How Is Spring Constant Calculated in Simple Harmonic Motion?

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Homework Help Overview

The discussion revolves around calculating the spring constant in the context of simple harmonic motion, specifically involving a fisherman's scale and a hanging weight. The original poster presents a problem that includes determining the spring constant and the amplitude and frequency of vibration when a fish is pulled down and released.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to relate potential energy and kinetic energy in the context of spring motion but expresses confusion about the necessary variables. Some participants question the application of Hooke's law and the definitions of amplitude and potential energy.

Discussion Status

Participants are actively engaging with the problem, with some providing hints and encouragement. There is a recognition of confusion regarding the concepts involved, particularly around amplitude and energy conservation. Multiple interpretations of the problem are being explored, and guidance has been offered without reaching a consensus.

Contextual Notes

The original poster indicates a lack of familiarity with the concepts, having just learned about them, which may affect their understanding of the problem. There is also mention of not knowing certain variables, such as time and potential energy, which are relevant to the discussion.

meganw
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Homework Statement



A fisherman's scale stretches 3.4 cm when a 3.3 kg fish hangs from it.

(a) What is the spring constant?

(b) What will be the amplitude and frequency of vibration if the fish is pulled down 2.5 cm more and released so that it vibrates up and down?

Homework Equations



I know that the PE of a spring is .5kA
I also know that x=Asinwt

But I don't know t, so I can't see how I'd use that equation either.

The Attempt at a Solution



I know that equation, but how can I set it equal to the KE of the spring when I don't know the velocity of the spring at all?? I thought this might be a conservation of energy problem but I don't see how that would work out.
 
Last edited:
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Have you met Hooke's law yet?
 
I got it right now, (thank you! =) But how do you find the amplitude on part b?? I don't know the PE, or time...

I'm sorry we just learned this and I'm really confused still.
 
Last edited:
meganw said:
I got it right now, (thank you! =) But how do you find the amplitude on part b?? I don't know the PE, or time...
But surely you can just see the amplitude, it's given to you in the question..:wink:
meganw said:
I'm sorry we just learned this and I'm really confused still.
Not a problem, and you don't have to apologise for asking questions, you should always ask questions :smile:
 
The amplitude of a SHM system is how far the object has been stretched from it's initial position.
 

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