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Simple pendulums

  • Thread starter cdotter
  • Start date
305
0
1. The problem statement, all variables and given/known data
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.


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

3. 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)?
 
305
0
Do I assume that A is non-zero, therefore making φ = Pi/2 radians?
 

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