Unit 3: Gravity
Lesson 6: Re-Creating Galileo's Pendulum Experiments- Part 3
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 use a pendulum to analyze the variable of length to graph and predict the different number of swings. They will be looking at dependent and independent variables, and recording data on a two-coordinate graph. This is similar to the experiments Galileo performed. This is the third lesson in a 3 part investigation with pendulums. This lesson is also based on a lesson from the curriculum I use in my classroom- FOSS (Full Option Science System). I use some of their worksheets for recording data, but these graphs can be easily replicated using graph paper and/or drawing.
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:
Planning and Carrying Out Investigations
Students should have opportunities to plan and carry out several different kinds of investigations during their K-12 years. At all levels, they should engage in investigations that range from those structured by the teacher—in order to expose an issue or question that they would be unlikely to explore on their own (e.g., measuring specific properties of materials)— to those that emerge from students’ own questions. (NRC Framework, 2012, p. 61) (5PS2-1)
I have the students get out their Science Notebooks and look at their notes and data from the previous pendulum experiment (Part 2). I ask them if they had any "A-Ha" thoughts about what we did and I have the students share their thoughts. Our discussion includes the idea that only one of the 3 variables that we changed in the previous investigation caused a change in the number of swings. The students tell me that the only variable that changes the number of swings is the length of the pendulum.
I then ask them what the relationship is between the length of the pendulum and the number of swings and they tell me that the longer the string is on the pendulum, the lower the number of swings within a time period (15 seconds). We use this variable since it is the only one that has a different outcome when the variable is changed. (The change in mass and the change of the release points made no difference in the number of swings.)
I tell them that they have previously made a graph representations in the previous lesson- a concrete graph and a picture graph of the pendulums and that today we are going to make a coordinate graph of the variable we tested of the different pendulum lengths. The concrete graph is made by hanging all of the pendulums of different lengths (including the initial pendulums of 38cm in length) under the number of swings that were recorded. This allows for the students to see a visual and concrete representation of the experiment. Here is a student's pendulum picture graph and another student's pendulum picture graph. These worksheets were taken from the curriculum I use- FOSS (Full Option Science System) but can be easily replicated in a drawing or on graph paper.
I explain that we will also be making predictions of how many times a pendulum swings based on the length of the pendulum by using the graph and testing that prediction.
I first distribute graph paper to each student (small grid graph paper works best since there are a lot of data points). i am using graph paper from FOSS (Full Option Science System) which is the curriculum we use for science, but the graph can be done on graph paper as described below:
We create the coordinate graph by drawing and labeling the x-axis and y-axis. I tell the students to use a ruler or straight edge so that their axes are straight. I have them label the x-axis- "Length of pendulum (cm)" and mark off every point by 10 (10, 20, 30, 40, ... until 200). I then have the students label the y-axis "Number of Swings in 15 seconds" and mark every point by 1 (1, 2, 3, ... until 26). I have the students also title the graph: "Pendulum Swings Data".
We then record the data from the previous experiment based on the changing variable of the pendulum lengths. I model for the students how to graph the first few ordered number pairs to make sure they know how to complete the graph. Student pendulum coordinate graph and another student's pendulum coordinate graph.
* The students have had several math lessons learning about graphing ordered numbered pairs, so this activity should be review for them.
When they have finished their graphs, they compare the three graphs- the concrete graph of the pendulums (which is the actual pendulums of different lengths hanging from a number line), the picture graph (these are students' drawings of the concrete graph), and the two-coordinate graph. I ask the students to discuss what the similarities and differences are among these 3 representations and how these are useful. During the discussion, many students notice that the 3 graphs are similar
I then ask the students what a prediction is and I want them to look at their coordinate graph to make a prediction. I ask them to predict how many swings an 80cm length pendulum would make in 15 seconds. I give them about a minute to figure this out and then we share answers. I have them write their prediction at the bottom of their graph using the following sentence frame: I predict that my 80 cm pendulum will swing ___ times in 15 seconds.
After a few minutes of discussion, I give each partnership a new string that is a random length and I tell them to make a new pendulum from this string. They use only 1 penny again for the bob and make sure to release the pendulum from parallel to the floor. I tell the students to make predictions about the new strings they have been given. They test out the new length to show whether they made the correct prediction or not. They trade their strings with another partnership and they do this a few times.
I informally evaluate the students' understanding of the experiments by looking at their graphs and science notebooks as well as listening to their discussions throughout the 3 lessons.