Train Definition and 650 Threads

A train is a form of rail transport consisting of a series of connected vehicles that generally run along a railroad (or railway) track to transport passengers or cargo (also known as "freight" or "goods"). The word "train" comes from the Old French trahiner, derived from the Latin trahere meaning "to pull" or "to draw".Motive power for a train is provided by a separate locomotive or individual motors in a self-propelled multiple unit. The term "engine" is often used as an alternative to locomotive. Although historically steam propulsion dominated, the most common types of locomotive are diesel and electric, the latter supplied by overhead wires or additional rails. Trains can also be hauled by horses, pulled by engine or water-driven cable or wire winch, run downhill using gravity, or powered by pneumatics, gas turbines or electric batteries.
The track usually consists of two running rails with a fixed spacing, which may be supplemented by additional rails such as electric conducting rails ("third rail") and rack rails. Monorails and maglev guideways are also occasionally used.Passenger trains include passenger-carrying vehicles and can often be very long and fast. High-speed rail systems began expanding rapidly in the late 20th century, and this remains a major subject of further development. The term "light rail" is sometimes used to refer to a modern tram system, but it may also mean an intermediate form between a tram and a train, similar to a heavy rail rapid transit system.
Freight (goods) trains use freight cars (or wagons/trucks) to transport goods or materials (cargo). It is possible to carry passengers and freight in the same train using a mixed consist.
Rail cars and machinery that are used for the maintenance and repair of tracks, are termed "maintenance of way" equipment; these may be assembled into maintenance of way trains. Similarly, dedicated trains may be used to provide support services to stations along a train line, such as garbage or revenue collection.

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  1. E

    I When Does a Train Passenger Experience Complete Darkness in a Tunnel?

    Assume it’s extremely bright and sunny outside the tunnel, but very very dark inside the tunnel If you are a passenger riding in the “center” of the train , and the shutting and opening of each door (the tunnel entrance and tunnel exit door) happens very fast and occurs at a point where one...
  2. M

    Pendulum on moving train

    The problem and solution are, However, I don't understand why the answer is correct. I think that time should be dilated since ##\Delta t = γ \Delta t_0 = 2γ## where ##γ \geq 1## for ##v \geq 0##. Does anybody please know what I'm doing wrong here? Thanks!
  3. S

    S=u*t+a*t^2/2 VS ratio 1:2:3:5... t1/t10= ...

    Hello! I can do this task just using this formula s=u*t+a*t^2/2. But just saw an example where someone used this Galileo toerem. Here is task: "An observer stands on the platform at the front edge of the first bogie of a stationary train. The train starts moving with uniform acceleration and...
  4. Z

    B Speed of Light Reflection: Einstein's Train & Mirrors

    Hello Let's suppose we have 2 observers. One is in Einstein's train and one is outside. There are 2 mirrors: one inside the train and one outside. Speed of train is v Both observers emit light which reflects from both mirrors. What will be the speed of reflected light for both observers from...
  5. B

    Python BigGANModel -- Trying to train a model to generate images

    I am trying to train a model to generate images, I have a dataset of over 17K of men posing. I have been training my model for a few hours now and Sadly all I am getting is this: Also my d_loss=-9.79e+3 how is it Negative ? here is my code: # -*- coding: utf-8 -*- """BigGANModel.ipynb...
  6. ejacques

    Calculating Train Deceleration: Kid's Free Fall Time

    I think, since the train is decelerate the kid will fall off at free falling. the time for that is: y=0.5*9.8*t2 ⇒ t=√(2*y/g)=√(2*3/9.8)=0.8sec. Now i think i need to find what is the distance the train is doing in this time, but i can't figure this out.
  7. M

    Electric motor problem -- Power to accelerate a toy train

    For part (b), The solution is, However, if the acceleration was not constant during the 21 ms, then would the power required be larger? I believe the average power required would be larger because if the train started off at a lower speed and then speed up very rapidly towards the end...
  8. M

    Non-inertial observer inside train

    For part (c) of this problem, The solution is, However, how did they know that the fictitious force that acts on the mass until the string become taut (T = Ma from as observed by an observer at rest outside) has a magnitude of Ma (assuming that the observer has no communication with the...
  9. B

    I Train Simulation: Observer A and B Contradiction?

