Calculating Force Exerted by a Moving Train on a Track

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Discussion Overview

The discussion revolves around calculating the force exerted by a moving train on a specific spot on a track. Participants explore the implications of the train's weight, the distribution of that weight across the wheels, and the potential effects of the train's velocity on the force exerted.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests calculating the force as the weight of the train multiplied by gravity, questioning whether the entire weight of the train exerts force on a single point.
  • Another participant proposes dividing the train's weight by the number of wheels to find the force per wheel.
  • A different viewpoint emphasizes dividing the weight by the contact area with the ground to determine the pressure exerted.
  • There is a query about whether the train's velocity affects the force exerted on the track.
  • One participant notes that while the weight per wheel can be calculated, it assumes a homogeneous train and states that the velocity does not influence the force since it acts perpendicular to gravity.
  • A participant provides specific weight estimates for freight cars and calculates the stress on the track based on assumed contact area, relating it to the compressive stress limit for steel.

Areas of Agreement / Disagreement

Participants express differing views on whether the velocity of the train affects the force exerted on the track, with some asserting it does not while others raise the question. There is no consensus on the impact of velocity or the assumptions regarding the homogeneity of the train.

Contextual Notes

Assumptions about the uniformity of the train's weight distribution and the nature of the contact area are not fully resolved. The discussion also includes estimates and hypothetical values that may not reflect all real-world conditions.

NAP2626
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Hey I was hoping some would be able to help me or show me how to calculate the amount of force a train exerts on a spot on a track.

Simply I could calculate the force exerted on a spot of the track as the weight of the train in kgs times the gravity (9.8m/s^2) will give me netwons of force.

But... I want to know if trains are moving and also can I assume the whole weight of the train exerts on that point??

thanks for any help
 
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You'll just need to divide by the number of wheels.
 
You need the weight of the train (its mass times g) divided by the total area that is making contact with the ground.
 
ok, what about the moving portion or velocity of the train, will that alter the amount of force exterted down on the spot?

Ok by dividing by the number of wheels I can assume that fraction of the trains weight ( that amount of weight per wheel )is focused on that small spot?

Thanks guys for the help
 
well you can find the weight that each wheel must support, however that assumes a homogenous train. The velocity of the train would have no effect. It is directed in a direction perpindicular to gravity (assuming the train is on a flat track)
 
I think a freight car weighs about 130 tonnes (tonne-wt)= 1.275 x 10^6 Newtons (engines are heavier). This weight is supported by eight steel wheels, so the weight per wheel is about 1.59 x 10^5 Newtons. There are about 100 cars in a typical freight train, so there are about 400 wheels, each with this weight, rolling over every piece of track every time a freight train goes by. Suppose the total area under each wheel supporting the load is 10 cm^2 (guess). Then the compression pressure (stress) is 1.59 x 10^5 Newtons/.001 meters^2 = 159 megaPascals (MPa). This about the allowable compressive stress limit for steel.
 
Last edited:
cool thanks
 

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