Interrupted Pendulum

A pendulum swings from a support post and another post is added to interrupt its swing. We desire to know the maximum height at which the pendulum will perform a full loop around the post. The pendulum requires both potential and kinetic energy in order to complete a full loop. Therefore, it will never be able to return to its height of release while completing a full loop. Ultimately, the pendulum has enough energy to complete a full loop when interrupted at a height equal to two-fifths its initial height of release.

 

Dartmouth professor discusses Foucault's pendulum

Physics and astronomy professor Jim LaBelle discusses the science behind a classic physics experiment, Foucault's pendulum, while seated next to Dartmouth's pendulum in Fairchild Tower.

 

Hewitt-Drew-it! 29. Potential and Kinetic Energy

Paul derives kinetic energy from Newton's second law, and illustrates energy transfers for a block of sliding ice.

Other Hewitt-Drew-it! videos

Inverted Pendulum

A physical pendulum finds stability in its inverted position when driven at the proper frequency and amplitude combination.

The physical pendulum seen here is mounted on a ball-bearing pivot and can rotate 360 degrees; the pivot is driven at about 50 Hz with an amplitude of about 1 cm (3/4" per stroke) by a Sears Craftsman Auto Scroller Saw (model 315.172090); the length is 45 cm and the center of mass is slightly above 15 cm from the pivot; the rotational inertia is roughly 4x10^(-4) kg*m^2; the mass is about 100 grams.

For more details and references for further study see: http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa... 

 Shot in 24 and 300 fps. Thanks to Rob, Fu, and Daniel for their help.

    

Science off the Sphere: Spring Theory

How do you measure mass in a weightless environment? NASA Astronaut Don Pettit demonstrates as part of a collaboration between NASA and the American Physical Society.

Other Science off the Sphere videos

Vortex Shedding (Flow Tank Version)

Wolfgang uses a pendulum partially immersed in a makeshift flow tank to show us the effect of vortex shedding on a small object.


When fluid flows around a cylindrical object, there is a range of flow velocities for which a von Karman vortex street is formed. The shedding of these vortices imparts a small, periodic force on the object. Here the object is a cylinder attached to a physical pendulum whose frequency of oscillation is adjustable. The end of the cylinder is submerged in flowing water. When the frequency of the pendulum is adjusted to match the frequency of vortex shedding, the cylinder swings transverse to the direction of flow with a peak-to-peak amplitude of a few centimeters.

Other Harvard demonstrations

The Pendulum and Galileo

Galileo's investigation of the pendulum played a role in the evolution of science. He performed some of the first experiments while discovering the relationship among length, mass and displacement. If you are teaching the scientific method, the pendulum is a good project to start with. Galileo probably gained insight into many issues around motion from his investigation of the pendulum. The video also mentions issues with the church and academia.