multiple processes interpretation

    Hi pf, there was an article in the Stanford encyclopedia about QM that was rewritten. it quoted a "multiprocess" interpretation differing from Everett's one which could be related to Bohm's interpretation. it is no more there. i am wondering if there are interpretatins where different results...
  13. Sophrosyne

    B How does the ear distinguish multiple different pitches?

    A chord played on a piano is multiple different pitches, each at a different frequency, played simultaneously. The ear hears this as separate sounds. The cochlea of the ear is organized by tone (tonographic organization), from highest to lowest frequency. So a triad chord will stimulate three...
  14. mishima

    I Test for dependence/independence of multiple variables

    I don't think this is related to linear dependence/independence of linear algebra. I am talking about multi-variable calculus. I am getting confused with being able to quickly tell which variables depend on others when there are 4+ variables involved. For example, suppose I have w(r,s)...
  15. E

    I Helmholtz resonator with multiple necks--formula?

    Does anybody happen to know the formula for resonant frequency of a Helmholtz resonator having N necks? Physics is not my field and I'm a bit over my head. I need the formula for a computer program related to musical instruments--this is the only thing holding me up. It seems like it would...
  16. M

    MHB Explore the Multiple Grid Method: Get Accurate Solution Faster

    Hey! :o I am trying to understand the multiple grid method. The idea is to use at each step different grids to solve a linear system of differential equations, so that we get the best approximation as possible. It holds that the finer the discretization, the more accurate the solution ist...
  17. PeterDonis

    A Does the MWI require "creation" of multiple worlds?

    From another thread: I see this claim made fairly often, but it does not seem correct to me. According to the MWI, the dynamics of the wave function is always unitary (there is no collapse), and a unitary process cannot "create" or "destroy" anything. All it can do is entangle things. So, for...
  18. D

    Multiple choice on uncertainty

    1. A student measures the density of a metal and calculates answer to be 8543.2kgm^-1 . The result is accurate to +- 1.1% Which of the following states answer to an appropriete number of sig figs? A 8.543x10^3 B 8.5x10^3 C 9x10^3 D 8.54x10^3 2. Relative Uncertainty = Absolute Uncertainty/...
  19. Pencilvester

    I Number of Geodesics Between Two Points: Topology vs. Homeomorphism

    In general, is the number of distinct geodesics between two fixed points purely a feature of the topology of the manifold? i.e. Can there ever exist two topologically equivalent (I can’t remember the proper word right now- is homeomorphic the right one?) manifolds, ##\mathcal M## and ##\mathcal...
  20. EF17xx

    Standing wave in a tube -- multiple choice question

    Homework Statement The correct answer according to answer sheet is answer B. Homework Equations λn= 2L/n (both ends open) λn = 4L/n (one end open one end closed) c=λf Speed of sound does not change. as it is still in air... (correct assumption? ) The Attempt at a Solution f1= 500Hz L =...
  21. EF17xx

    Why is D the correct answer for this multiple choice question?

    Homework Statement Homework Equations Fnet= Δp/Δt p=mv The Attempt at a Solution p (before) = 0.4 x 5 = 2 p (after) = 0.4 x 3 = 1.2 Δp = 0.8 Δt = 0.2 Fnet= Δp/Δt 0.8/0.2 = 4N Correct answer in textbook is D, I do not understand why?
  22. alijan kk

    Complex number multiple choice

    Homework Statement If Z= (1)/(z conjugate) then Z : ? Homework EquationsThe Attempt at a Solution let z= a+bi the z conjugate= a-bi (a+bi)=(1)/(a-bi) (a+bi)(a-bi)=1 a2+b2=1 does it tell from this expresssion that the complex number is a pure real ?
  23. Z

    Impulse: multiple choice question

    Hi all Can anyone please help me with Q14 (attached) as you can see I am getting 167000N however the correct answer is 83000N Many thanks ZanyZoya
  24. Y

    Scalar in terms of multiple variables, Nyquist & Bode Plot

    Homework Statement A scalar is given by It is controlled by With step time h = 0.2 s 1. Find the discrete equivalent model 2. Check the stability of closed loop (K = +1) 3. Obtain the via the Bode plot Homework EquationsThe Attempt at a Solution So for question 1. This is where I'm...
  25. Buckethead

    B Spiral galaxies: Multiple axies of rotation?

    Spiral galaxies of course rotate around one axis perpendicular to the plane, but has anyone measured if any spiral galaxies are also rotating about an axis through the plane or about any other axis?
  26. J

    Heat Transfer through multiple walls

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  27. B

    MHB Predicate logic with multiple quantifiers

    Hello everyone. This is my first post on this forum. Thank you for taking the time to help me with my question. I have no idea where to start. :( Question 1: Find an example of a predicate P(x,y) where the domain of x and y are D such that $\forall x \in D, \exists y \in D, P(x,y)$ is true but...
  28. Jonathan Scott

    Implausible multiple failures in my gas central heating system

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  29. Observeraren

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  30. Jay1298

    Motor combination to drive multiple tyres

    If I need 50,000 Nm of torque to rotate a wheel, and I am rotating it about its rim (like the London eye), would 5 10,000 Nm motors each connected to a set of tyres to rotate it (the motors are not connected to each other), or would these motors first need to be connected to each other and then...
  31. C

