Elastic Potential- Acceleration with springs

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Homework Help Overview

The problem involves a 1.6kg mass suspended from a spring in a stationary elevator, which then accelerates upwards, causing the spring to stretch further. The objective is to determine the elevator's acceleration based on the spring's behavior.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss using the equation of motion (Fy = may) to analyze the forces acting on the mass and the spring. There are questions about how to find the spring constant (k) and the implications of the spring's behavior before and after the elevator starts moving.

Discussion Status

Some participants have provided calculations for the spring constant and the acceleration, while others have raised questions about the accuracy of these values. There is an ongoing exploration of the relationships between the forces involved and the spring's properties.

Contextual Notes

Participants note that the spring constant (k) is not initially provided, leading to discussions about how to derive it from the given information. There is also a mention of the potential energy, though its necessity in solving the problem is questioned.

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Homework Statement


A 1.6kg mass is suspended from a spring inside a stationary elevator. The spring stretches 12cm. The elevator now accelerates upwards, and the spring extends a further 12cm. What is the elevator's acceleration?


Homework Equations


Fy= may
Ue= 1/2 (kx2)

The Attempt at a Solution


I'm just not sure on the best way to start this question.
 
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I would start with the first equation you provided. F_y = ma_y. What's the acceleration (a_y) in this problem? Where you can find a force on the system?
 
Fy=may
kx-mg=may
ay=(kx-mg)/m

but k is not given...
 
You need to find k first. What's the spring doing BEFORE the elevator starts moving?
 
Fy=may
kx-mg=0
k=(mg)/x
k=1306.666 N/m

Fy=may
kx-mg=may
ay=(kx-mg)/m
ay=9.79999 m/s2
 
I got a different value for k, could you double check it? My answer was a magnitude different.
 
oops, so k=130.666 N/m
 
Right, and you also know the distance so now would be a good time to find the potential.
 
Looks to me like you're done. No need for the potential in this problem.
 
  • #10
Ah, yep. I was hasty.
 

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