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?
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%.