# Q value of the system

1. Sep 28, 2012

### fantexihong

1. The problem statement, all variables and given/known data
The amplitude of a driven harmonic oscillator reaches a value of 21.0 F0/k at a resonant frequency of 390Hz . What is the Q value of this system?

2. Relevant equations
w0=2*pi*f0=(k/m)^(1/2)
Q=(mvo)/b
A = (Fo/m)/ (sqrt( (wo^2-w^2)^2+(b^2*w^2)/m^2) )

3. The attempt at a solution
First I did k=mw^2, 21F0/K=21F0/mw^2. Because w0=w, so the first term of the amplitude equation is 0, so I got A=F0/mbw, then I substitute Q in, I got A=QFo/mw^2. So 21F0/mw^2=QF0/mw^2. Q=21. But this is not the answer, could anybody help me please?

Last edited: Sep 28, 2012