Unit 3: Gravity
Lesson 4: Re-Creating Galileo's Pendulum Experiments- Part 1
5E Lesson Planning:
I plan most of my science lessons using the BSCS 5E Lesson Model: Engage, Explore, Explain, Elaborate, and Evaluate.For a quick overview of the model, take a look at this video.
I use this lesson model because it peaks the students' interest in the beginning during the "Engage" portion and allows for the students to actively participate in the investigations throughout the subsequent steps. The “Evaluate” component of the 5E Lesson Model can be used in many ways by the teacher and by the students.
In this Unit students will do some investigations about gravity. They will learn about how the planets stay in orbit around the Sun and will re-create Galileo’s pendulum experiments. They will also learn about Sir Isaac Newton’s work and his Laws of Motion as they relate to the idea of gravity.
In this lesson, students will create a pendulum or swinger and explore how it works. This is the first lesson in a 3 part investigation with pendulums.
The materials needed for this investigation per group are:
Other supplies needed: scissors, watch or clock with a second hand, masking tape, and extra copy of the direction sheet to project or made into a poster for reference.
Next Generation Science Standards:
The NGSS standards that will be covered in this unit/ lesson are:
5-PS2-1. Support an argument that the gravitational force exerted by Earth on objects is directed down.
Disciplinary Core Ideas: This lesson aligns to the Disciplinary Core Ideas of 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)
Cause and Effect: Cause and effect relationships are routinely identified and used to explain change. (5-PS2-1)
Science & Engineering Practices:
Engaging in Argument from Evidence: Engaging in argument from evidence in 3–5 builds on K– 2 experiences and progresses to critiquing the scientific explanations or solutions proposed by peers by citing relevant evidence about the natural and designed world(s). Support an argument with evidence, data, or a model. (5PS2-1)
I ask the students whether they have ever been on a swing on the playground. After a show of hands I ask if they know how a swing works. I tell them to do a Round Robin with their groups to describe this to each other. I walk around and listen for student responses. These include:
I then ask the students about why the swing eventually stops or comes back to the center point. Some students mention that if you aren't using your legs to move the swing, then it stops. A few students mention that it's gravity that makes the swing eventually stop.
I remind the students of the previous lesson where we learned about Galileo and I tell them about how he decided to do experiments based on something he observed. While he was at his church in Pisa, he saw that when the lanterns had to be lit they were pulled back to light them then let go. He observed that the lamps swung back and forth for a period of time. He measured this "period" by using his pulse. He decided to re-create this phenomenon by making pendulums by tying a weighted "bob" to a string and having it swing back and forth. He again measured the timing of the swings or "period" by using his pulse and found that the cycle of the swinging pendulums remained the same even when the distances traveled by the pendulums was different.
I explain that we will be making our own pendulums by using paperclips, string, pennies, and tape. I give the students the Handout to show them how to make their own pendulum and go over the directions. I also make sure to set up a Champs for Science Lab expectation for them, especially since it will be tempting for them to swing the pendulums in different ways and I want to reinforce that we need to be safe when we are making and using these tools.
I model for the students how to make their pendulums and make sure that they follow the directions on the handout. The students will work with a partner to complete the task. I support the students with the construction as needed. (insert photos of students making their pendulums)
After the students have made their pendulums, I ask them to double check their measurements to make sure that they were accurate. The reason for this is that the length of the string will be one of the variables that will be changed in a later investigation. Here are pendulum set up #1 and Pendulum set up #2.
I ask the students how many times they think their pendulum will swing in 15 seconds and I then tell them that they will be designing an experiment to find out. I also ask them to think about why the pendulum is swinging and why it eventually stops. Here are their Pendulum predictions (the larger numbers)
I decide to keep this part of the investigation open- ended. If you want to keep it structured, you will want to guide the students more during this part of the lesson, otherwise, this will be a great place for students to discover the different variables that would affect the swinging.
When I say "Go", the students release their swingers and count the number of swings (in their head) for 15 seconds- I keep track of the time. They keep counting until I say Stop. I ask the students to report their findings.
Every group of students report different numbers and I ask them why they think this happened when everyone's set up is the same. Most likely there will be a difference in the number of swings that the students counted and we have them talk to their science groups as to why this might happen. I ask the students share out their answers and I record their responses on the board so we can refer to it later. The students state that everyone released the pendulum from a different height or that they might not have released the pendulum at the right time. One student also mentioned that they didn't know how to count the swings. I tell them that they need to count when the pendulum swings out and then back to the starting position as one swing or cycle.
After this discussion, we decide on a procedure that we can all follow to make sure we have a controlled experiment. We decide to hold the penny (or bob) parallel to the floor and to keep the string straight before releasing it. The students also mention that they need to count only the cycles in 15 seconds and that everyone needs to release the bob when I say "GO". We also double check their pendulum set-ups (some students had pencils that weren't quite flat and their pendulums hit the side of the desk).I write the procedure on the board (Pendulum criteria):
We go through these procedures again so that the students all come up with the same number of swings/ cycles. The magic number is 12.
I then ask the students about what things they could change on their pendulums to change the number of swings. They mention that they could change where they release the penny (release point), they could change the number of pennies or mass, and they also could change the length of the string.
I tell the students that what they described were variables and I write this term on the board. I ask the students to say they word and ask if they've heard it before. I give them the definition of variables and have them write in down in their Science Notebook:
variable: anything you can change in an experiment that might change the outcome.
I also define what the penny represents in the pendulum (the bob which is a mass) and we define pendulum and discuss the term cycle. I tell the students that in the next investigation they will be changing the variables to conduct controlled experiments to see if the outcomes are different.