# The Physics, Astronomy and Mathematics of the Solar System

## The Physics of the Planets: How 16th and 17th Century Physicists Helped Us Understand Our Solar System

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## Activities and Lessons

Activities to introduce students to motions of the planets will include working outdoors with chalk on pavement to draw elliptical orbits identifying foci and determining eccentricity. Also, students will be acting out the movements of the sun and the planets, including rotation and revolution, in groups of ten. Students will also create diagrams of the orbits of various planets and produce illustrations that show how planets sweep out equal distances in equal time in their orbits around the sun. Basic physics lessons will include calculation the speed of toy cars by measuring their distance traveled.

The final project of this unit will be a computer slide show presentation created during sessions in the school's tech lab. The rubric will include basic facts about the sun, planets, moons and other objects in the solar system such as: names, sizes and distances from other objects. Each student will do an individual project on one planet or one group of non-planetary bodies; dwarf planets or comets. The emphasis will be on the students' demonstration of each planet's or object's motion and how it is determined according to basic physics laws of motion.

### Drawing Ellipses Activity

Lesson Objective: Students will be able to identify and draw ellipses and their foci.

Initiation: Teacher will begin class by asking students: What shape does the Earth make as it revolves around the sun? All answers will be accepted (about 4-5) and recorded on the chalkboard or on chart paper to refer to during lesson closure. Also, to warm students up to the lesson other questions can be asked such as: Who has drawn a circle using a compass? Who has heard the word "ellipse" before?

Materials:

Nylon cord (ten feet for each group of students)

Sidewalk chalk (three pieces for each group of students)

Teacher created handout with directions (one per student)

Procedure:

Assign students to groups of three to work together.

Read directions aloud to the class

Ask students if there are any questions about the procedure.

Walk students outdoors where there is pavement that is adequately smooth and clean for drawing.

With another adult, or student helper, demonstrate the drawing of a circle.

1 Tie the ends of the cord together.

2 One participant puts the cord around his or her waist.

3 Participant two secures the chalk inside of the end of the cord.

4 Participant one stands in one spot while participant two or participant three draws a circle around participant one.

Direct students to draw their circles

After circles are completed ask the students questions about their process and relate observations made by teachers and other students. For example:

1 What did you experience while making these drawings?

2 Do most of the drawings look like circles?

3 Why do you think this circle looks a little crooked?

4 How many central points did each circle have?

Next, direct students to draw their ellipses.

1 Participants one and two stand a few feet apart with the cord around both of their waists

2 Participant three holds the chalk inside of the cord so that the cord can move against the chalk while the ellipse is being drawn.

After Ellipses are completed ask the students questions about their process and relate observations made by teachers and other students.

For example:

1 What did you experience while making these?

2 Do these drawings look different than circles?

3 What do they have in common with circles?

4 How are they different from circles?

5 Were they harder to draw than circles?

Choose one of the drawings to use as an example. Point to it or stand in it while teaching. Point out the difference between the circle with one central point and the ellipse with two foci. Explain that planetary orbits are ellipses and that the sun is one focus of the ellipse. And that there is not anything that is important to the orbit at the second focus. Direct students to go to their own drawings and stand on:

1 Your circle

2 Your ellipse

3 The central point of your circle

4 One focus of your ellipse

5 The other focus of your ellipse

Then ask questions relating planets, the sun and their orbits to the ellipses. For example:

1 Which drawing is more like Earth's orbit?

2 Where would the sun be if that is Earth's orbit?

3 What about the other focus?

Assign students to write a paragraph about what they learned from the activity. This can be done as a wrap up exercise or as a homework assignment depending on the amount of time available for the lesson.

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Measuring Speed Activity
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Lesson Objective: Students will calculate the speed of an object by measuring distance divided by time.

Initiation: Ask students: Have you ever seen a speed limit sign? Have you ever known anybody who has received a speeding ticket? What is the speed limit on the highway? How is the speed of a car measured? Then briefly explain to them that they are going to measure speed in centimeters per second today.

Materials:

toy cars (six to twelve centimeters in length, self winding if possible)

meter sticks

smooth flat surface - at least three meters long, sixty centimeters wide

stop watch(s)

masking tape

Procedure:

Step 1. Divide students into groups of two or three each.

Step 2. Have each group of students create a three meter long race track on a lab table or other smooth surface by taping two meter sticks, parallel to each other, fifty centimeters apart.

Step 3. Have students pre-measure and record the distance of their race track

Step 4. One student rolls the car on the track while another times it.

(Repeat step 4 for a total of three trials for each group)

After all trials are completed show students the formula for calculating speed(see figure 8).

Figure 8

Speed = distance (in centimeters) / time (in seconds)

Step 5. Have students insert their measurements into the formula and record their data to determine the speeds of each car. This should be written as centimeters per second (cm/s).

Closure: Ask students: Why is it important to determine speed? Is it important to know the speed of objects traveling in the solar system? Why?

Follow up activities can include:

Find the average speed for the class.

Find the speed of other objects such as tennis balls or hockey pucks.

Create hypotheses to explain why some cars or other objects went faster than others. This could be a lead in to teaching friction or force.

Determining how long it takes an object to travel a certain distance at a given speed. For example: How long does it take a car traveling 60km/hour to travel 5 km.

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Final Project: Computer Slide Show Presentation
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Students will be instructed to create a computer slide show presentation to demonstrate their understanding of the movements of the planets. The project will consist of five to seven slides on an assigned planet. Each student will be assigned one planet or group of planetary objects such as: comets or dwarf planets. Information on slides should include physical facts, satellites, period of rotation, period of revolution, and history of the object(s).

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