Day Two of Plaid Pete is Going Down!

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SWBAT explain that the orbit of the moon around the Earth is due to Earth's gravitational pull and greater mass.

Big Idea

Why does the moon orbit the Earth? Students engage in an investigation that leads them to understand the force of Earth's gravity on the moon.

Setting Up the Investigation

This is Day Two of a Two Day Lesson.  Click here for Day One of  Plaid Pete is Going Down!

On Day One of this investigation, students engaged in a guided exploration where they learned about the effects of gravity on Earth.  On this second day, students will further their understanding of the effects of mass on gravitational pull by working with models that simulate the relationship between Earth and the moon.

Connection to The Next Generation Science Standards

In this investigation, students begin the work that will lead them to explore the Disciplinary Core Idea of Earth's Place in the Universe:  The Universe and its Stars -  that the sun is a star that appears larger and brighter than other stars because it's closer, and stars range greatly in their distance from Earth. (5-ESS1-1); Earth and the Solar System - that the orbits of Earth around the sun and of the moon around Earth, together with the rotation of Earth about an axis between its North and South poles, cause observable patterns.  These include day and night; daily changes in the length and direction of shadows; and different positions of the sun, moon, and stars at different times of the day, month, and year. (5-ESS1-2); Motion and Stability:  Forces and Interactions - that the gravitational force of Earth acting on an object near Earth's surface pulls that object towards the planet's center.  (5-PS2-1) and the Crosscutting Concept of Patterns  - Similarities and differences in patterns can be used to sort, classify, communicate and analyze simple rates of change for natural phenomena. (5-ESS1-1); Scale, Proportion, and Quantity - Natural objects exist from the very small to the immensely large (5-ESS1-1); and Cause and Effect - Cause and effect relationships are routinely identified and used to explain change (5-PS2-1).

Please Note:  The Lexile Level for Plaid Pete is Finding Earth's Place in the Universe - Lab Scenario Sheet Lesson 4  is 770  (5th Grade Range is 740 - 1010).

The Preparation Time for This Investigation is approximately 30 minutes.  (Approximately 20 minutes will be spent constructing the ball assemblies).

Lab B was adapted from an experiment included in the NASA SCI Files:  The Case of the Phenomenal Weather found at

Materials Needed:

One 4 inch length of PVC pipe (approximately 3/4 inch in diameter)

2 large metal nuts per team

Small metal nuts 

1 8 oz. fish weight per team

1 rubber or smaller diameter ball per team (Drill 2 holes in each ball, loop string around ball and tie to secure.  Leave ends long and loose so that students can measure to a length of 1m.  I was able to find a package of 5 balls.)


Meter Stick

Day One

Materials Needed:

One copy for each student of Plaid Pete is Finding Earth's Place in the Universe - Lab Scenario Sheet - Lesson 4

One copy for each student of Plaid Pete is Finding Earth's Place in the Universe Lab Sheet - Lesson 4

One copy of Plaid Pete is Finding Earth's Place in the Universe Word Wall Cards - Lesson 4

One paper copy for each student of Plaid Pete is Finding Earth's Place in the Universe Word Wall Cards - Lesson 4

One clear plastic cup per team

Two books per team (e.g. dictionaries)

One ruler per team

One tape measure per team

One paper clip per team


Focus & Motivation

5 minutes

I tell my students, "In yesterday's investigation you learned about the force of gravity, and how it pulls objects on or near Earth, towards its surface.  Today, we are going to explore what happens to a very special object that is outside of Earth's atmosphere - the moon. Have you ever wondered why the moon doesn't just come crashing down on all of us?  We have learned that gravity pulls everything towards Earth's surface - so why doesn't the moon get pulled towards Earth's surface as well?"  

I had hoped for a few responses - "deer in the headlights" faces are looking back at me.  I can see that this thought hasn't occurred to them before.  This is a great time to share our learning objectives for the day:

Learning Objective & Success Criteria

Note:  Consistent with the Sheltered Instruction Observation Protocol, I am now including a language objective with each lesson.  These objectives were derived from the Washington State ELP Standards Frameworks that are correlated with the CCSS and the NGSS.

I share the learning objective and success criteria:  

Learning Objective:  I can explain that the orbit of the moon around the Earth is due to Earth's gravitational pull and greater mass.

