# Exploring Kepler's Three Laws

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## Objective

Students will be able to define each of Kepler's Laws in a reading exploration activity.

## Context

In yesterday's lesson, students were introduced to universal gravitation and applied that knowledge with a PhET simulation. Today, the goal is to connect that knowledge with Kepler's Three Laws (while still using HS-PS2-4). I try to offer a variety of strategies to accomplish our goal, so the lesson starts with activation of prior knowledge in a first word activity. Then, students work in pairs to read all about Kepler's Three Laws (SP5) in an exploration activityFinally, students get to apply their new knowledge towards the end of class using yet another Phet simulation (SP2 & 8).

## First Word: Ellipse

10 minutes

Today, class starts with a first word activity that is meant to activate students' prior knowledge of ellipses. Most of my students are taking AP Calculus, so they've been exposed to ellipses as part of our math curriculum. As our introduction to planetary motion, I have the word ellipse written on the board when students enter the room.

Students start the activity when they write the word 'ellipse' vertically down the side of a blank sheet of computer paper. Then, in small groups of two or three, students create a short sentence or phrase that begins with each letter of the vertical word. The short sentence or phrase should also be relevant to the word ellipse or the elliptical motion of planets around the sun. I give them about 5 full minutes to work on their creations.

After the students have completed the activity, I ask students to share their best phrase or sentence. This quick sharing gives me an opportunity to see how much students remember about ellipses and how much they might already know about planetary motion. Also, when students are sharing they might activate prior knowledge in another student with their contributions.

30 minutes

Because I know from our introductory activity that my students have a working knowledge of ellipses, students choose a partner and take a computer from the cart at the front of the room. As the computers are booting and after students have seated themselves next to their partner, I give each of my students a copy of the Kepler's Laws exploration. This document is a guideline that helps students identify the absolute minimum material they should record into their physics notebooks before moving on to the next activity. I let students know that they can read aloud or individually, but the point of them being in pairs is to discuss and determine the most important parts of the text.

Once they've opened the document, the students follow the link to the Kepler's Three Laws section of the Physics Classroom. At this website and still in their pairs, students read through the text and use the document to guide them through the process of defining each of Kepler's Laws. Students identify situations that use Kepler's Laws, copy narrative and an image to describe each of the laws, and write example problems with solutions during the activity. I've purposely chosen this information for students to explore because it is information that is useful in the next part of the lesson.

While students are working, I walk around with the answer key to ensure they are actively engaged in the learning process. To me, this means that they are on the proper website, reading or discussing some component of Kepler's laws, and writing down a thorough set of notes. When I walk around, I spot check their written work and engage students in questions such as "How does this relate to what you've learned in math classes about ellipses?" or "How is the gravitational constant used to justify Kepler's Third Law?" The goal of this reading exploration activity is to give students a solid foundation of Kepler's laws before they move on to the next part of the lesson. Since students need their written information in the next part of the lesson, I do not collect their work.

## Exploring Kepler's Laws with a Simulation

10 minutes

After students are done reading about Kepler's Laws, they use a computer simulation that allows them to be more active in their learning. The Gravity & Orbits simulation allows students to visualize how gravity controls the motion of planets and objects within our solar system. It also gives students an opportunity to visualize the relationship between the sun, earth, moon, and space station.

Since students are already in pairs and have a computer from the previous activity, no classroom organization is necessary before I pass out the activity directions to each student. The activity sheet is meant to direct the students in their learning and allows them to apply what they've just learned about Kepler's Laws. Students have the choice to write their answers on a separate sheet of paper or to type and then share their answers electronically.

While students are working, I walk around to ensure they are actively engaged in the learning process. This means that they are on the proper website, reading or discussing some component of the simulation, and writing down appropriate information from the simulation. When I walk around, I'm spot checking their written work and engaging students in questions such as "Which one of Kepler's Laws do you currently see in action?" or "Which tab do you prefer, the cartoon or real-world version?"

When there is approximately two minutes prior to the end of class, I ask students to put the computers back on the cart and return to their seats. I also tell them at this point that if they were not able to finish the simulation questions, the questions are homework. My announcement and students putting away their computers is how class ends today.