Simple Harmonic Motion with Linear Momentum

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Homework Help Overview

The discussion revolves around a problem related to simple harmonic motion and linear momentum, specifically focusing on the effects of removing half of a mass in a system undergoing oscillation. Participants are examining the relationships between period, amplitude, and momentum conservation in this context.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to derive relationships between the period and amplitude before and after a mass is removed, while others question the conservation of momentum in the scenario presented. There is a focus on how the removal of half the mass affects momentum transfer and the implications for the equations used.

Discussion Status

The discussion is active, with participants exploring different interpretations of momentum conservation and its implications for the problem. Some guidance is offered regarding considering the momenta of the two halves of the block before and after separation, but no consensus has been reached on how to adjust the momentum equation.

Contextual Notes

Participants are grappling with the implications of removing half of the mass and how it affects the conservation of momentum, with some uncertainty about the scenario's details and the assumptions being made.

lc99
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Homework Statement


upload_2018-3-27_11-35-22.png


Homework Equations


T = 2pi * sqrt(m/k)
mv =m2v2 (LM)[/B]

The Attempt at a Solution


[/B]
So T2 depends on the mass and not velocity. So i can find T2 = 2pi * sqrt([m/2]/k)

For A2 , i know that the amplitude before any collision is 1/2m1v1^2 = 1/2kA1^2
so solving that, i get v1 = A1 sqrt(k/m) .

I know that linear moment is conserved so i can find v2...
m1v1=m2v2 --> mv1 = m/2 * v2 --> v2 = 2v1 = 2A1sqrt(k/m)

With the new velocity, v2, i writing with energy conservation...

1/2mv2^2 = 1/2kA2^2, so i can find A2 in terms of v2... and substituting v2 in terms of A1 from above
solving for A2, i would get A2 = mv2^2 / k = A2^2 --> A2 = sqrt(2A1)


did i do this correctly?
 

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lc99 said:
I know that linear moment is conserved
That would mean transfer of momentum from the half mass removed to the half mass continuing. I don't read that in the scenario...
 
BvU said:
That would mean transfer of momentum from the half mass removed to the half mass continuing. I don't read that in the scenario...
so linear momentum isn't conserved?
 
Half the block is taken away, momentum included.
 
BvU said:
Half the block is taken away, momentum included.
I'm not sure what should be changed? How would i change my momentum equation?
 
lc99 said:
I'm not sure what should be changed? How would i change my momentum equation?
Consider the two halves of the block before and after separation. Before, each has momentum. If the separation does not involve any forces on them, what happens to each of the two momenta?
 

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