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Torsional pendulum, logarithmic decrement

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tone999
#1
Jul21-09, 06:33 PM
P: 18
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?
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Redbelly98
#2
Jul22-09, 07:48 AM
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P: 12,069
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%.


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