Can Hero Engines Tell the students they are going to do an experiment to find out if there is any relationship between the size of the holes punched in the Hero Engine and how many times it rotates. Ask students to predict what they think might happen to the rotation of the Hero engine if they punched larger or smaller holes in the cans. Discuss possible hypotheses for the experiment. Provide each group with the materials listed for Part Two. The nails should have different diameter shafts from the one used to make the first engine.
Older students can measure the diameters of the holes in millimeters.
Since there will be individual variations, record the average hole diameter. Have the groups make two additional engines exactly like the first, except that the holes will be different sizes. Discuss how to count the times the engines rotate. To aid in counting the number of rotations, stick a brightly-colored round gum label or some other marker on the can. Tell them to practice counting the rotations of the cans several times to become consistent in their measurements before running the actual experiment.