Free Fall Lab, Day #2

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Objective

Students will be able to state the value of the acceleration due to gravity in meters per second squared and use it in mathematical models in situations of free fall.

Big Idea

Students conclude that the acceleration due to gravity is 9.8 meters per second squared.

Free Fall Stations

40 minutes

The goal of this lesson is to expose students to multiple situations that have objects in free fall so that as a class we can have a discussion afterwards about the nature of objects in free fall and discover the acceleration due to gravity on Earth. At each station, I ask students to use different skills including: calculating acceleration of objects, calculating the time objects are in the air, or analyzing data collected via data table or graphs to collect acceleration of the object. After all of the students have been through the lab stations, they place their accelerations they determined from their data into a large class data table that we use for discussion on what free fall is. 

To start out class, I ask students to remind me what they started the day before because students have already completed one station in the Free Fall Stations Lab. After students have given me an idea of what they will be doing in class today for the lab section of class, I ask them to think about what station they did yesterday. Today they start at the next station. When all groups know what station they will be at, I ask them to move to that station an begin. They get 8 minutes at each station before they rotate to the next station. While students are working, I walk around to answer any questions they may have and to make sure each group is following directions and staying on task.

               

Post-Lab Free Fall Discussion

20 minutes

After all groups have finished the lab, I give them 5-7 minutes to ensure that their calculations are complete. As groups wrap up their work, they post their the accelerations data from stations #3, 4, and 5 on the board in a class data table as shown below. When all groups have added their results on the board, we begin our post-lab discussion.

 

I start out the post-lab discussion with helping students identify what free fall is by asking them "What did you see in common with all of the stations?". Students raise their hands and I call on them to answer until I get what I am looking for which is that objects are all falling through the air. We then define free fall as occurring when an object falls with only force of gravity acting on it. I go through each station and ask them to define what object was in free fall in each case to make sure that they can identify an object in free fall in a real-life situation.

After reviewing the concept of free fall, students shift their attention to the class data table, shown above. I ask them to look at all of the data in all of the columns and see what number they would guess the acceleration would be when objects are in free fall. Based on the data, students can say it is somewhere between 8-10 meters per second squared. I tell them that the acceleration due to gravity is 9.8 meters per second squared on Earth which is close to what the "average" of their data would be. I make sure to tell them that each planet has a different acceleration due to gravity. So if we were on the moon, they would have calculated about 1.6 meters per second squared for the acceleration due to gravity.

Quiz Reflection

10 minutes

After we have finished our discussion on free fall, I pass back the quizzes that the students took in the previous class. I like to do this so that students can finish the activity that they started the previous day before switching to a reflection over the quiz. Before I hand the quizzes back to students, I tell them the overall successes and mistakes of the class so they know what was common for many students. Then I hand the quizzes back and ask them to look through the notes I made on their quizzes and what they needed to fix for next time. In this reflection time I do not give them any specific questions to answer; I just want them to look at their mistakes and ask questions about them. I do allow retakes so after their reflection time, I pass out the Additional Practice Worksheet for students to complete prior to retaking the quiz. It is optional for them to take the worksheet but about half my students take it just for the extra practice.