- #1
Teclis
- 25
- 2
- Homework Statement
- This is problem 21 b) from Section 8.1 of Marsden and Weinstein Calculus II
A mass of 1 kg is hanging from a spring. If x = 0 is the equilibrium position, and x = 1 and x' = 1 when t = 0. The wave is observed to oscillate with a frequency of twice a second. What is the amplitude of the wave?
- Relevant Equations
- x = Acos(wt) + Bsin(wt)
Using A = x0, B = v0/ω
I get
ω = 4π, A = 1, B = 1/4π
then converting to phase/magnitude form
[itex] \sqrt{A^{2} + B^{^{2}}} = \alpha [/itex]
[itex]\sqrt{1^{2} + \left ( \frac{1}{4\pi }\right )^{^{2}}} = \alpha = \frac{1}{4\pi }\sqrt{16\pi^{2} +1}[/itex]
However the answer in the back of the book has
α = 1
Is the answer in the back of the book incorrect? If the books answer is correct, could someone please point out my mistake?
I get
ω = 4π, A = 1, B = 1/4π
then converting to phase/magnitude form
[itex] \sqrt{A^{2} + B^{^{2}}} = \alpha [/itex]
[itex]\sqrt{1^{2} + \left ( \frac{1}{4\pi }\right )^{^{2}}} = \alpha = \frac{1}{4\pi }\sqrt{16\pi^{2} +1}[/itex]
However the answer in the back of the book has
α = 1
Is the answer in the back of the book incorrect? If the books answer is correct, could someone please point out my mistake?