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.

 Choose a Topic or Enter a keyword to search: I cannot find what I want! You have selected the following Demos: None Selected

Choose a subtopic:
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
Vortex Cannon

### Terminal Velocity of Coffee Filters

#### Purpose:

A quantitative example of inertial drag

#### Procedure:

First get a suitable distance to time the falling of the filters. The top of the bench is a good reference, measure the height with a meter stick. Drop a single filter from a height at least a meter above the table so that it is travelling at terminal velocity by the time it reaches the table. Measure the time it takes for the filter to fall from the top of the table to the ground and record the measurement. You'll probably want to take a few measurements and average them. Next, drop 4 filters at once, making sure they are stacked tightly. Make the same measurements as before. the time for 1 filter to drop should be twice that for 4 filters to drop. Since the drag force was increased by a factor of four (4 filters insead of 1), and the speed only increased by a factor of 2, the drag force must be proportional to the speed squared. At least it is consistant with this, you could make more measurements with different numbers of filters to be sure.

#### Equipment:

• coffee filters
• Stop Watch