# Torsional Pendulum, Logarithmic Decrement

1. Jul 21, 2009

### tone999

The amplitude of a torsional vibration decreases so that the amplitude on the 100th cycle is 13% of the the amplitude of the first cycle. Determine the level of damping in terms of the logarithmic decrement.

Is this simply ln(100/13)= 2.04

or ln(13/100)= -2.04?

2. Jul 22, 2009

### rl.bhat

Level of damping δ = 1/n*ln(xo/xn)
where n is the number of cycles, xo is the initial amplitude and xn is the amplitude after n cycles.