Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

PLEASE REQUEST DEMOS WELL IN ADVANCE

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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Harmonic Motion: video - Pendula, Spring and Simple; Pendula, Conical and Torsional; video - Pendula, Physical (Center of Percussion); Projected Uniform Circular Motion; Damped Mass on Spring; video - Forced Oscillations; Hacksaw Blade Resonance; video - Resonance Wire Ring; video - Inverted Pendulum - Function Generator; Inverted Pendulum - Reciprocating Saw; Coupled Pendulum Oscillators; Coupled Magnetic Oscillations; Coupled Harmonic Oscillators; Lissajous Figures on the Scope; Lissajous Fifures with Laser; Parametric Amplifier / Oscillator
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video - Pendula, Physical (Center of Percussion)

Purpose:

To demonstrate the behaviour of physical pendula with regularly or irregularly distributed mass.

Procedure:

DEMO VIDEO DOWNLOAD w/ sound

The demo includes a meter stick on a pivot as well as (or) a baseball bat on a pivot. A baseball bat can be used to demonstrate the center of percussion (COP) being different from the center of mass (COM) phenomenon.

The center of percussion is the point at which, when hit at right angle to stick/bat, the rotational and translational motions of the stick/bat at it's pivot is perfectly cancelled out and one gets little to no motion at the pivot (location where one holds the bat).

One has to be careful, the center of percussion is not always defined as the "sweet spot". For example, "sweet spot" can be the point one hits to minimize "sting" or motion at the pivot, or it can be defined as the point to maximize energy transfer to the ball. These are two different things.

Hints:

Reference: What is the COP (Center-of-Percussion) and does it matter?