Recreating Galileo's Leaning Tower of Pisa Investigation

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SWBAT explain the rate at which heavy and light objects fall.

Big Idea

In this lesson, students will use the Scientific Method to test the rates at which a tennis ball and a plastic ball fall to Earth.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at, How Inquiry-Based Learning Works with STEMvery clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will develop an understanding of gravity while focusing heavily on the 5th Grade Engineering and Design standards. In the first few lessons students will explore the relationships between gravity, weight, and mass. Then, students will apply their understanding of gravity to engineer and design parachutes and roller coasters.   

Summary of Lesson

Today, I will open the lesson by posing the question, "Which ball (a tennis ball or plastic ball) will hit the ground first?" We watch a video on Galileo's Leaning Tower of Pisa Investigation. I will also weave the Scientific Method into this lesson by continually referring to posters on the wall. Students will then explore how weight affects the rate in which objects fall to the ground by conducting an investigation. At the end of the lesson, students will reflect upon their collected data and apply their new understanding of objects and gravity by writing a conclusion. 

Next Generation Science Standards  

This lesson will address the following NGSS Standard(s): 5-PS2-1. Support an argument that the gravitational force exerted by Earth on objects is directed down.  

Scientific & Engineering Practices

For this lesson, students are engaged in Science & Engineering Practices 3 and 4. 

Science & Engineering Practice 3: Planning and Carrying out Investigations - Students will plan and conduct an investigation and will take the precautions necessary to set up a fair test. They will also be making predictions and recording observations. 

Science & Engineering Practice 4: Analyzing and Interpreting Data - After the investigation, students will use use their collected data to draw evidence-based conclusions.

Crosscutting Concepts

To relate content across disciplinary content, during this lesson I focus on Crosscutting Concept 3. 

Crosscutting Concept 3: Scale, Proportion, and Quantity - Students will explore scientific phenomena by recognizing that the tennis ball has a greater mass than the plastic ball. Also, students will determine that an object's mass does not affect the rate at which it falls to Earth. 

Disciplinary Core Ideas

In addition, this lesson also aligns with the Disciplinary Core Idea, PS2.B. Types of Interactions: The gravitational force of Earth acting on an object near Earth’s surface pulls that object toward the planet’s center. (5-PS2-1)

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  


30 minutes

Lesson Introduction & Goal 

I introduce today's learning Goal by writing it on the board: I can explain the rate at which heavy and light objects fall. I ask students to write the goal on a new page in their journals. 

I continue: During the past three investigations, we took a close at the differences between mass and weight. Today, we're going to switch gears a bit and focus more on the way objects are pulled toward Earth. 


Today, you get to complete an investigation! But, before we begin, we need to take a closer look at the Scientific Method. On a new page in your science journals, please write the title, "The Scientific Method." As we discuss the Scientific Method today, I'd like for you to record the steps on this page in your science journal. To support the categorization of new information, I also encourage students to color-coordinate their steps with the posters. For example, the poster for step one is red, so students use a red marker to write "1. Ask a Question."

Here's an example of a completed student journal from today's investigation: 


I refer to the The Scientific Method posters on our science wall and explain: The scientific method is a step-by-step approach to finding the answer to a question. Scientists perform investigations to find the answer to a question. I model how to take notes on Scientific Method in student journals: Scientific Method Teacher Model.

(As a side note, I created these posters in conjunction with The Engineering Method posters so that students can easily see the connection between these two processes. I will introduce the Engineering Method in a few days and I don't want students to get confused!)

First, we will start by asking a question.

I want to inspire interest in today's lesson and capitalize on student curiosity, so I pose an authentic question. Holding up a tennis ball and a plastic ball, I ask: What would happen if we dropped a tennis ball and a styrofoam ball from 1 meter high at the same time? What would happen? Which ball would hit the floor first? 

Students point out that both balls would fall toward the floor as the force of gravity pulls objects toward the center of the Earth. Then, one student said, the heavier tennis ball will hit the floor first.

Before moving on, we took notes on asking a question in our journals: Ask a Question Teacher Model.

Galileo's Leaning Tower of Pisa Investigation

The next step in the Scientific Process is to do background research on the topic and to find out more information. 

Let's see if anyone has ever conducted a similar investigation! This is the perfect opportunity to show a video of Galileo's Leaning Tower of Pisa Investigation.

Students write "Background Research" in their journals and take bulleted notes: Background Research Teacher Model.

