Find Unknown Weight w/ Ideal Spring Problem

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Homework Help Overview

The problem involves an ideal spring and a scale, where different weights produce varying readings on the scale. The original poster attempts to determine the spring constant and the unknown weight based on the readings provided for known weights.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of the spring constant, noting inconsistencies in the values obtained for different weights. There is an exploration of the relationship between the weights and the scale readings, with attempts to derive a constant weight affecting the scale.

Discussion Status

Some participants have offered hints regarding the missing information about the scale's reading with no weight attached. One participant has proposed a method to solve for a constant weight, leading to a scale reading that aligns with expectations. However, there is no explicit consensus on the best approach or whether alternative methods exist.

Contextual Notes

Participants are working under the assumption that the spring constant should be consistent, and they are questioning the implications of the scale's readings with varying weights. The lack of information about the scale's reading without any weight is noted as a potential factor in their calculations.

Potatochip911
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Homework Statement


An ideal spring hangs next to a scale, when a 100N weight the scale reads 40, when a 200N weight is attached it reads 60. Using an unknown weight reads 30.

Homework Equations


F=-kx

The Attempt at a Solution


I attempted to find the value of k for the spring however when calculating k for the 100N it is 2.5N/m and for the 200N it is 3.3N/m which doesn't make sense to me since I would've thought k would be constant. I also tried using F/x=F/x but this also didn't work so I'm completely lost.
 
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Potatochip911 said:

Homework Statement


An ideal spring hangs next to a scale, when a 100N weight the scale reads 40, when a 200N weight is attached it reads 60. Using an unknown weight reads 30.

Homework Equations


F=-kx

The Attempt at a Solution


I attempted to find the value of k for the spring however when calculating k for the 100N it is 2.5N/m and for the 200N it is 3.3N/m which doesn't make sense to me since I would've thought k would be constant. I also tried using F/x=F/x but this also didn't work so I'm completely lost.
Hint: you are not told what the scale reads when no weight is attached.
 
haruspex said:
Hint: you are not told what the scale reads when no weight is attached.
Thanks! I solved for the constant weight that is being applied to the scale.
(100+c)/40=(200+c)/60
This gave c=100
Including this constant weight in the equations gave the correct scale reading of 50.
I'm assuming this is how you would solve it because it produced the correct answer although there might be a different way.
 
Potatochip911 said:
Thanks! I solved for the constant weight that is being applied to the scale.
(100+c)/40=(200+c)/60
This gave c=100
Including this constant weight in the equations gave the correct scale reading of 50.
I'm assuming this is how you would solve it because it produced the correct answer although there might be a different way.
That's as good a way as any.
 

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