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Phase constant of SHM

by 1MileCrash
Tags: constant, phase
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1MileCrash
#1
Oct26-11, 02:21 PM
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1. The problem statement, all variables and given/known data

The displacement of a mass oscillating on a spring is given by x(t) = xmcos(ωt + ). If the initial displacement is zero and the initial velocity is in the negative x direction, then the phase constant is:

2. Relevant equations



3. The attempt at a solution

How do I start? The book just tells me that the phase constant depends on displacement and velocity when t = 0, but doesn't say how.
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gneill
#2
Oct26-11, 03:28 PM
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Sketch a cosine curve. What's its initial value? Where on the curve would match the initial condition of the spring and mass? What's (angular) the offset from zero?
1MileCrash
#3
Oct26-11, 04:44 PM
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Quote Quote by gneill View Post
Sketch a cosine curve.
OK

What's its initial value?
1

Where on the curve would match the initial condition of the spring and mass?
Huh??

gneill
#4
Oct26-11, 04:57 PM
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Phase constant of SHM

Does the mass start at a maximum extension like the cosine function does?
1MileCrash
#5
Oct26-11, 05:04 PM
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No, initial displacement is 0. So, I need to find where cosx equals 0?
gneill
#6
Oct26-11, 05:13 PM
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Quote Quote by 1MileCrash View Post
No, initial displacement is 0. So, I need to find where cosx equals 0?
Not only that, but where it's going through zero and going negative, just like the mass' displacement.
1MileCrash
#7
Nov9-11, 06:19 PM
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Still have no clue on this.
gneill
#8
Nov9-11, 07:17 PM
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Have a gander:

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Fig2.jpg  


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