The Power of Oreos
Lesson 8 of 10
Objective: Students will define and calculate power.
Throughout this unit, students have grasped an understanding of the conservation of mechanical energy. Thus, the goal for today's lesson is to connect energy to power (HS-PS3-3). Specifically, students will examine the calorie content of Oreos to explore the relationship between work, energy, and power (SP3 & SP5). I start the class by asking students to show what they know before introducing the concept of power. Today's lesson ends with the Oreo activity.
Providing students with Oreos for the activity is optional.
Show What You Know
Today's class starts off with students showing what they know. I have the word "power" written on the front board and have students pick up a blank piece of paper as they enter the room. Once the bell has rung, I ask students to write down anything and everything they know about power. They should be working on this individually, as I'm using it as way to assess any prior knowledge.
Once the full 5 minutes has passed, I choose a student to share an idea from his paper. I usually pick the student closest to me, and after he's shared I write his idea down on that front board. We then go around the room and students continue to share, but once a contribution has been recorded it cannot be repeated. This process continues until all ideas have been shared. I leave our example on the board in the hopes that we'll refer back to it throughout today's class.
While students are sharing their ideas, I am internalizing the information they are contributing. Looking at how much, or how little, they know helps me to adjust my pacing and depth for today's class. I'm also trying to identify any misconceptions that were shared so that I can be sure to address and correct those.
It's time for students to take out their science notebooks and get ready to learn the fundamentals of power. My students are operating under the expectation that they must write down key points from the presentation and we work through several examples that also need to be recorded. This expectation of how to take notes has been outlined and ingrained in their learning since freshman year, but we've practiced it quite a bit throughout earlier lessons in the course as well.
I display my PowerPoint (also available as a PDF) to help the students understand what they need to write down, but I also have a hard copy of the document in my hand. The printed copy includes notes (viewable only when the file is downloaded) that I've written to myself to make sure I accomplish the learning goals as we work through the presentation. The nice thing about having a hard copy in my hand is that if I'm teaching and think of a great side-note or new example, I have the ability to write it down immediately.
The presentation starts by defining power both quantitatively and qualitatively. Then, students are acquainted with the units of power and how power is delivered to our homes and schools. Finally, students work through two practice problems that require them to apply both forms of the power equation (P = W/t and P = Fv). After I read the practice problem, students get about two minutes to work on the problem individually or with those seated around them before I work out the solution on the front board.
While I describe this section as "direct instruction," I usually have a lot of interaction with my students throughout the presentation. I am constantly moving throughout the room to change my proximity and am listening to my students as they work through the examples with the people around them. The students will ask questions, participate in problem-solving, and connect to real-world examples to stay engaged the entire time.
For today's closure students need to pick a friend or two to work with, even though each student will do his or her own work. After students have relocated to sit next to the people they chose to work with, someone from each group needs to get a copy of the lab from the front of the room.
The procedure in the lab document is purposely vague because students must think about how to best collect their own data. The purpose of the lab is to emphasize the time component of power, so students are exploring how their power output changes as the time it takes to climb a flight of stairs varies. In order to do this, students must use their weight and the vertical distance climbed to calculate work, and time how long it takes them to climb the stairs. While this is a rather rudimentary way to calculate power, especially since we are ignoring any horizontal displacement, students always enjoy seeing power outputs that are individualized. I also find that any time I incorporate food into a lesson, the material becomes much more meaningful.
Because this lab requires a flight of stairs, we go just outside of the room to an indoor flight of stairs that is not near any classrooms. I purposely pick these stairs so that we don't disturb any other classes. I also give my students a strict warning about the need to be careful while climbing stairs and suggest that each individual thinks about the shoes he's wearing. As students are completing the lab, I move up and down the stairwell to check for hazards and offer feedback on the data collection process. Students understand the expectation that once they have completed collecting the data it's time to organize their work, complete their individual calculations, and decide if the extra steps are worth eating a Double Stuf Oreo.
Students are meant to finish the lab in class, so after they have collected the data and we return to the classroom, I offer students both a double-stuffed and classic Oreo. Of course, I do not mandate that students eat the cookie, but it makes the calculation portion of the lab more fun if students can eat as they work.