Explains what a screw is; shows how screws were used in ancient Egypt, Greece, and Rome; presents examples of everyday items that screws hold together; and includes a related activity.
Explains how pulleys work, introducing fixed and moveable kinds, presents examples of pulleys used in the past and in everyday contemporary life, and includes a related activity.
Explains how levers work, discussing the load, fulcrum, and effort in first-, second-, and third-class levers; presents examples of levers used in the past and in everyday contemporary life; and includes a related activity.
Explains how inclined planes are used, presenting examples from the past and in everyday contemporary life; discusses the combination of an inclined plane with other simple machines in an escalator; and includes a related activity.
