Torsional pendulum, logarithmic decrement

[tone999]

Homework Statement

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.

Homework Equations

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%.