A)The first description of lever:
Displaying a picture of heavy object and asking them how can we hold it or move it.
Collect their responses and make comments.
Open a discussion about man in the past
and how he could perform the heavy tasks.
Helping them to reach the conclusion that :
Levers were the first machines man invented.
Levers were first described by the Greek scientist "Archimedes" in the year 260 B.C