What is the Force Constant k of a Spring?

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Homework Help Overview

The problem involves a subway train coming to a stop using a spring bumper, with a focus on determining the force constant k of the spring. The context includes concepts of kinetic and potential energy in relation to spring mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between kinetic energy and potential energy in the context of the spring. Questions are raised about how to apply the potential energy formula for springs and the initial kinetic energy of the train.

Discussion Status

Some participants have offered guidance on the relevance of potential energy concepts, while others express uncertainty about how to apply the equations correctly. Multiple interpretations of the energy conversion process are being explored.

Contextual Notes

There is a mention of the conservation of energy principle, and participants are questioning the initial conditions and how they relate to the final state of the system. The original poster indicates a discrepancy in their calculations, suggesting a need for further clarification.

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Homework Statement



A 4.50 ✕ 10^5 kg subway train is brought to a stop from a speed of 0.500 m/s in 0.900 m by a large spring bumper at the end of its track. What is the force constant k of the spring?

M- 4.50E5 kg
IV- .5m/s
FV- 0m/s

Homework Equations


k=mg/x
F=-kx
PE = (.5)kx^2

The Attempt at a Solution


k=(450000kg)(9.81m/s^2)/ .9 = 4900000, which isn't the right answer. Can someone help me out?
 
Last edited:
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Have you read anything about the concept of potential energy of a spring?This question is directly based on that..
The kinetic energy of the train is being converted in the potential energy of spring?
 
Well I know PE = (.5)kx^2, but I am afraid I don't know how to plug in the numbers.
 
What's the intial kinetic energy (KE) of the train?
KE will = 0 when v = 0 (why is this true?)
Due to conservation of potential energy, initial(KE+PE) = final(KE+ E)
 

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