3A10.40 • Pendula: Mass-Period Independence
Location: Cabinet 5
Concepts Conveyed:
- The frequency of a pendulum in simple harmonic motion depends only on the pendulum's length, not mass.
- Even with light damping, pendulums with different-mass bobs should have the same frequency for their first few oscillations.
- The pendulums can be released at different angles from one another since the angle of release is also independent of the frequency in the small-angle approximation (sin(θ)≅θ in the equation of motion).
- Light damping is seen with this demo, particularly affecting the amplitude of the foam-bob pendulum.
Instructions / Notes:
- The masses of the bobs were measured to be 229.21 ± 0.10 g (steel), 35.26 ± 0.05 g (wood), and 2.59 ± 0.05 g (foam).
- The lengths of the pendulums from the bottom of the cross bar to the center of the balls were measured to be 38.58 ± 0.09 cm (steel), 38.65 ± 0.05 cm (wood), and 38.7 ± 0.1 cm (foam).
- Use the initiator stick to displace the pendula, then remove quickly.
- Observe the initial oscillations of the pendulums.
Demo Staff:
- Be sure to have the initiator stick with the pendulums.
Last updated on April 8, 2025