Simple Harmonic Motion: What is Phase Constant?

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Discussion Overview

The discussion revolves around the concept of the phase constant in Simple Harmonic Motion (SHM), specifically its role and implications in the mathematical representation of SHM. Participants explore whether the phase constant represents the initial position of the particle and how it affects the graph of motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the phase constant \(\phi\) is equivalent to the initial position of the particle in SHM.
  • Another participant asserts that the phase constant represents the initial angle or phase at time \(t = 0\).
  • A participant suggests that if the phase constant is omitted, the motion is merely shifted in phase but retains the same key features.
  • Concerns are raised about how different values of \(\phi\) would affect the starting points of the sinusoidal graph for the same amplitude and frequency.
  • One participant proposes that by adjusting the starting time, the phase constant can be effectively eliminated, leading to a phase constant of zero.
  • There is confusion expressed by one participant regarding the implications of eliminating the phase constant and its relationship to the initial angle.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the phase constant, with some agreeing on its role as the initial angle while others question its implications on the graph of motion. The discussion remains unresolved regarding the exact nature and impact of the phase constant.

Contextual Notes

Participants have not fully clarified the assumptions regarding the definitions of phase constant and initial position, nor have they resolved the mathematical implications of eliminating the phase constant.

justwild
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I just started learning Simple Harmonic Motion and encountered a word Phase Constant [itex]\phi[/itex] .
Actually it appeared as
f(t)=rsin([itex]\omega t+\phi[/itex])
I am confused whether phase constant is actually the initial position of the particle(which execute SHM) and therefore the point on graph at time=0 or not!
 
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welcome to pf!

hi justwild! welcome to pf! :wink:

you're right, the phase constant is the initial angle (or initial phase): the angle (or phase) at t = 0 :smile:
 
what is the harm if we just take [itex]\omega t[/itex] as the argument.
 
You just shift the motion in phase slightly. All te same key features are there.
 
If [itex]\phi[/itex] is the initial angle then I think the sinusoidal graph will show different starting points(t=0) for different values of [itex]\phi[/itex] of the same amplitude and frequency of vibration. Is that so?
 
justwild said:
what is the harm if we just take [itex]\omega t[/itex] as the argument.

you can eliminate the phase constant by changing the starting time …

if you replace t by t + φ/ω, then the phase constant is zero :smile:
justwild said:
If [itex]\phi[/itex] is the initial angle then I think the sinusoidal graph will show different starting points(t=0) for different values of [itex]\phi[/itex] of the same amplitude and frequency of vibration. Is that so?

not following you :confused:
 

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