Lesson Plans

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Summary of Included Lessons

The Foucault Pendulum for Grades 5-8

Learning Objectives: Students will be able to discover some of the behavior of pendulums and the special behavior of Foucault pendulums. Students will be able to prove to themselves that the Earth rotates. The first part gives a background to pendulums while the second part explores the Foucault pendulum.

• Part 1:  Question: What do pendulums do?

  How do you know that the Earth is turning? This is one of the trickiest of the everyday ideas to discover. What evidence do you have that the sun is not going around the Earth? Copernicus and Galileo used some sophisticated observations of the stars to show that the Earth revolved around the sun in the mid 1400s.

  A French man, Leon Foucault, was not satisfied with this explanation. He wanted to see evidence for himself that the Earth is turning. Leon was a college drop-out, not a professional scientist. What he did well was to make careful and patient observations and figure out how to make machines that help us see what our senses can not. He and a partner were the first to take photographs through a microscope. Next he figured out how to measure the speed of light and take good photographs of the sun and the stars. On January 3, 1851, he carefully set up a pendulum in the basement of his house and saw that the Earth was moving. We can see it too.

  But wait! What exactly is a pendulum and how does it work? Some people think of a playground swing. Others remember a Grandfather clock, the long part swinging back and forth, ticking and tocking to measure out time. Any set-up where something is attached or fixed at one spot and where the other end can hang down and swing back and forth is a pendulum.

  You can make a pendulum by hanging a shoelace from your finger and letting it swing. But if we want to observe what characteristics describe pendulums, we want to have a BIG mass hanging a long distance from the pivot on a string with which weighs nothing. In the real world, let’s try a bob of at least 25 grams hanging on a string about 40 cm long.

• Part 2:  What is special about a Foucault pendulum?

  Does the Earth rotate? How do we know? How does the pendulum show that? One of Newton’s laws of physics says that something that is moving stays moving unless it gets pushed by another force. This is part of why pendulums keep swinging in the same direction even when we turn them. The pivot puts a force on the pendulum but so do air currents or vibrations in the floor when people walk by.

The Foucault Pendulum for Grades 9-12

• Lesson 1: The Pendulum: Simple and Driven

  What is a pendulum? Why would you want to drive it and how do you build a driven pendulum?

  Learning Objective – Construct your own simple pendulums and be able to explain what is necessary to build a driven pendulum.

• Lesson 2: The Foucault Pendulum - The Plane of Oscillation Rotates

  Imagine what happens to a pendulum as it is turned in a circle. How would your observations of the pendulum’s behavior differ from observations of the Earth turning under the pendulum?

  Learning Objective - Relate the rotation of the plane of oscillation of the pendulum to the spin of the Earth.

• Lesson 3: The Movement of the Sun or the Earth

  Can we tell from the movement of the sun if the Earth is fixed Earth or spinning? What direction did the shadow on the sun dial move?

  The shadow cast by a sundial tracks the apparent motion of the Sun. The pointer (gnomon) interrupts the light and casts a shadow. The line from the shadow to the gnomon tells us the direction of the path that the light followed from the Sun to the sundial.

  Learning Objective – Understand how the fixed Earth/moving Sun model persisted alongside a moving Earth model.

• Lesson 4. Assessment

  Learning Objective - Evaluate the fixed Earth (moving Sun) model and the spinning Earth model to explain why the plane of oscillation of the pendulum moves and why the sun’s shadow moves.