Your students will LOVE this lab!!!! By racing a car through a track they will determine the minimum potential energy necessary for their car to make it through the loop.
This lab ties in the bulk of first semester physics in high school. Not only will your students use equations associated with potential and kinetic energy, they will also calculate centripetal force, acceleration and tangential velocity around the loop.
One of my favorite quotes from the experiment is, "I had no idea what a joule really was until I did this."