Rutherford scattering model: Steel balls, launcher, and "hill".

Rutherford scattering model: Steel balls, launcher, and "hill". Ref.:Modern College Physics by Harvey White, 6th ed., p. 837-841 Rutherford performed experiments bombarding thin gold foil with high-speed _ particles, demonstrating that the positive charge and mass of gold nuclei were confined to a space smaller than 10 cm in diameter. As an _ particle approaches a charged gold nucleus, it is deflected by electrostatic repulsion into a hyperbolic trajectory. The graph of the potential energy versus distance between _ particle and positively charged nucleus is hyperbolic as well. See Fig.1. If this graph is rotated about the vertical axis, an actual physical model can be constructed where the peak of the hill represents the nucleus of the atom. Steel balls representing _ particles are rolled down a ramp towards the potential hill of the nucleus. The balls approach the hill at different angles, rolling up to a certain height then veering off to one side or the other. The paths, when viewed from above, are hyperbolas, except for the case of a head-on collision where the ball rolls up to a certain point then reverses direction and rolls back. (Also, a ball may roll up the side and drop into the center of the hill, representing a capture prior to disintegration.) The potential energy of the _ particle near a nucleus is analogous to the potential energy of the ball on the hill. The electrostatic repulsion between _ particle and nucleus is analogous to the downward pull of gravity on the ball.