Measuring Tension Between Train Carriages

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    Measuring Tension Train
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Discussion Overview

The discussion revolves around measuring tension between train carriages using a LEGO NXT unit as a model. Participants explore the implications of constant velocity and gravitational forces on tension, particularly when the train is moving up an incline. The conversation includes theoretical calculations and practical measurements, focusing on the relationship between tension and various factors such as mass and incline angle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant describes a practical experiment involving a LEGO NXT train pulling two carriages and seeks equations for calculating tension under constant velocity conditions.
  • Another participant suggests that if the train moves up the incline at constant velocity, the tension should be equivalent to that when stopped on the incline, prompting a question about analyzing this scenario.
  • A participant expresses confusion about how to approach the problem without acceleration, questioning how tension can remain the same on an incline compared to a flat surface.
  • There is a reference to a formula involving rolling friction, which one participant's engineer father provided, and a request for more information on its derivation.
  • Another participant discusses the addition of rolling resistance to gravitational force to determine the tension force, suggesting a simplified model based on weight distribution across wheels.

Areas of Agreement / Disagreement

Participants express uncertainty about the relationship between tension and incline, with some suggesting that tension remains constant while others question this assumption. There is no consensus on the calculations or the application of the formulas discussed.

Contextual Notes

The discussion includes various assumptions about forces acting on the system, the role of gravitational acceleration, and the impact of mass and incline angle on tension. Some participants reference specific formulas and conditions, but these are not universally accepted or clarified.

Who May Find This Useful

This discussion may be useful for students conducting experiments related to forces and tension in physics, particularly in the context of inclined planes and practical applications of theoretical concepts.

AviationFanBoy
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Im doing a prac for school that we have to create ourselves.
My groups prac goes along the line of a train pulling two carriages.
Our train is a LEGO NXT unit that runs at a constant velocity, no acceleration. We will have two force gauges between each carriage and the carriage and the train and test how the tension changes as we increase the mass and run them up a incline. We want to compare the real world figures to how the tension would be as calculated on paper.
Is there any equations that apply to no acceleration, constant velocity for calculating the tension?
Thanks.
 
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If the train is going up the incline at constant velocity (no acceleration), then the tension between the carriages should be the same as if the train were stopped on the incline.

Do you know how to analyze that situation?
 
Sorry, I am from Australia so I am not quite sure what should be known and not known at my level in the US. Typically with this type of question, where given an acceleration in which we can then solve the net force and subsequently solve the tension force. Thats the way i would normally approach it. Not sure how i would approach it if I've got a constant velocity as the acceleration would be zero and thus the net force would be 0. How so would the tension force between them be the same as on the flat? They are acting a different angles. And in different trials different masses.
 
Though you have no linear acceleration, you have gravitational acceleration acting down the incline.
 
Im aware of that. But how do i then put use that to calculate the tension force acting. Also, the prac was changed from two carriages to just one bigger one. I threw all the data, from the actual tension measurments from the prac in excel.
And my dad (an engineer) gave me the following formula which I am guessing is for some sort of rolling friction. (not we used frictionless surfaces).

F = Weight (normal) x friction coefficient x diatmer of axle)/diamter of wheel
x4 cause the trailer has 4 wheels.

Can anyone point me towards some more infromation for this formula, in particular the derivation. It work quite well when i calculated the tension using and they were quite accurate and similar to the ones i actually recorded in the prac.
 
Sorry for the delay in responding.
I guess you are adding the rolling resistance force to the gravitational force then.
(this is the tension force you need)
If you assume that the weight of the carriage is evenly distributed around all 4 wheels, things are simpler.
Get the rolling resistance force (f) in Newtons ( fixed, regardless of speed ) from:
f = m * g * ( cosine of incline angle ) * rolling resistance co-efficient
( m = carriage mass in kg, g = local gravitational acceleration in (m/s)/s )
 

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