# Calculating Qfactor

1. Sep 4, 2009

### Eric_meyers

1. The problem statement, all variables and given/known data
"Systems typically exhibit an exponential decrease in their average stored energy of the form <E> = E$$_{0}$$ e^(-vt) ---- If a piano key of frequency 256 Hz is struck and its oscillation energy decreases to one half of its initial value in about 1 second what is the effective Qf of the system?

2. Relevant equations

Qf = w/v
<E> = E$$_{0}$$ e^(-vt)

3. The attempt at a solution

I need to find the energy dissipated and from the equation they gave me I put 1/2 (the energy the system has from its initial value after 1 second)

1/2 = e^(-v)

v = .693

Qf = 256/.693 = 369

I'm not quite sure if I did the dissipation energy equation correctly.

2. Sep 4, 2009

### Winzer

$$Q=\frac{\omega}{v}=\frac{2 \pi f}{v}$$. Your numerator needs to be in angular frequency. Looks fine though.