The 2.5-kg wieght is released from rest -- Determine the spring constant k

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Homework Help Overview

The problem involves a 2.5-kg weight released from rest, with two springs of stiffness k. The objective is to determine the largest value of k for which the weight reaches a specified position B from position A, where the springs are undeformed.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the gravitational potential energy at different positions and question the appropriate values to use for calculations. There is also a focus on understanding the concept of potential energy and its reference point.

Discussion Status

The discussion is active, with participants providing feedback on each other's reasoning and questioning assumptions about potential energy. Some guidance has been offered regarding the conservation of mechanical energy, but there is no explicit consensus on the interpretation of the problem or the values to use.

Contextual Notes

Participants are navigating the definitions of weight and potential energy in relation to the problem setup. There is also a mention of the appropriateness of the forum for posting questions from a specific textbook.

Alexanddros81
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Homework Statement


14.27 The 2.5-kg weight is released from rest in position A, where the two springs
of stiffness k each are undeformed. Determine the largest k for which the weight
would reach position B

Fig P14_27.jpg


Homework Equations

The Attempt at a Solution



Pytels_Dynamics115.jpg


Hi. Can you check if I am going at the right direction?
Also for ##Wy_B## and ##Wy_A## am I replacing with 2.5(0.45) and 2.5(0.3) respectively?
 

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So far so good except for the gravitational potential energy.
 
Do I replace ##Wy_A## and ##Wy_B## with 2.5(0.3) and 2.5(0.45) respectively?
 
Alexanddros81 said:
Do I replace ##Wy_A## and ##Wy_B## with 2.5(0.3) and 2.5(0.45) respectively?
Almost but not quite. Something is missing. The problem talks about a 2.5-kg weight. Is weight measured in kilograms?
 
A yes but ofcourse W = mg where mass is m=2.5kg.
But I don't understant why the Potential Energy of W is mg(0.3) at position A and mg(0.45) at position B.
I mean I don't understant it in relation to the Figure.
Can you explain to me a bit more?
At Which point do I say that the potential energy of W is zero? (in the figure)
 
Last edited:
Alexanddros81 said:
At Which point do I say that the potential energy of W is zero? (in the figure)
Any point you like. The zero of potential energy is irrelevant. Consider this, when a mass moves from point A to B, mechanical energy conservation says
TA + UA = TB + UB
or
TB - TA + UB - UA = 0
or
ΔT + ΔU = 0.
It's the difference that matters, not where you put the zero of energy because it drops out.
 
By the way do I post problem questions from
'Orbital Mechanics for Engineering Students' by Curtis
in this forum (Introductory Physics Homework)?
 
Last edited:
Alexanddros81 said:
By the way do I post problem questions form Orbital Mechanics for Engineers by Curtis
in this forum (Introductory Physics Homework)?
I am not familiar with the textbook. I looked at its table of contents and I think "Advanced Physics Homework" would be more appropriate. Try that and if I am wrong, a mentor will move it to its rightful place, perhaps in "Engineering."
 
Ok so here is my solution:

Pytels_Dynamics118.jpg
 

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I didn't run the numbers, but the method is correct.
 
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