    I have not seen this exact configuration discussed. Observer A in middle of train. Observer B at station. Both A and B think the other is moving. Observer A synchronizes two clocks and puts one at each end of train. Lightning strikes both clocks stopping them when A passes B. B says...
  10. String theory guy

    Acceleration of a suitcase in an accelerating train after getting pushed

    I was doing one of MIT's 8.01.1x course and came across this question. In case 2, how would we be able to theoretically calculate the horizontal acceleration in this non-inertial frame? The course said that Newton's Law do not hold in accelerating frames. However, could we find the...
  11. BurpHa

    A greater force? (A train engine pulling two identical cars)

    My choice is C, which is "equal to." Here is my reasoning: The engine pulls on car 1, so car 1 is having a force acting on it, which pulls car 1 forward. Likewise, the same amount of force is applied on car 2 by car 1 by moving forward with the same amount of force from the beginning. So it is...
  12. raymondd

    Calculate velocity in a "simple electric train"

    How do you calculate the terminal velocity of the train moving in a coiled copper wire with two magnets attached to the polar ends? I have attached someone else's work I've found on the internet here and need help
  13. A

    Light beam fired in a moving train (relativity)

    1) really does not make sense to me. It is not clear to me how light could be reflected in multiple directions if the source is not a tilted mirror or another object with specific properties. I think the thought of the "point" P confuses me. Further, the fact that light travels in the opposite...
  14. morrobay

    Number of Waves/Crests in Tsunami Wave Train

    In the two hours the wave is traveling from event 1600km offshore to land would eight waves/crests be produced: 2hours/T=15minutes be correct ? Eight cycles = eight waves in the train. * I asked on another physics forum. No reply. "Tried" to register on several oceanography forums.
  15. R

    Understanding Velocity Addition Laws for People on Train & Ground

    I kind of just made up the questions. I realize this is a basic question but my knowledge of physics is very limited.q1 answer v_left_ball = v_left_ball - v_train v_right_ball = v_right_ball + v_train q2 answer To get the speed from Bob's frame I would use v_Bob = v_Bob + v_Alice To get the...
  16. L

    I How Fast Can a Magnet Train Go in a Circular Tunnel?

    I was wondering, if the magnet train is propelled by putting same polar magnet face each other at an angle and its natural magnetic property same pole repel, that's how it'spushing the train faster and faster...now what if we create a circular tunnel and have the train push itself and repel...
  17. A

    Ecommerce in a Long express train journey

    Summary:: Ecommerce in Long express train journey. Your views and opinion regarding this potential facility provided on one of the Long express train journey.
  18. anorlunda

    Scientists train goldfish to drive a fish-operated vehicle

    I'm speechless. Presumably other PF members won't be. :wink: https://arstechnica.com/science/2022/01/goldfish-can-learn-to-drive-and-navigate-terrestrial-environments/
  19. chwala

    How long must the timetable allow for the whole train journey

    The question is below; My approach; and kindly note that i am comfortable in using the si units. Here i used, ##60##km/hr = ##16.66666##m/s. For part (a), using the ##v-t## graph, ##→s_1##=(##\frac {1}{2}##×##180×16.666)##+(##\frac {1}{2}##×##60##×##16.666##) ##=1500+500=2000##m...
  20. chwala

    Find how fast is the train travelling at the end of the fourth minute?

