A pendulum experiment is performed inside a chamber that has been partially filled…
PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
A pendulum experiment is performed inside a chamber that has been partially filled with a light oil. The bob is completely immersed in the oil, while the string and pivot remain in air. The initial amplitude is kept below 5∘.
(i) Explain how the presence of the viscous medium affects (a) the amplitude and (b) the time period of oscillation for small damping.
(ii) Successive maximum displacements are observed to fall to 90% of the previous value. Calculate the fractional decrease in mechanical energy of the pendulum per oscillation.
(iii) After several oscillations the measured time period is found to have increased by about 2% compared with the undamped value. Provide a plausible physical explanation for this observation without invoking concepts beyond the Class 11 syllabus.