Goldilocks and the three bears
Yesterday I was going through moderation of neutrons in fission reactors with my HL students. I wanted them to consider what makes a good moderator, so got talking about collisions between a small particle and a big one.
So which would take most energy from Goldilocks, a big daddy bear a medium sized mummy bear (about the same size as goldilocks herself) or a small baby bear? To find out goldilocks ran into the three bears. Daddy bear was far too big and Goldilocks bounced off. Baby bear was too small and bounced off Goldilocks with so much speed that he flew right through the window of the little cottage leaving Goldilocks to run into Mummy bear. She was just right, taking almost all of Goldilocks translational kinetic energy but leaving enough rotational for her to lie down and fall soundly asleep on Mummy bears feather bed.
My students worry about me sometimes.
Tags: Moderation, collisions