    Find the questions and its solution below; Now would i be correct to use; ##v= u +at## where i considered ##v=33.3##m/s and ##u=16.67##m/s as the given average velocities between the two points in reference. Then it follows that, ##33.33=16.67 + 150a## ##→a= 0.11## We are told that ##a## is...
  21. L

    Determine the final train speed (mass and slinky on a train)

    A, the train speed up?
  22. D

    Waiting for a train in a subway

    (a) $$P(X≥10)=∫_{10}^∞10e^{−10x}dx=e^{−100}$$ (b) $$E(X)=∫_0^∞10xe^{−10x}dx=\frac{1}{10}$$ (c)$$\frac{10e^{−10}}{P(X≥10)}=10e^{100−10x}=\text{the new probability distribution for}\quad x≥10$$ $$E(X)=∫_{10}^∞10xe^{100−10x}dx=\frac{101}{10}$$😒 (d) imho it's unclear which "probability...
  23. S

    Cellular or smartphone calls / texts / data when on a moving train

    Do smartphone users get good cellular service as well as good cellular data while on a moving passenger train? This is assuming no wi-fi available.
  24. Bhawna L

    Sketching a graph of contaminants after a train crash

    I tried to graph this equation, but all I am getting is a straight line that is x=0. I don't understand what I am doing wrong.
  25. LCSphysicist

    Special relativity, a train and a light pulse

    i am having some hard time thinking about this problem: It is basically this: Imagine a bulb and a receptor distant L from each other (at the same axis x) inside a room, the roof of the room is at a height d from the bulb and receptor. Now you are at a train moving horizontally, parallel to...
  26. Mikasun1108

    Newton's First law of motion -- Boy jumping vertically on a moving train

    I'm not sure if my answer is correct but I think the answer is false. Thank you for your help :) -sun1108
  27. E

    B Solve My Train Dilemma: Can I Jump High Enough?

    Assuming I'm in a train moving at a very high speed. According to Newton if I jump up, I must land at the same place. But what if I had the aptitude/ability to jump very very high, will I be moving in the air and land at the same place.
  28. PainterGuy

    B When a bullet is fired from the back of train

    Hi, I was reading this article, https://science.howstuffworks.com/question456.htm, about firing a bullet from the back of train which is moving as fast as the bullet. The following is taken from the article mentioned above. So, ideally, the bullet will fall straight to the ground as it exits...
  29. S

    Speed of train car when sand spilling out from it

    I have several confusion about this question: 1) Since the sand spilling out downwards, it means that there is change in momentum in vertical direction (before the sand spills and after the sand spills) but no change in momentum in horizontal direction so no net force in horizontal direction...
  30. Einstein44

    Eddy currents in electromagnetic train

    I know that the magnitude of the eddy currents is proportional to the magnetic field, which means it should increase as I add more magnets. However I am unsure if this approach is correct.
  31. D

    Train deceleration traveling up hill

  32. P

    Can Maglev Trains Be Used for Exercise?

    Hi everyone, I'm an Italian High Schooler and I need a problem about maglev trains for the final exam. I apologize in advance if my english is bad or if I didn't follow some rules. I'm not native and new to this forum.
  33. Bix

    Why Does Calculating Train Engine Power Result in Different Values?

    How did you find PF?: Online [Thread moved from the New Member Intro forum, so no Schoolwork Template is shown] Hi. I'm new and am trying to solve a simple question 'Find the max power of a train engine traveling level at 50 metres per second if total resistance to motion is 30 KiloNewtons...
  34. LCSphysicist

    Simple problem about relativity and train

    I want to solve this question first using the train frame, and so going to the ground frame, but the things got wrong, so i would aprpeciate to know why. I mean, there is another ways to solve it, but i want to know where is the error here. Simply, in train frame the time elapsed between the...
  35. O

    How can I design a gear train to meet specific torque and RPM requirements?

    Hello, I'm after some advice/ clarification on some gear train design. This may just be a simple clarification Requirements I have a lead screw which needs to be supplied power by a Motor. This Lead screw must have 140Nm Torque to raise and lower the load, and must turn at 200RPM. The motors I...
  36. B

    Simulating a MAGLEV train with COMSOL

    So I am currently trying to model a MAGLEV train using COMSOL (high school research project). My project uses AC and DC motors as alternatives to the current maglev infrastructure and transportation. I first created a prototype through CAD Onshape, then created it in real life and applied my DC...
  37. brotherbobby

    Pendulum hung from the ceiling of a train

    (a) No, a person seated inside the train compartment will not be able to tell whether the train is accelerating on a horizontal track or moving uniformly up an inclined track by observing the plumb line. (b) I am assuming that both observers are not allowed to look "out" of the boundaries of...
  38. LCSphysicist

