Since the nucleus of gold is about 50 times heavier than an
a-particle, it is reasonable to assume that it remains stationary
throughout the scattering process Under these assumptions, the
trajectory of an alpha-particle can be computed employing Newton’s
second law of motion and the Coulomb’s law for electrostatic
force of repulsion between the alpha-particle and the positively
charged nucleus FIGURE 12 3 Experimental data points (shown by
dots) on scattering of a-particles by a thin foil at
different angles obtained by Geiger and Marsden
using the setup shown in Figs