Topic Potential and kinetic energy Key Question How does a paper model of a jumping frog illustrate the conversion of elastic potential energy to kinetic energy to gravitational potential energy? Learning Goals Students will: measure the height and horizontal distances paper frogs can jump when folded from different materials, and analyze and describe a frog jump in terms of its potential and kinetic energy. Guiding Documents Project 2061 Benchmark Energy appears in different forms. Heat energy is in the disorderly motion of molecules and in radiation; chemical energy is in the arrangement of atoms; mechanical energy is in moving bodies or in elastically distorted shapes; and electrical energy is in the attraction or repulsion between charges. NRC Standard Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways. Math Measurement linear Science Physical science potential energy gravitational elastic kinetic energy Integrated Processes Observing Comparing and contrasting Collecting and recording data Analyzing Materials Copy paper (20 lb) Card stock (65-95 lb) Scissors Overhead transparencies Meter tapes Safety goggles Background Information In this activity, students fold a paper frog that can be made to jump into the air. The jumping paper frog is used to illustrate three forms of mechanical energy and the conversions that occur between these forms as the frog leaps into the air and falls back to the ground. Mechanical energy is the energy associated with the motion, position, or deformation of material objects. The energy a material object possesses because it is moving is called kinetic energy. The energy associated with the position of an object is called potential energy. Changing the position of an object in a gravitational field changes the potential energy of the object. The energy associated with an object when the object is deformed (stretched or compressed) is called elastic potential energy. To observe deformational mechanical energy, simply stretch a rubber band or compress a spring. Folding and playing with a jumping paper frog is a simple way for students to observe these energies and think about how one form of energy is converted into another form of energy. Relative to the surface the frog is sitting on, the mechanical energy of the frog is zero. Pressing down on the back of the frog increases the elastic potential energy of the frog because the paper is deformed into a different shape. When the finger is quickly removed from the back of the frog, the elastic potential energy stored in the bent legs is converted to the kinetic energy evident in the moving. kinetic energy gravitational potential energy kinetic energy elastic potential energy 38 FALL 2009 AIMS Education Foundation
As the frog rises, its kinetic energy decreases, but its gravitational potential energy increases. At the top of the frog s jump, for an instant, the frog is motionless. At this point, the frog s kinetic energy has all been spent to move the frog to its maximum height. At this maximum height, the gravitational potential energy is also at a maximum. Since the frog is unsupported, it starts to fall. Falling is a form of motion, so the kinetic energy of the frog increases at the expense of its gravitational potential energy until the frog comes to rest on the other lily pad. Key Vocabulary Gravitational potential energy: the energy associated with the position of an object in a gravitational field Elastic potential energy: the energy associated with an object when the object is stretched or compressed Kinetic energy: the energy associated with a moving object Mechanical energy: the energy associated with the motion, position, and deformation of material objects Management 1. Plan to display the science information pages using a projection device. 2. Copy the Frog Folders page onto green copy paper and green card stock (65 pound or greater). Make enough copies on both kinds of paper so that every student can have one frog of each kind. 3. Copy the Frog Fillers page on transparency film so that each student can have one rectangle. 4. Each group will need one copy of the Folding a Jumping Frog page. 5. Have safety goggles for each student. Procedure 1. Use the first science information page to introduce or review the concepts of elastic potential energy, gravitational potential energy, and kinetic energy. 2. Ask the Key Question and state the Learning Goals. 3. Have students get into groups of two or three. Distribute a paper frog to each student and a page of folding instructions to each group. 4. Guide the students through the steps used in folding a paper frog. Have a few extra paper frogs on hand in case any students make errors. 5. Instruct the students to place the jumping frog on a flat surface with the face of the frog directed away from their faces. 