Physics
Physics
Problem
1. a Estimate the nuclear radii of an alpha particle and a nucleus of platinum ( ). 2. b Determine the initial energy of an alpha particle directed towards the platinum nucleus such that the alpha particle stops just as the nuclear surfaces touch.Intuitive explanation
The nuclear radius follows a simple scaling law based on mass number—heavier nuclei are larger, but not by much. Once you know both radii, you can use energy conservation: all the alpha particle's initial kinetic energy converts to electric potential energy when the two nuclei just touch, since they repel each other electrostatically. The key is recognizing that "stops just as surfaces touch" means the separation distance equals the sum of the two radii.
Intuitive explanation
The nuclear radius follows a simple scaling law based on mass number—heavier nuclei are larger, but not by much. Once you know both radii, you can use energy conservation: all the alpha particle's initial kinetic energy converts to electric potential energy when the two nuclei just touch, since they repel each other electrostatically. The key is recognizing that "stops just as surfaces touch" means the separation distance equals the sum of the two radii.