Third grade students are learning about simple machines. In order to learn more about levers they all conducted an experiment in small groups. They worked to test the effort of a lever when a fulcrum is placed at different points. First, students taped a marker onto the edge of the table to act as a fulcrum. They placed a box of pencils at one end of a ruler which was their load they were trying to lift. At the other end they had a zip bag that was taped on (use high quality zip bags- the first run we did, the marbles ripped the bottom of the bag and, well, you can image 100 marbles rolling EVERYWHERE).
They first placed the ruler onto the fulcrum at the 2 inch mark. Next, they added in marbles and counted how many it took to lift the box of pencils. Next, students moved the fulcrum down to 3 inches and repeated the experiment. They did this at various points to see how moving a fulcrum changes the effort. If I did this again, I would have students test at just 3 or 4 positions, rather than each inch. It took awhile and was a bit too repetitive for so many trials. In addition, I would add a spot on their recording sheet to put an estimate before testing each mark. Overall, though they understood the concept and were excited about the experiment.