Wrapping up our Simple Machines unit, second graders partnered with their fifth grade buddies to build a z-pulley on the playground! First, students tried lifting a fifth grader off the ground with only one pulley. Even with all their strength, the fifth grader did not budge off the ground. By creating a z-pulley, with two pulleys and two Prusik knots, students discovered that you can use less force if that force is extended over a longer distance. It was a great opportunity for students to learn, firsthand, how z-pulleys are used in crevasse rescue situations to make work easier.