Torsional pendulum, logarithmic decrement

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SUMMARY

The discussion focuses on calculating the level of damping in a torsional pendulum using the logarithmic decrement. The amplitude of the torsional vibration decreases to 13% of its original value after 100 cycles. The correct formula to use is ln(100/13), which results in a logarithmic decrement of approximately 2.04. This calculation confirms that the damping is positive, reflecting the decay in amplitude over the specified cycles.

PREREQUISITES
  • Understanding of torsional pendulum dynamics
  • Familiarity with logarithmic decrement calculations
  • Basic knowledge of amplitude and damping concepts
  • Proficiency in natural logarithm functions
NEXT STEPS
  • Study the principles of torsional vibrations in mechanical systems
  • Learn about the derivation and applications of logarithmic decrement
  • Explore damping ratios and their significance in oscillatory motion
  • Investigate the effects of different damping mechanisms on vibration amplitude
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Students in physics or engineering, particularly those studying mechanical vibrations, as well as educators teaching concepts related to damping and oscillatory motion.

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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?
 
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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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