Neutrons produced in the fission of uranium are rapidly moving projectiles and must be slowed before they can produce more fission.If the neutrons collide elastically,hydrogen is effective in slowing them down because
A)hydrogen atoms repel neutrons.
B)a hydrogen atom is much more massive than a neutron.
C)a hydrogen atom and a neutron have about the same mass.
D)a neutron is much more massive than a hydrogen atom.
E)hydrogen atoms attract neutrons.

Question

Quizplus · Accepted Answer

A neutron and a hydrogen atom have about the same mass, making elastic collisions between the two effective in slowing down the neutrons. This is known as neutron moderation. Hydrogen is commonly used in nuclear reactors as a moderator to slow down the neutrons and increase the chance of further fission reactions.

Neutrons Produced in the Fission of Uranium Are Rapidly Moving