Pushing spring from both sides - Find the spring constant

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Homework Help Overview

The discussion revolves around a problem involving a spring with a relaxed length of 0.5 meters that is compressed to 0.4 meters by forces applied from both sides. Participants are tasked with finding the spring constant, k, given that the outward force exerted by the spring is 3 Newtons on each side.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of forces and the resulting compression of the spring. There is an exploration of the relationship between the total force applied and the total change in length of the spring. Questions arise regarding the interpretation of the spring constant and the definition of compression in relation to the forces applied.

Discussion Status

Some participants have provided clarifications regarding the definition of the spring constant and the relationship between force and compression. There is acknowledgment of confusion regarding how to correctly apply the concepts to the problem, and some participants express a better understanding after receiving guidance.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. There is a specific focus on the definition of the spring constant and how it relates to the forces and compression involved in the scenario.

Pishard
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Homework Statement


A spring relaxed length is 0.5[m]. It is being pushed from both sides, and contracted to 0.4[m]. The force the spring is applying outwards is 3[N] on each side. What is the spring constant k?

Homework Equations

The Attempt at a Solution



I attempted drawing a force diagram, and then getting the equations out of it, but I got that the constant is 60 (6=0.1k - because total of force is 3+3=6[N]), although I know it is 30, but I can't get it right using the diagram and equations. What am I doing wrong?

Thanks!
 
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Pishard said:

Homework Statement


A spring relaxed length is 0.5[m]. It is being pushed from both sides, and contracted to 0.4[m]. The force the spring is applying outwards is 3[N] on each side. What is the spring constant k?

Homework Equations

The Attempt at a Solution



I attempted drawing a force diagram, and then getting the equations out of it, but I got that the constant is 60 (6=0.1k - because total of force is 3+3=6[N]), although I know it is 30, but I can't get it right using the diagram and equations. What am I doing wrong?

Thanks!

Could you compress a spring by applying a force only on one side?
 
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PeroK said:
Could you compress a spring by applying a force only on one side?

True, I have to apply force on both sides. So in the equation F=-kx, the x meaning the total change of spring length.
Thanks!
 
Pishard said:
True, I have to apply force on both sides. But I am still confused, how do I know that the change in length on one side isn't half of the total, in this case half of 0.1[m]? Why it's 3=k*(0.1), and not 3=k*(0.05)?

That's just the way a spring constant is defined. If you apply a force ##F## to both sides and it compresses by ##x##, then the constant is defined to be ##k = F/x##.

If you put one end of the spring against a wall and apply a force to the other end, then the wall will provide an equal and opposite force.

In any case, the spring constant is defined by the force at one end and the total compression (not by half the compression).
 
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Thank you! I got it now
 

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