An 
-particle is emitted from a radioactive source with kinetic energy of 
. The -particle travels in a vacuum directly towards a gold (
) nucleus, as illustrated in the figure below.
The -particle and the gold nucleus may be considered to be point charges in an isolated system.
Explain why, as the -particle approaches the gold nucleus, it comes to rest.
For the closest approach of the -particle to the gold nucleus, determine their separation,
.
