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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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 Motion In One Dimension
 Motion In Two Dimensions
 Newton's First Law
 Newton's Second Law
 Newton's Third Law
 Statics Of Rigid Bodies
 Applications Of Newton's Laws
 Brachistochrone curve
 Cavendish Balance Model
 Gravitational field model
 Work and Energy
 Rotational Motion
 Properties of Matter

Cavendish Balance Model


A show-and-tell version of the famous Cavendish experiment.


The laser is reflected off the mirror in the apparatus onto a screen across the room. Shifting the large masses (very gently) to the opposite side of the setup should cause a slight deflection of the beam after some time but the setup is far too sensitive to vibrations to get any real quantitative results in the classroom. This is more of a "show-and-tell" demo.

Although we have the Leybold version of the balance, here is a link to the PASCO version as a reference.


The torsional pendulum is usually fastened in place to remain stationary during storage and transport. Once set up in place in the classroom, loosen the screws (one under each small mass) to allow the pendulum to hang free


  • Laser
  • laser stand
  • Cavendish Balance Apparatus