Materials

• blank paper
• 3 plastic drinking straws kit
• 1 sheet of construction paper (28 cm x 21 1/2 cm)
• 1 spool of thread
• scissors
• tape

Involve students in a discussion about mobiles. If possible, have examples or pictures of mobiles available for them to observe. Invite students to share their observations. Encourage them to apply what they know about the center of gravity as they explain their ideas about how a mobile is constructed. Challenge student groups to use what they know about the center of gravity to construct a mobile with six unusual shapes, three straws, and thread.

1. Each group member cuts out at least one unusual shape from the construction paper. (If there are less than six students in the group, decide which shapes should be duplicated to give a total of six shapes.)
2. Discuss and decide how the shapes and straws are to be arranged on the mobile.
3. Draw a picture of the arrangement.
4. Construct the mobile using the materials provided.
5. Make any necessary modifications to balance your mobile.
6. Write a description of, and explain, any changes made to your mobile design.

Student groups may select to attach the unusual shapes to the mobile vertically or horizontally. Students may also choose to tape the thread to the straws, or pull it through the straws. Modifications to the mobiles are encouraged, if necessary. Whatever position or method is used, the students need to be reminded that the shapes, as well as the straws, should be balanced on the mobiles.