Introduce the lesson by holding up the pinwheel from the previous day's lesson and asking the following questions:
Can something as simple as a pinwheel do work?
What changes can be made to a pinwheel to make it do work for us?
Allow the students a few minutes to discuss some ideas.
Ask the students if they remember the boy from yesterday's story, The Boy Who Harnessed the Wind? Allow the students a few minutes to review the story. "Today, I will show you a video of the man from the story, William Kamkwamba who built the windmill and managed to harness the wind to bring water to his village."
Show the video.
Show the students a diagram of William KamKwamba's windmill design and tell them they are going to investigate the design behind his windmill.
Place the students in groups of 4 students per group and give each group a copy of William Kamkwamba's windmill design (see attachments) and a crank flashlight. Each group will also be given a dynamo torch lab sheet (see attachment). Give the students time to explore the flashlight and complete the lab sheet, then ask the following question:
What makes the flashlight work?
Did you find any similarities between the flashlight I gave you and William's design?
Lead a discussion about any similarities they may have found (the turning of the crank caused the flashlight to power on - William used a bicycle dynamo in his windmill design to achieve the same results).
Ask the students what they noticed when they changed the speed of the crank (when they turned the crank faster, the light came on and was brighter - when they turned the crank slower, the light didn't come on or was much dimmer).
Draw students' attention to the statement, on the design sheet, William makes about modifying his design and increasing the number of blades from 3 to 4 in order to provide more power output and ask:
Why do you think he decided to do that? (because 4 blades gave him more wind power and more electricity just like cranking the flashlight faster made the light brighter).
Discuss with the students that instead of using his hand, William used the power of the wind to turn his dynamo to bring electricity to his village.
Tell the students "Now it is your turn to design and construct your own windmill." Working cooperatively in groups, students will design and construct a working windmill that will lift at least 5 coins up in a cup. Pass out the Windmill Design and Evaluation Sheet (see attachments) and have students brainstorm a design within their group. They will test their working windmill and record their data.
How many coins did their windmill lift?
What changes could they make to improve the amount of coins their windmill can lift?
To help wrap up this lesson, have students brainstorm together with their group to complete the Windmills at Work graphic organizer discuss other ways windmills can be used to make work easier for people. (see attachment)