A Neutron in a Nuclear Reactor Makes an Elastic Head-On

Multiple Choice

A neutron in a nuclear reactor makes an elastic head-on collision with a carbon atom initially at rest.(The mass of the carbon atom is 12 times that of the neutron. ) What fraction of the neutron's kinetic energy is transferred to the carbon atom?

A) 14.4%
B) 28.4%
C) 41.4%
D) 56.6%