You would think that it would be easy to put three simple machines in a box and move marbles from box to box.  Turns out that classes often do a good job, but the task is far harder than they expected. 

• any size box is fine, just not as big as a refrigerator box

• must incorporate three different simple machines

• students work in groups of about three

• a marble must move from box to box (or cause motion in the next box)

• can't use prefabricated materials  ie: parts from the mousetrap game

• grading is based on machines used and how well groups accept and hand off marbles

• more than one marble may be used

• a small grade is given each day for bringing in materials to possibly use (duct tape is like gold!)

For one week, class periods are spent with this format: half the period is spent doing more traditional activities, like reading, notes, worksheets, and problems, and the other half is spent preparing boxes.  On the final day, the whole period is devoted to the boxes.  I recommend that they do trial runs to perfect their mechanisms.  Sometimes classes dig in and do a great job.  Sometimes classes wait till the last day and try to crank something out... this doesn't work...ever.