Pinner wrote: This is part 2 of a 6 part hands-on unit on inventions and simple machines. Build and test catapults, lift an adult using a lever, test out screws of various threads, and more! My lessons are geared toward 3rd-4th grade level children and their siblings. These are lessons I created to do with a weekly homeschool co-op. We meet each week for 2 ½ hours and have 13 children between the ages of 1-13. Use these fun lessons with your classroom, family, or co-op!