Objectives: Students will learn about the function and form of levers and explore balance and energy through study of Alexander Calder’s kinetic mobile sculptures. Students will experiment with balancing levers and finding equilibrium through the creation of simplified mobiles. Afterwards, students can explore how the body can find equilibrium and create its own levers and simple machines with dance.
Vocabulary Addressed: Levers: (First, Second and Third Class, Fulcrum, Load and Effort) Potential Energy, Kinetic Energy, Equilibrium, Center of Gravity
Alexander Calder was an American sculptor born in 1898. Due to a strong interest in math and science, he chose to get a degree in mechanical engineering and applied his love of science to his art. He became famous for originating an art form called the kinetic sculpture, meaning a sculpture that moves. Calder invented the mobile, a type of kinetic sculpture made with delicately suspended shapes that move in response to touch or air currents.
Introductory Craft Activity: Identify and explore the world of Alexander Calder’s mobiles! Explain that a mobile is a cascade of levers. Each lever is suspended from above and has objects or other levers suspended from its ends.
- Name the functions and parts of a lever while creating Calder’s “series of levers in equilibrium.”
- Understand the difference between the three types of levers and apply the information to the mobile. What happens when you change the location of the fulcrum? What happens when you change the size of the load?
- Experiment with finding equilibrium by changing and moving shapes on the mobile. How do you find balance?
- Differentiate between potential and kinetic energy and apply the information to the creation of your mobile.
Guided movement exploration:
FINDING BALANCE: Explore how a dancer balances in many different lifts and positions.
How is it possible for a dancer to balance her entire weight on the tip of a pointe shoe, measuring one square inch? (The smaller the base, the harder it is to balance!) The key is that her center of gravity must be exactly in line with her base of support.
Center of Gravity: the location where the mass of your body is concentrated
Standing upright, an adult human’s center of gravity is located roughly at the center of their torso at about the height of the belly button (at about 55% of the total height).
The exact location of a character’s center of gravity will shift depending on the pose. For example, this dancer’s center of gravity rises a few inches when she raises her arms
When a dancer is balanced there are two forces acting upon them: one is gravity pushing them down, the other is the equal or opposite support from the floor pushing them up.
How are the mobile and a balancing dancer alike?
The dancer’s body, like the mobile, is full of potential energy. The dancer’s internal energy has to be constantly shifting and compensating to find equilibrium and balance. The mobile has external forces, like wind, air currents and curious hands that create kinetic energy and force the mobile to tilt back and forth to search for balance.
WHAT IS A LEVER AND HOW CAN I USE MY BODY TO EXPLORE THEM?
LEVER: A rigid bar revolving around a fixed point called the axis, or fulcrum
Fulcrum: Point at which the lever pivots.
Load: The object you’re lifting.
Effort: The force applied to make the object move.
Students will view photos of professional dancers and identify the class of lever demonstrated along with the load, fulcrum and effort. Discussion of the classes and study of the above chart can inspire exploration of both body shapes that represent levers and more complicated kinesiological analysis of how the body’s bones and muscles create their own levers in order to perform.
Above: The dancer’s 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.
Above: These dancers are representing a FIRST CLASS LEVER. Where is Sarah’s potential energy the greatest? How can you and a friend make a shape in which the fulcrum is situated in between the load and the effort? Can you make one by yourself?
These dancers above are performing a SECOND CLASS LEVER. Can you make their shape? How else could you show a lever in which the load is situated between the fulcrum and the effort?
The male dancers ABOVE and BELOW are demonstrating use of a THIRD CLASS LEVER. A third class lever is one in which the effort is situated between the fulcrum and the load. Every time you lift something, your arms are performing a lever. Can you perform a simple lift that demonstrates this type of lever?
This dancer is performing a Grand Battement, which is what dancers call a high, straight-legged kick. How is that a lever? Can you perform a Grand Battement? Where is your leg’s fulcrum, load and effort?
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