Discuss the use of the wedge to reduce friction. Have a variety of musical instruments. Ask students to identify what simple machines are present in these instruments. Make a list of each instrument and the simple machines that are evident. Examine how wedges have aided man historically.
Examples are stone knife, arrow heads, wooden stakes to stretch hides.
Ask students to list the many varied and unusual ways that wedges were used in the past. Compare this list with today's uses. As a result of its design, which is an inclined plane wrapped around a center post, a screw can support a lot of weight. The spiral of the inclined plane distributes the force over a greater weight. Use a student as a volunteer and butcher paper to create a screw.