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Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography


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

 video  - Pendula, Physical (Center of Percussion)


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


centered image

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.


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