Solving Simple Pendulum Homework: Find the Amplitude & Phase Angle

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SUMMARY

The discussion focuses on solving a simple pendulum problem involving a 2.00-kg block attached to a spring with a force constant of 300 N/m. The initial conditions specify that the block is moving at 12.0 m/s in the negative direction at t=0, with the spring neither stretched nor compressed. The angular frequency (ω) is calculated as 12.25 rad/s. The participants explore the relationship between amplitude (A) and phase angle (φ) using the equations of motion, ultimately concluding that assuming A is non-zero leads to φ being π/2 radians.

PREREQUISITES
  • Understanding of harmonic motion equations, specifically x=A*cos(ωt+φ) and v=-ωA*sin(ωt+φ).
  • Knowledge of angular frequency calculation using ω = √(k/m).
  • Familiarity with the concepts of amplitude and phase angle in oscillatory systems.
  • Basic algebra skills to solve equations with multiple unknowns.
NEXT STEPS
  • Study the derivation and applications of the equations of motion for harmonic oscillators.
  • Learn about the physical significance of amplitude and phase angle in oscillatory systems.
  • Explore advanced topics in oscillatory motion, such as damping and resonance.
  • Investigate numerical methods for solving systems with multiple unknowns in physics problems.
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and oscillatory motion, as well as educators looking for examples of solving harmonic motion problems.

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Homework Statement


A 2.00-kg frictionless block is attached to an ideal spring with force constant 300 N/m. At t=0 the spring is neither stretched nor compressed and the block is moving in the negative direction at 12.0 m/s. Find the amplitude and the phase angle.


Homework Equations


x=A*cos(ωt+φ)
v=-ωA*sin(ωt+φ)
[tex]\omega = \sqrt{\frac{k}{m}}[/tex]

The Attempt at a Solution



[tex]\omega = \sqrt{\frac{300}{2.00}} = 12.25[/tex]
[tex]0 = A\cdot cos(\phi)[/tex]
[tex]12.0 = -12.25 \cdot A \cdot sin(\phi)[/tex]

How do I solve for something when there are two unknowns (phi and A)?
 
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Do I assume that A is non-zero, therefore making φ = Pi/2 radians?
 

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