The Impulse of Bungee Jumping
Lesson 3 of 9
Objective: Students will be able to compare change in momentum with impulse.
During the previous lesson, students were introduced to impulse and it's relationship to change in momentum. The goal for today's lesson is to apply that understanding of the impulse-momentum relationship (HS-PS2-2) in a lab activity. Specifically, students will use stuffed animals as bungee jumpers (SP2) and then measure the relationship between impulse and the change in momentum (SP3-SP5 & SP8). I start the class with an attention-grabbing video before moving into the actual lab activity. Today's lesson ends with students sharing one word to summarize their lab experiences.
This lab requires the following materials for each group: ring stand, 5-10 rubber bands, stuffed animal, and a dual-range force sensor.
As soon as students come into the room and are seated, I play this video to pique the students' interests about bungee jumping. The goal is to get students engaged by thinking about springs and changes in momentum before they jump into today's lab activity. The video provides students with a great overview on the physics concepts students will need, along with a little humor. Because students are going to be active for the majority of today's class, I don't worry much about this introduction being passive.
Because my students are so responsible, I allow them freedom in choosing lab partners for today's activity. Groups of three seem to work best for the lab so one student can operate the computer while the other 2 students focus on releasing the bungee jumper. After they've chosen their groups, someone from each group needs to get a copy of the lab, force sensor, ring stand, and set of rubber bands.
The purpose of this lab activity is to get students to see that impulse and change in momentum are equivalent. Students create a bungee cord out of rubber bands and attach one end of the cord to the force sensor while the other end is attached to a stuffed animal. I asked students during a previous class to bring in a stuffed animal from home, so we have a wide variety of jumpers in the classroom. My students have used Logger Pro since freshmen year, so they have no problems connecting the force sensor to a computer. Once the set-up is complete, students are ready to let their stuffed animals go for a jump!
The procedure in the lab document is non-existent so that it satisfies the requirements of an AP Physics 1 inquiry lab. Students start by creating their bungee jumping apparatus using the rubber bands, ring stand, and force sensor. Once they have a working jump station, students release their stuffed animal and measure the instantaneous force. Not only do the students record the instantaneous force, but they also analyze the graph produced by the Labquest. After completing several trials, students find the average starting and stopping forces along with the average time it took the stuffed animal to reach the bottom of its fall. With this data, students are then able to calculate the impulse of their bungee jumper and compare the accuracy of their calculation with the jumper's change in momentum.
I make sure to circulate throughout the room and answer needed questions throughout the work time, but I'm also careful to not explicitly tell students what they need to do. Once students have completed collecting data, they are familiar with the expectation that any remaining time should be used to complete a formal lab report.
When there is approximately 10 minutes prior to the end of class (5 minutes left of the time I've allowed for this activity), I ask students to put everything back the way they found it and return to their seats. I also tell them at this point that the lab is due one week from this class.
One Word Closure
To bring closure to our class today, students need to think of one word that they'd use to describe their thoughts on the bungee lab. Once a word is used by a student, it cannot be repeated. After I give them the instructions, students get about 30 seconds to think of their word. Then, we go around the room and share our words! I usually model the activity by being the first person to share a word, and then turn to the student closest to me to share next. We go up and down the rows until everyone has had the chance to contribute.
As students are sharing their words, I'm making mental notes on the overall tone of their comments. Are students excited and joking? Or, are the students monotone and overwhelmed? Listening to students as they share gives me insight into how the lab went and if I need to make any adjustments. Also, if a word strikes me as being completely out of context, I do ask the student to clarify!
The sample words from today's lab show me that the majority of students enjoyed the lab. There were a few words such as "whatever" that show indifference and lack-luster feelings about the activity, but overall the students offered positive feedback. Reviewing these words, along with my informal observations and conversations that took place during the lab time, tells me that the lab is meaningful and I really don't need to make adjustments before repeating the activity next year.