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:
Measurement
Motion In One Dimension
Motion In Two Dimensions
Newton's First Law
Newton's Second Law
Newton's Third Law
Statics Of Rigid Bodies
video  - Center of Mass of Virginia
video  - Center of Mass Toys
Stacking Blocks
video  - Stability Track
photos  - Tension in a String
Rope and Three Students
photos  - Knot in Static Equilibrium
Force and Tension
The Roman Arch
Rotational Equilibrium
video  - Giant Yo-Yo
Applications Of Newton's Laws
Gravity
Work and Energy
Momentum
Rotational Motion
Properties of Matter

### video  - Center of Mass Toys

#### Purpose:

To illustrate the concept of center of mass.

#### Procedure:

Various aspects of center of mass can be demonstrated through creative use of the toys (pictured below).

1. Balancing Spoon & Fork with Match Stick: can be used with a cup
2. Tiltable Prism: with plumb bob falling within area of its base, the prism stands; if not, the prism falls
3. Tightrope Mickey Mouse: with long downward bending pole with masses on either end lowers Mickey's center of mass to below the rope establishing a stable equilibrium in addition to increasing his moment of inertia
4. Double Cone rolling up the incline: seems to roll uphill, but actually rolls toward diverging rails
5. Balancing Horse: with the center of mass below its feet
6. Leaning Tower of Pisa: is unstable with top in place and stable with top removed
7. Semi Circle with adjustable ball mass: system stable with ball at bottom of support rod
8. Balancing Bird: with the center of mass at the tip of its beak

#### Hints:

Try balancing a soda can at 45-deg angle that is full, partially full and empty. You'll find that a stable equilibrium is achieved with a can about 1/3 full.

#### Equipment:

• Center of Mass Toys