Ping Pong Paddle and Ball
 Tilted Air Track and Gliders.

 

Code Number: 4B70.60

Demo Title: Adiabatic Invariant

Condition: Good

Principle: Adiabatic Invariant

Area of Study: Thermodynamics

Equipment: Ping Pong Paddle and Ball, Tilted Air Track and Gliders.

Procedure:

Bounce the Ping Pong ball between the paddle and the table.  As you make the table to paddle distance smaller, the frequency of the bounce goes up even though the velocity of the ball remains relatively constant.  

Tilt the air track slightly so that the cart bounces well off the bottom stop.  Place a rubber band across the towers to use as the upper stop.  Start the cart at the upper end by the towers and let it slide down and bounce off the bottom stop.  As it bounce back, decrease the distance that the cart can bounce back by sliding the upper towers closer to the bottom stop, thus increasing the frequency of the cart bouncing between the two stops.

References:

  • Don S. Lemons, William R. Shanahan, "Adiabatic Invariance and Its Application to Wien's Complete Displacement Law of Blackbody Radiation", AJP, Vol. 92, #2, Feb. 2024, p. 132.
  • M. G. Calkin, "Adiabatic Invariants for Varying Mass", AJP, Vol. 45, #3, Mar. 1977, p. 301.
4B70.60 - Adiabatic Invariant