Moderating a Neutron In a nuclear reactor, neutrons released bynuclear fission must be slowed down before they can triggeradditional reactions in other nuclei. To see what sort of materialis most effective in slowing (or moderating) a neutron, calculatethe ratio of a neutron's final kinetic energy to its initialkinetic energy, Kf/Ki, for a head-on elastic collision with each ofthe following stationary target particles. (Note: The mass of aneutron is m=1.009u, where the atomic mass unit, u, is defined asfollows: 1u=1.66×10−27kg.) 1. An electron (M=5.49×10−4u). Expressyour answer using four significant figures. 2. A proton (M=1.007u).Express your answer using one significant figure. 3. The nucleus ofa lead atom (M=207.2u). Express your answer using four significantfigures.
