[Work and Energy] Work positive or negative?

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Homework Help Overview

The discussion revolves around understanding the conditions under which the work done by a spring is considered positive or negative, focusing on the theoretical aspects of work in the context of springs.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the conditions that determine the sign of work done by a spring, questioning the relationship between spring motion and work. Some attempt to clarify the concept of work in relation to everyday experiences with springs.

Discussion Status

Participants are actively engaging with the concept, offering different perspectives on the sign convention of work done by springs. There is a mix of interpretations regarding when the work is positive or negative, but no consensus has been reached yet.

Contextual Notes

Some participants reference the need for a clear understanding of sign conventions and the implications of negative work in relation to motion, indicating potential gaps in foundational knowledge.

hiuting
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Homework Statement


I don't know when the work of a spring is negative, and when it's positive... When is the work of a spring negative and when is it positive?


Homework Equations


Wsp= -(1/2)(k)(xf2-xi2)

The Attempt at a Solution


I can get Wsp to be positive when the spring is stretch, but I want to know the theory behind it.
 
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When does a spring oppose motion?

think about it in your everyday life pushing and pulling a spring
 
It's a sign convention. When a spring is compressed, something does work on the spring. So the work done by the spring is negative.

When the spring stretches, the spring does work on the 'something', so the work done is positive.
 
but negative work means opposing motion, therefore the spring always does negative work
 

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