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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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 Surface Tension
 Fluid Statics
 Fluid Dynamics
  video  - Torricelli's Law
 Air Driven Devices
  video  - Venturi Tube
 Toilet paper gun
  video  - Airplane Wing in Wind Tunnel
  video  - Air Flow Dynamics
 Magnus Effect - Cart on Track
  video  - Magnus Effect Appartus
 Terminal Velocity in Glycerin and Water
 Terminal Velocity of Coffee Filters
  video  - Laminar and Turbulent Flow
 Tornado Vortex
 Vortex Cannon

 video  - Venturi Tube


Qualitative verification of Bernouilli's equation - demonstrate the operation of a Venturi tube and verify the variation of gas velocity with cross sectional area of the tube.


centered image


Connect the Venturi tube's hose to a compressed air source and show different pressures in flow tube by flowing air through system and noting pressure relationships by the level of colored liquid in the tubes.


First Image: Place a white background between tubes and stand to allow for a better uncluttered view of the setup. The "large setup" glass has been cleaned out (remove dark ink) and replaced with fresh blue food colored water as of Summer 2014.

Second Image: Note: the large cross section pipes after the narrowing almost never show the same level as the first large pipe due to pressure drop across the length of tube. The last two U-tubes would show different heights (showing this pressure drop with length) if one made the tube extremely long and separate the U-tubes further. There are also effects due to the fluid's friction with tube surface.

Third Image: We have an alternative setup with only 3 tubes available. It might be a bit difficult to see in Rm. 203, but the advantage is that the flow velocity could be controlled with the pump.


  • Compressed Air Source
  • Venturi Tube