Potential and Kinetic Energy

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Objective

SWBAT differentiate between kinetic and potential energy and how magnetic potential energy is transferred to kinetic energy.

Big Idea

How can potential energy be realized in magnets? Help your students understand potential and kinetic energy using magnets.

Preface

5 minutes

If you have been a science teacher for a year or two, you’ve likely read hundreds of lesson about how to teach Potential vs. Kinetic Energy. The truth is that you have got to find the one you like best and stick with the strategies that help students learn. I’ve learned a few important strategies. Strategy #1: Tie in something emotional and help the students discover the phenomena. In the Engage Section of this lesson, I use an Angry bird doll and a toy truck in an effort to help the students create a definition kinetic and potential energy.  I still have adults coming back to visit asking if I still use the same truck. Strategy #2 : Let the kids create the investigation. Show them all of the materials and ask, “How can we test what we just discovered using this stuff?” Physics is familiar to students and with a little prompting, they can determine how to create a great investigation. In the Explore Section, I explain how students create an investigation with magnets. Strategy #3: Use Common Core Writing Standards to evaluate. It doesn’t have to be a 5 paragraph essay. Simply have the students write a three-sentence summary. I have found summary writing has elevated my student learning and it is easier to grade. In the Evaluate Section, I students write a one-sentence summary answering the question, "How can scientists and engineers use our data?" 

Finally, this lesson is one of my keystone lessons for the engineering design process. Mechanical engineering is about energy and energy transfers. A great lesson in which the kids learn and remember is the building block for further successes. If you are interested in an engineering design process lesson, check out my Designing a Roller Coaster and Exploring Magnetic Levitation lessons. 

Engage

15 minutes

To begin my strategy is Demonstrating Science Content.  I use toy props to develop a classroom culture where students engage in meaningful and productive scientific discourse with peers. I like to use toys because they bring a sense of fun and joy to the classroom. I use a rubber band, a Truck and an Angry Bird stuffed toy.

It is important to begin with a pre-assessment so I know what students already know, understand, and misunderstand. My strategy is an Exit Slip format. I ask the question, "What is the difference between potential and kinetic energy?"

To differentiate, I give the students who know the terms the opportunity to help me with my demonstrations. My strategy is to assess their understanding as they generalize to an activity. The demonstrations are usually very fun and the differentiated students like to be a part of them. An important component of the demonstration is the exploration of phenomena. I expect the students to watch, think, and come up with ideas as to how kinetic and potential energy are different. 

Kinetic/Potential Energy Demonstrations

  • I push Chuck the truck. 
  • I let a rubber band go.
  • I throw the Angry Bird. 

I ask if Chuck the truck has energy. Several students indicate that he does, I explain, "Then he can move by himself." I call the truck as if it were a dog and it doesn't move so we conclude the truck does not have energy. I ask, "How can Chuck get energy?" The students reply, "By pushing him." I explain how that is the energy of movement or kinetic energy. I hand out rubber bands and ask each student to shoot at the ceiling and demonstrate kinetic energy. We throw the Angry Bird toy to one another with different amounts of kinetic energy.  

I change the position of the Chuck from the center of the table to the end of the table. I ask, "Now does Chuck have energy?" The students say no having just been through the demonstration. I explain that I don't want to break Chuck so the Angry Bird will help.

I place the Angry Bird on the edge of the table. I explain -- if he can move by himself, he has energy. I let him go and the toy drops to the floor. I ask, "Did he have energy?" The students indicate yes and I ask, "Why?" We discuss the force of gravity. I explain the energy is being stored  and it is called potential energy. I ask, "What changed?" We discuss how the position on the table changed the energy, not the toy.

I throw a flaccid rubber band at a student and ask if it hurt them. I then pull back the rubber band and ask why they flinched. I explain that elastic potential energy is energy stored when I pull back the rubber band. I then ask, "What changed?" Again we discuss the position of the rubber band before and after I pulled it back. I explain that potential energy is energy stored by gravity and in elastic. In addition, magnets have potential energy. 

After the demonstrations, student return to their seats and respond to the same Exit Slip question, "What is the difference between kinetic and potential energy?"

My strategy is to get immediate feedback about student learning. I can determine who needs additional help so I can work with them individually later in the lesson. 

Explore

40 minutes

To help them understand potential energy, my strategy is to Create an Investigation.

I introduce a lab with the intention to build background knowledge and to create experiences with magnets. The students explore the transfer of potential and kinetic energy using magnets. There are two components to the lab,

  • Experiment #1: The Attracting Magnets
  • Experiment #2: The Repelling Magnets.

As a class we plan and design an investigation. 

I show students the magnet we will be using and the nail. Students pose testable questions and we determine how to answer the question, What is magnetic potential energy?

I work with my students to identify independent and dependent variables and controls. The class discusses how to gather information as well as how we should measure and record the data. I ask students to think about how many trials are needed to support a claim. 

Data is collected in tables and students draw models of the movement of the magnets. 

Students draw a ruler and show how the two magnets interact recording the distance when there is no attraction/replusion and the distance at which the potential energy kicks in to attract or repel. Check out my Student Demonstration Movie

 

Below is an example of the Magnet Lab

1. Place the square magnet 10 cm away from the nail. Move the nail without touching the nail. Determine 5 distances and record an observation of the nail at each distance. 

Repeat this lab using two magnets at opposite poles.  Draw a model of your data below.

  

Explain

15 minutes

Collecting data is not the end goal. Students must be able to explain what the data means. My strategy is to use student reflections to assess understandings of the content.

I ask students to respond to the following questions.

  1. Explain how distance has an effect on the potential energy of the magnet.  
  2. To promote using precise vocabulary, I ask students to use the words attract, repel, potential energy, stored, and distance. 

 

Evaluate

15 minutes

My strategy for evaluation includes an analysis of the attractive and repelling forces. I ask students to respond to the following prompts.

 "Attraction/ Repelling: which is a more effective transfer and why?:  

"How did the nail and the other magnets move?" 

My final assessment strategy is to connect learning to the real world by writing to learn. I ask the students to write a one-sentence summary answering the prompt,  "How can engineers use our data?"

If you are interested in a more thorough lesson testing a magnetic levitation train model, check out my lesson called Exploring Magnetic Levitation.