Lesson Overview:
Students will learn about the function and form of levers. They will study parts of the lever and understand how to balance objects of various sizes and weights on a lever. Students will gain a deeper understanding of the function of levers by viewing the mobiles created by sculptor Alexander Calder. They will then experiment with balancing levers and discuss the process of finding equilibrium. Note: This lesson can continue to Planets in Balance where the Solar System is studied and replicated in mobiles using balance and levers.
Length of Lesson:
Two 45-minute periods
Instructional Objectives:
Students will:
- balance objects by changing and moving objects on a lever.
- differentiate between potential and kinetic energy.
- make connections between science and sculpture.
- name the function and parts of a lever.
- study and interpret the mobiles of Alexander Calder.
Supplies:
- Notebook paper
- LCD Projector
- Ruler
- Large crayon
- Two small paper cups
- Tape
- Collection of small objects, such as paper clips, marbles, and buttons
- Images of Calder’s works (may be projected or printed from the Internet)
- String
- Example of a mobile
Instructional Plan:
Introduction to Levers
Introduce to the students a simple machine called a lever. Note that levers are often used to do work with less effort, such as lifting heavy objects. There are also everyday objects that are levers, such as scissors. Show a lever to the class, pointing out the input and output arms and fulcrum (or pivot point). A simple lever can be made with a ruler and a large crayon. Also explain to the class the terms load and effort.
Explain the concept of balance, or equilibrium, on a lever. A lever is in equilibrium if the amount of effort is sufficient enough to lift the load, but the load is heavy enough to keep the lever in balance.
Allow students to practice balancing objects on a simple lever. A good activity to try with students, Shifting the Balance, can be found on the Illuminations site, a project of the National Council of Teachers of Mathematics. (You may decide to choose another activity in the unit, "Exploration of a Balance," to reflect the level of understanding of your students.)
Show a mobile to the class. Point out how it is made up of a series of levers in equilibrium. Levers and objects hanging from mobiles are placed so that all parts of the mobile are balanced. Point out the fulcrums and arms of the lever. Also explain to students how a mobile has potential energy when it is still. Demonstrate by lightly blowing on the mobile that the potential energy converts to kinetic energy, and vice versa when there is no air current.
Levers as Art: Alexander Calder
Introduce students to the mobiles of Alexander Calder. Explain that mobiles are kinetic sculptures—three-dimensional works that include moving elements. Display images of Calder’s works that depict a balance of objects, such as the following. (It is preferable to display images using an LCD projector; however, you may print out images of his work from the Internet.)
Foster a discussion about mobiles as a form of art. Ask students what they like or dislike about Calder’s work, and why. Ask students what comes to mind when looking at the mobiles. Note how the objects appear to float in space.
Now show students Calder’s Constellation Mobile, but do not reveal the title of the work. Ask students what they think the piece is titled and why. After some discussion, reveal the title, and ask students if they think Calder was effective in communicating a "constellation."
Explain to students that Calder’s mobiles were informed and inspired by his knowledge of physics, mathematical concepts, the cosmos, and astronomy. Before Calder enrolled in art school, he had received his mechanical engineering degree, a decision influenced by his fascination with construction and mechanical apparatuses and machines.
Experimenting with Balance
Allow students to practice balancing a simplified "mobile." To make this mobile, students should tie string around a ruler and tie or tape the loose end to a sturdy place, such as the edge of a desk. Students should then poke one hole on either side of the rim of a paper cup and insert the string through the holes. Tell them to follow the same instructions for another paper cup. Next, they should tie each cup to either end of the ruler.
Encourage students to explore and experiment with the position of the fulcrum, the weight of the loads in the paper cups (using various small objects), and the lengths of the strings. Students should make careful observations. When they alter one factor in their "mobiles," they should write down the alteration and the result in their notebooks.
Assessment:
Ask students to share their findings. What was challenging about finding the proper balance? What did they notice about moving and changing the position of the fulcrum, the weight of the loads, and the lengths of the various strings.
Extensions:
Go on to the second lesson in this unit, Planets in Balance.
Sources:
Print:
- Lipman, Jean. Calder’s Universe. Philadelphia: Running Press, 1976.
- Marter, Joan. Alexander Calder. New York: Cambridge University Press, 1993.
Media:
- Calder, Alexander. Mobile: By Alexander Calder. 24 min. National Gallery of Art. Videocassette. Available on loan from the National Gallery of Art.
Web:
Authors:
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Eileen Ewald , teacher
Thomas G. Pullen Arts Magnet School
Landover, MD