    I Time Delay on Multiple Photons when travelling from one plac

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  32. Prof. 27

    System.Threading Multiple Timers in C#

    Homework Statement Basically I'm trying to create two timers using System.threading.timer that run in parallel. One that runs for a minute, one that runs for a second. When I run the program I get nonsensical output. Despite reading a lot of stack overflow questions I can't seem to find where...
  33. I

    MHB And rule for multiple selections

    Hello all I'm new as I'm just revising my maths to teach irish leavers in revising and exams maths and sciences. This exam section has me puzzled hope you can help Three digit numbers are made from the numbers 2,3,4,5,6 .. See questions and my calls below Total number of outcomes is ...
  34. B

    Electric field in a capacitor with multiple dielectrics

    Hi, I am trying to understand capacitors and have come across the example in the attached image. What I would like to understand is how to calculate the electric field at some distance x within the capacitor. With x>>R , x<R and x=R . The image is of two circular disks as the...
  35. Wookbert

    Holding down steel plate w/ multiple magnets: Does orientati

    The picture below shows an image of a bed from a 3d printer, which I intend to equip with an array of 15 x 3 mm Neodym magnets to hold down a steel plate. The steel plate itself is not and can not be equipped with magnets. Theres a heated aluminium bed between magnets and steel plate and the...
  36. paulo84

    B Rates of Change and Multiple Dimensions

    OK, so time is change of displacement. Speed is change of change of displacement. Acceleration is change of change of change of displacement (or of distance, sorry I'm not sure whether acceleration is a vector or a scalar). Then you get change of change of change of change etc. ad infinitum. It...
  37. R

    Magnetic field of solenoid and a coil with multiple turns

    Hi!, I have a question for you geniuses (geniusi?) Why are there two different equations to find the magnetic field of a solenoid and a coil with multiple turns? (According to my textbook) The equations for each are Solenoid: Coil with multiple turns: Why are they different? Is there a...
  38. J

    EMI Multiple choice question

    Homework Statement More than one options may be correct . Homework EquationsThe Attempt at a Solution [/B] Options a) and c) are correct . But I don't understand how non magnetic metal reacts to the magnetic field . Is it in some way related to ferromagnetism ? But then either both b)...
  39. J

    AC circuit Multiple choice question

    Homework Statement More than one options may be correct . Homework Equations Inductive reactance =ωL Capacitive reactance = 1/ωC The Attempt at a Solution On increasing the frequency , inductive reactance increases whereas capacitive reactance decreases . Thus , option a) is correct ...
  40. Y

    Angular momentum multiple choice question

    Homework Statement Hello, Here is a multiple choice question I would like to be clarified. Suppose that the angular momentum of a system can take the values 0, 1, 2. One carries out a measurement of ##J_z##,the state of the system will: ##a##-Be perfectly known if the result is 0 ##b##-Be...
  41. K

    I Designing a Car with Multiple Boxes: Free Body Diagrams

    hi, i am studying about design the box carried on car. i am really stuck in how to draw free body diagram for when 3 or more boxes stack together on car running and braking. there are many example with 2 boxes but i don't know why i can't find any case with 3 or more boxes thanks in advance
  42. mfb

    B Multiple supernovae from a star

    iPTF14hls was a supernova discovered in 2014. Typically they reach a brightness peak quickly and then fade over few months - but this star had several oscillations in brightness. To make it more confusing, archives from 1954 show a supernova at the same spot. News article This model can lead...
  43. ang__

    How Do You Calculate the Total Inertia Matrix for a Composite Object?

    Homework Statement The object is made out of multiple parts. The inertia matrices of every part are given. Only one part is rotating. How do I find the total inertia matrix. Homework EquationsThe Attempt at a Solution I thought that I could sum the inertia matrices, after tranforming them to...
  44. D

    Centering a Laser Beam received from multiple directions

    Is it possible to set mirrors up in such a way that if you hit any area of any of the mirrors, the laser would be brought to a central location in the middle of the mirrors? I'm thinking of a way to transmit data in space via laser where you would want a large target for the laser to hit when...
  45. A

    I Can a supernova produce multiple stars?

    Can a supernova produce some number of stars after it explodes or will it always produce just one, single star? Can the matter it ejects form multiple stars and solar systems or will there always be just one new star and its only new solar system?
  46. R

    Integrating Multiple Solid Volumes: xy-Plane, x=1, x=3

    Homework Statement A solid is bounded by the surface z=x^2-y^2, the xy-plane, and the plane x=1 and x=3. Compute, by double integration, the volume of the the solid. Homework EquationsThe Attempt at a Solution I know that the height is the z function and the lower limit of is x= 1 and upper...
  47. C

    MHB What is an Integral Multiple of 4?

    Dear Every One, I have a question: What does an integral multiple of 4 means?Thanks Cbarker1
  48. P

    Optimal Path from source to multiple destinations

    Homework Statement You are placed in a 2-dimensional labyrinth at a starting location ##s## and must travel to n goal locations ##g_1, g_2, ..., g_n##. Determine the optimal path using the A* algorithm. g = goal cell, s = start cell example input: 3 11 //row length, column length # # # # # # #...
  49. F

    A Differential of Multiple Linear Regression

    Say you have a log-level regression as follows: $$\log Y = \beta_0 + \beta_1 X_1 + \beta_1 X_2 + \ldots + \beta_n X_n$$ We're trying come up with a meaningful interpretation for changes Y due to a change in some Xk. If we take the partial derivative with respect to Xk. we end up with...
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