Today I was off campus writing the curriculum for our new NGSS-aligned physics course. While I was gone, students whiteboarded three very engaging problems from Knight’s College Physics text. One (Chapter 30; Problem 33) was how radioactive iodine from the Chernobyl accident was ingested by cows and contaminated the milk. Farmers couldn’t see the milk and used it to make cheese. The problem is to solve for how long it takes for the concentration of radioactive iodine isotope to fall to 1% of its original concentration. The second problem was a typic Carbon-14 dating problem, but still interesting for students to work through. The third problem (Chapter 30; Problem 65) had students solve for how long ago the supernova occurred that produced the very heavy atoms found in the earth based on their current concentrations of uranium isotopes. Great problems!