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Rutherford scattering

The simulation below shows an interaction between two "particles."  The interaction force is an inverse-square force; that is, the interaction force varies as 1/(r*r) where r is the distance between them.  This collision is similar to the type of collisions that occurred between alpha particles and gold nuclei in the famous Rutherford experiment.  This experiment showed that the very massive gold nuclei were very small compared to the size of the atom and that the positive charge (i.e. protons) was contained in a small space (the nucleus). In that experiment, the gold nuclei were essentially "fixed" in place. However, in the simulation below, both particles are "free". To simulate the Rutherford experiment, make the red particle's mass about 50 times the blue particle's mass. You'll see that the red particle's velocity after the collision will be very small. Vary the initial height of the alpha particle to notice that it will pass the gold nucleus with very little scattering.

are scriptable Java Applets written by Wolfgang Christian of Davison College.