This is a great pre-assessment for a simple machines unit. Student's are to design a device that will lift an elephant out of it's cage. You can use this to preasses what machines students already know by what they use in their drawings (lever, incline plane, pulley, ect.). At the end of your unit, give this same assignment to students again and see how their drawings are different. This also works great to show students their first drawings and have them reflect on what they have learned about simple machines and how they make work easier.