    Relativity problem -- A person walking in a train that is traveling at 3c/5

    "(a) How much time does this take in the ground frame? (b) What is the person’s speed with respect to the ground? (c) How much time elapses on the person’s watch?" I solved it, but i am with a doubt yet wrt to the letter b. We can find that the train length in the ground frame is 4L/5, so, why...
  39. LCSphysicist

    Confused about relativity and a train

    We can find the difference of time to light reach both clocks, it should be Lv/c², what i am confused is why the rear clock show a higher reading of the front clock. Ok, the light take longer time to travel and reach the rear clock, and here is the thing! What i am interpreting is: When the...
  40. Amrator

    Calculating Time Difference and Length Contraction in Train Overtaking Scenario

    a) So I think I solved a. "The length of B is such that A says that the fronts of the trains coincide with at exactly the same time as backs coincide." This tells us that in A's frame, B has the same length as A. So ##L_{observed}## in A's frame is simply ##L##. To obtain the proper length of B...
  41. Amrator

    Solving Special Relativity Problem with Train Walking

    I've gone back to review special relativity in preparation for GR. I apologize for the horrific handwriting. a) So the ground frame measures the length of the train to be contracted by ##\frac{4}{5}##. So ##L_G = \frac{4L}{5}##. To calculate the total distance the train travels in the ground...
  42. David Lewis

    B Einstein's Train: Light Travel Time Explained

    https://www.physicsforums.com/attachments/269029 Lightning strikes A and B simultaneously in the Embankment frame. M' sees the flash at B before the one at A. But if the flashes are simultaneous in the Train frame, does M' still see B before A?
  43. J

    Jumping on a Train: Tips and Advice

    Hi, In theory its a simple question. What am I missing?
  44. M

    Length of a Wave Train in Special Relativity

    I am confused about how to find the length of a wave train emitted within a time interval T and that is moving with speed c relative to a moving frame that is itself moving with velocity v. Apparently the answer is that the wave train's length is cT - vT, but I tried to plug in variables into...
  45. L

    Train deceleration and minimum stopping distances

    So my work includes using the acceleration formula a=delta v/t (Vrtf-Vrti)/a -> (0-54)/(-0.31) -> t=174 seconds I plug in 174 seconds to find the acceleration of the left train. and got -0.22m/s^2 I then used the displacement equation x=(1/2)at^2+Vo+So coming out with Xrt=4703m and Xlt=...
  46. K

    Discovering Train Friction: Measuring Aerodynamics on Rails

    Summary:: How can I measure the friction of a train with its rails and the air. How can I measure the friction of a train with its rails and the air. You can assume that the face of the train is like the picture below. If you need any specifications just let me know
  47. G

    Can a Simple Formula Estimate Train Energy Consumption?

    Is there some rule of a thumb formula, which would be able to calculate the energy consumption of a train, based on the following parameters: - mass of the train - its speed - inclination It can be a simple approximation. I would be grateful for any kind of reply.
  48. NTL2009

    Electrical A speed limiter for a Universal Motor in an old Lionel Train

    I have a "262 Lionel Line" O gauge train, from the early 1930's. It has sentimental value, my Father-In-Law (RIP) got it as a gift when he was about age 10. I've set it up each Christmas, a short track around the tree. But it is difficult to control, the gearing is high (it goes fast), so...
  49. T

    What happens to a ball thrown forward vs. backward in a moving train?

    Can someone answer this question? If I throw a ball forward and another one backward (opposite to the train's movement) in a moving train, do both balls land at an equal distance from the thrower? I suspect throwing a ball forward is the same as throwing it in a motionless train but what about...
  50. sigr

    B What Would Light Look Like If Train Moved at > Speed of Light?

    I am reading up on the special theory of relativity, and watched a video. In the video we have a train moving at ½ c towards a station, where an observer is waiting. The train's headlamp is on. How would the lamp's light appear to the observer? I was thinking that it¨'d appear to the observer...
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