Check out our flashlets (but they're not mobile friendly -- we're currently updating them).
This applet describes a single atom gas moving in one dimension. It accelerates or decelerates only through classical collisions with the moving piston on its container. This alone is enough to explain why the gas gets warm when it is compressed and cool when expanded.
This applet shows how atomic velocities cause the Brownian Motion of a dust particle. In one panel a small ball jitters. In the next, we see that it jitters because many smaller balls bat it rapidly about. Here's the original Java version.
A short movie of the Moon entering the Earth's shadow, and how it appears from Earth. The ancient Greeks used this picture to estimate the distance to the Moon. Their estimate was within ten per cent of the correct answer.
Prove Pythagoras' theorem by moving the triangles around--in the original configuration, the total area inside the red square is equal to that of the four identical triangles plus the area of the central square on the hypotenuse (side = triangle's longest side). Rearrange to see that the total area inside the red square is also that of the four triangles plus the sum of the areas of squares on the other two sides.
A wave pulse traveling down a uniform string under tension comes to a join with a string of different density. The pulse is partially transmitted, partially reflected. The relative densities of the two strings can be set by the slider. Note the phase of the reflected wave as a function of relative string densities. The physics is the same for a wide variety of wave reflection phenomena.
(Trial version of this.)
Old Java applet nicely illustrates motion in a two dimensional collision in the center of mass frame and the "lab" frame.
This is still in Java: Newton's imaginary cannon is on a high mountain, and fires a cannonball above the atmosphere. Depending on speed,it could fall, circle the earth, or fly away depending on how hard it was fired, showing the motion of an cannonball near the Earth and of the Moon are different aspects of the same thing. (Here's the Flash version.)
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