Weighing Objects

Prior to the lesson, I lay out the following supplies on the counter for today's investigation: Supplies on the Counter. To find out more information, I ask each group of three students to gather the following materials: tennis ball, styrofoam ball, plastic baggy, a spring scale, and a gram mass set. I then review how to read the (Decimal Scale Review) and ask students to determine the weight of each ball using the spring scale. This is an important part of this investigation as I want students to clearly see that one object is heavier than the other. 

Students create a simple data table in their journals to record the mass of each ball: Weight of Balls Data Table.

A Fair Test

I hold up the two balls at different heights and ask: If we want to see which ball will hit the floor first, would I drop the tennis ball from one meter off the ground and the styrofoam ball from two meters off the ground? Turn and talk! 

After some time, students share with the class that that "wouldn't be fair." "You have to drop them from the same heights." So what you are saying is that we need to keep all conditions the same for each ball in order to conduct a fair test? What else might we need to keep the same?Students suggest: same type of floor each ball hits, same way each ball is dropped, and same location of the observer. 

This is the perfect opportunity to share a new vocabulary poster, Fair Test Poster.

Planning the Investigation

You are now ready to move on to the next step in the Scientific Method, Design Investigation and write procedure. I ask students to help come up with the following procedures: 

1. Drop both balls from the 2 meters high.

2. Observe and record which ball hits the floor first.

3. Repeat steps 1-2 three times to make sure the results are accurate. 

Again, students document how to design the investigation in their journals: Design the Investigation Teacher Model.  

Forming a Hypothesis

Next, we need to form a hypothesis. A hypothesis is a fancy name for a prediction. I provide students with the following prompt and restate the question: Which ball would hit the floor first?  

I predict the _______________ will _______________ because.... 

By this time, most students were convinced that both balls would hit the floor at the same time. I call on a student and write his hypothesis as a model for the class: Create Your Hypothesis Teacher Model.

I explain to students that it's okay if our predictions end up being incorrect. The goal of science isn't to always have correct predictions. If we already knew the answer to the investigative question, there would be no point in completing the investigation. The true goal of science is to learn how the world works through the exploration of knowledge and scientific phenomena. 


10 minutes

Data Table

I refer to the Scientific Method Posters: Now that we are all set for the investigation, it's time to test your hypothesis by DOING the investigation.

I ask students to construct a two column data table in their science journals, labeling the first column "Trials" and the second column, "Results." Here's a model of this: Data Table Teacher Model. Under the "Trials" column, we wrote Trial 1, Trial 2, and Trial 3. I stress the importance of recording observations in the "Results" column before going on to the next trial.  

Monitoring Student Understanding

Once students begin working, I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. What have you found so far? 
  4. Has your thinking changed? 
  5. What evidence do you have? 
  6. How did you decide _____?
  7. Has your thinking changed? 
  8. What conclusion can you draw about ____?

Student Conferences

During this conference, Are you sure?, the students were convinced that the tennis ball hit the floor first. I ask them to show me again. I notice that the tennis ball bounces higher than the styrofoam ball, making it seem like it hits the ground first. I suggest that we record the investigation so that they can view a video of both balls hitting the floor: Recording the Drop. Later on, we show this video to the class to clear up any students convinced otherwise! 

Reflect & Apply

20 minutes

Sharing Findings

Now that students have built meaning and understanding by observing, questioning, and exploring, it is important to provide students with the opportunity to share their findings.

We are now ready to move on the next step of the Scientific Method: Analyze your results and draw conclusions. I invite students to share their investigation results aloud. Also, I encourage students to compare their data and determine why groups may have achieved different results. 

Drawing Conclusions

Now that we have analyzed our data, we can now Draw Conclusions, which is the last step of the Scientific Method. I model how to write "Draw Conclusions" in science journals: Draw Conclusions Teacher Model. Using a Conclusion Prompts poster, I provide the following prompts to help scaffold this assignment: 

1. My prediction was correct/incorrect because... 

2. During the investigation, (explain the results)...

3. I have learned that...

Communicating Results

As students finish, I ask them to complete the last step of the Scientific Method by sharing their conclusions with others in the class. We simply write "Share Conclusions" in our journals without taking notes below: Communicate Results Teacher Model. During this time, I also encourage students to bring along a red pen to make revisions to their conclusions. I specifically ask them to find ways to make their conclusions more clear and understandable to the audience.