Split the class into groups of two or three and give each group a length of string, tape, a drinking straw, and a balloon. Ask each group to tie their string to a chair and blow up the balloon as much as possible. One student in each group tapes a straw to the top of his group's balloon and slips it onto the string while another student in the same group holds the balloon shut. The other end of the string gets tied to another chair and the students let go of the balloon. The force of the air leaving it propels the balloon forward. After the first run, each group should fill their balloon with a different amount of air and record which amount propels it forward the most and least, using a ruler to measure how far they go.
Split the class into groups of four. Ask one student in each group to use waxed paper or an empty milk carton to create a different boat design (flat bottom, round bottom, deep V shape, or shallow V shape). Tell the other students to fill a small plastic tub with water and tape a piece of soap to the back of each boat. The soap will propel the boats forward in the water by breaking its surface tension. Ask students to record which boats move the fastest. They will learn about aerodynamics as they see how the different shapes allow some kinds of boats to move faster than others.
Give students a sheet of paper, scissors, and a few pairs of pinking shears. Instruct them to cut the paper vertically into thirds and make a snip in the long side of each, about halfway down, then fold the bottom up to hold them in place. Tell them to cut the top of each strip in half vertically, one with the scissors and the other two with pinking shears. They should then fold one side of the cut down to the right and one to the left to create flattened wings. As they drop each whirlybird from a high place, students should record which flew the longest, and why. This experiment will demonstrate basic principles of aerodynamics. The shapes made by the pinking shears should make them fall faster than the ones cut with regular scissors. They are less aerodynamic than the other whirlybird.