Language Objective:  I can explain how someone's reason supports their argument  [ELP.4-5.6]

Success Criteria:  I can complete all sections of my lab sheet, and participate in a class discussion.

Guided Exploration

25 minutes

Introduce the Task

I ask my students to take out their Plaid Pete is Finding Earth's Place in the Universe Lab Sheet - Lesson 4 from yesterday.  I explain that today we will be completing this series of investigations on gravity.  We read through Lab C.  I ask my students to complete their job lists, before they get their materials.

I explain that what they will be investigating, is what it takes to keep the ball from the assembly into orbit - it is a "delicate balance of speed and gravity."  So I want them to pay close attention to the changes in speed that are needed to keep the ball in orbit, and the effects that gravity have on the ball.  This means paying attention to when the ball is able to complete a circular motion, or when the ball begins to fall.

Students Conduct Investigations

Once my students have completed their job lists, they get their materials and begin working. In order to assure that their is an even balance between the ball at one end of the string, and the nut at the other end of the string, students check using a balance.  It is necessary to add a small nut to the end with the ball.


When they have their assemblies constructed, I move them outside (away from the windows!).  I also make certain that the metal nuts are securely tied and students are widely spaced away from each other before they begin spinning.  

In Video Clip 1 students are getting the hang of getting and keeping the ball into an orbit. They learn it is fairly easy when the mass is balanced on both ends.  In Video Clip 2, this student learns that he has to work a little harder when he adds a second metal nut to the bottom of the assembly.  By Video Clip 3, an 8 oz. fish weight has been added and students learn that it is next to impossible to move the assembly fast enough to keep it in orbit!  How does the moon stay in orbit then?  I guess we need some more information!

I prompt students to carefully construct their models. They are apt to get excited in the fun of the event, rather than the Science of the event - so it is important to keep them on task! 

These pictures capture some close-up views of the ball assembly.  This is the ball with a hole drilled through  This is the ball assembly with washer weights.  This is a close-up of the ball assembly with washer weights.  Finally, this is a close-up of the fish weight added to ball assembly


20 minutes

Introduce the Video

I play the video Why Doesn't the Moon Fall Down from PBS Learning Media.  It explains to my students how the right combination of speed and gravity, just like the assemblies they have created, causes the moon to fall around instead of into the Earth.

Making Sense of the Investigation

After the video plays, I write this first question on the whiteboard:

What happened when you put your "satellite" (ball) into orbit with one metal nut at the bottom?

I ask my students to turn and talk.  I ask my students to share out.  They say:  "It took some practice to get it into orbit"  I ask my students to turn and talk, answering the question, "What caused that to happen."  I call on a team to share and the student answers, "Gravity pulls everything towards the center of the Earth, so we had to get the speed of the ball fast enough that it wasn't pulling down."  I specifically ask students to specify how another student's reason supports their argument.  

I write the second question:

What happened when you added mass (a metal nut) to the bottom, or increased the gravitational pull?

I ask my students to turn and talk.  I ask my students to share out.  They say:  "We had to make the ball go faster to keep it in orbit."  I ask my students to turn and talk, answering the question, "What caused that to happen."  I call on a team to share and the student answers, "The mass increased, so the gravitational pull at the bottom increased."  I again call on another student to elaborate on how reasons were supported by evidence.

I tell my students, "We have learned some amazing new information about gravity.  Let's see if we can now revise our thinking!"

Reflection & Closure

5 minutes

Revising Using the "Line of Learning"

I ask my students to use their green pens (Green is for growing!) to draw a line of learning underneath the previous answers on their lab sheets.  I ask them to think about what they have learned in this investigation, and revise their answers.  

I am excited to see what they will write.  I love seeing the growth they demonstrate!  I have those students who really stretch themselves and use their scientific vocabulary, but the average students in my class demonstrate responses similar to the student sample below.  This is rigorous, difficult content.  I am pleased with successive approximation at this point!

This is an example of the pages from one student's notebook:  Page 1, Page 2, and Page 3.


Tomorrow morning for their "Do-Now" activity.  I will post the following question on the board:

Which has a larger gravitational force, Earth or the Moon?  Why?

We will discuss our answers before the next investigation.  I want to make sure my students to understand this concept:

Objects with a larger mass have a greater gravitational force than objects with a smaller mass.