Torsional pendulum, logarithmic decrement

tone999

1. The problem statement, all variables and given/known data

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.

2. Relevant equations



3. The attempt at a solution

Is this simply ln(100/13)= 2.04

or ln(13/100)= -2.04?

Redbelly98

It will be a positive number (use 100/13, not 13/100). However, you still need to account for the fact that it takes 100 cycles to reach 13%.