Technical data

Forced oscillations - Pohl's pendulum with measure Dynamics

Article no: P2132785

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Principle

If an oscillating system is allowed to oscillate freely, we can observe that the decrement of successive maximum amplitudes strongly depends on the damping value. If the oscillating system is caused to oscillate by an external torsional oscillation, we can observe that the amplitude in a stationary state is a function of the frequency and amplitude of the external periodic torsional oscillation and of the damping value. The aim of this experiment is to determine the characteristic frequency of the free oscillation as well as the resonance curve of a forced oscillation.

Benefits

Long-lasting oscillation due to ball bearings
Damping via abrasion-resistant eddy current brake
Simple illustration of the elementary principle of forced oscillations
Suitable for demonstration and student experiments as well
Easy measurement and evaluation via movement tracking software

Tasks

A. Free oscillation

Determination of the period of oscillation and characteristic frequency for the undamped case.
Determination of the period of oscillation and corresponding characteristic frequencies for various damping values. Calculation of the corresponding ratios of damping, damping constant, and logarithmic decrement.
Realisation of the aperiodic case and creeping case.

B. Forced oscillation

Determination of the resonance curve and graphical representation of the resonance curve by way of the damping values of A.
Observation of the phase difference between the torsional pendulum and the exciting, external rotation for a small damping value with different excitation frequencies.

Learning objectives

Angular velocity
characteristic frequency
resonance frequency
torsional pendulum
torsional oscillation
restoring torque
damped/undamped free oscillation
forced oscillation
ratio of damping/decrement
constant damping
logarithmic decrement
aperiodic case
creeping

Scope of delivery

Torsion pendulum after Pohl	11214-00	1
Connecting cable, 32 A, red, various lengths	07362-01	2
Connecting cable, 32 A, blue, various lengths	07362-04	2
Software "Measure Dynamics", single user	14440-61	1