BallBounceHD App for iPad
'Using the BallBounceHD app, you can place between 1 and 100 balls on the screen and watch them as they move around, bouncing off the sides and colliding with one another. You can set the temperature, which controls how fast the balls move. You can also set the size of the balls, and decide whether or not they collide with one another. There are also settings to control the colors of the balls.
Compared to the iPhone version, in the iPad version there are more balls (100 vs. 50), the balls are in a larger space, and the menu to control all the settings is on the same screen that shows the balls.
With this app, you can investigate the ideal gas law, examine color mixing, Brownian motion, phase transitions, and elastic collisions.'
This app costs $0.99