6. Direct the students to push down on the back of the frog with a fingertip and quickly slide the finger to the rear and off the back of the frog. Inform them that the frog should jump up and away in the direction it is facing. Tell the students not to be concerned if the frog jumps only an inch or two into the air. Folded copy paper stores very little elastic potential energy. push down on frog 7. Ask how students could quantify the heights and distances jumped by their frogs. Discuss the variables that would need to be kept consistent (jump surface, location on the frog from which measurements are taken, etc.) and the techniques that could be employed to ensure valid comparisons among groups. 8. When students have agreed on techniques, distribute meter tapes, safety goggles, and the student page. 9. Have the students perform multiple trials and measure and record the best height and distance their copy paper frogs can jump. 10. Distribute a paper frog copied on card stock to each student. 11. Have students fold the frogs and repeat the process of measuring and recording the best height and distance data. 12. Distribute an overhead transparency rectangle to every student. Show the students how to unfold the card stock frog and insert the plastic strip. unfold frog quickly release insert transparency rectangle 13. Have the students measure and record the best height and distance the plastic-energized frogs can jump. 14. When students have had time to respond to the final question on the student page, display the second science information page and discuss students responses and what they learned. Connecting Learning 1. What are the kinds of potential energy that your frogs had in this lesson? [gravitational potential energy, elastic potential energy] AIMS Education Foundation FALL 2009 39
2. What are some other examples of things that have elastic potential energy? [the spring in a retractable ballpoint pen, a slingshot, a bow, a catapult, etc.] gravitational potential energy? [water at the top of a waterfall, a skateboard at the top of a half-pipe, a piece of fruit on a tree, etc.] 3. What is kinetic energy? [the energy of motion] What are some examples of things that have kinetic energy? [a ball in motion, a moving car, a moving bicycle, etc.] 4. How high and how far did the frog you folded out of paper jump? How did this compare to the distances jumped by the frogs of others in the class? What might be some reasons for any differences? 5. How high and far did the frog you folded out of card stock jump? How did this compare to the distances jumped by the frogs of others in the class? What might be some reasons for any differences? 6. What happened when you put the plastic inside the card stock frog? [The frog jumped higher and farther.] Why did this happen? [The transparency film gave the frog more elastic potential energy to be converted into kinetic energy.] 7. What do you think would happen if you put the transparency film in the paper frog? Explain. 8. At what point did the frog have the most gravitational potential energy? [at the top of its jump] Why? 9. When did the frog have the most elastic potential energy? [before it was released to jump] Why? 10. When did the frog have kinetic energy? [when it was moving] When was there no kinetic energy? [when it was at rest] 11. What are you wondering now? 40 FALL 2009 AIMS Education Foundation
Key Question How does a paper model of a jumping frog illustrate the conversion of elastic potential energy to kinetic energy to gravitational potential energy? Learning Goals Students will: measure the height and horizontal distances paper frogs can jump when folded from different materials, and analyze and describe a frog jump in terms of its potential and kinetic energy. AIMS Education Foundation FALL 2009 41
Science Information Mechanical energy is the energy associated with the motion, position, or deformation of material objects. Gravitational potential energy is the energy associated with the position of an object. A boulder at the top of a hill has gravitational potential energy. Elastic potential energy is the energy associated with the compression or extension of an elastic (spring-like) object. A compressed spring and a stretched rubber band have elastic potential energy. compressed rubber band spring stretched Kinetic energy is the energy associated with the motion of an object. A football player running down the field has kinetic energy. 42 FALL 2009 AIMS Education Foundation
gravitational potential energy Science Information kinetic energy kinetic energy elastic potential energy AIMS Education Foundation FALL 2009 43
3 ½" by 2" 1. Fold corner. 2. Open and fold over other corner. 3. Open and identify where the crease lines intersect. 4. Fold over at the intersection point. 5. Open and fold over in the opposite direction. 6. Pinch the sides, along crease lines, in toward the center of the figure. 7. Press down the top triangle. 8. Fold up corner of top triangle to form a front leg. 9. Fold up the other corner to form the second front leg. 10. Fold both legs up, out of the way. 11. Fold side over to centerline of figure. 12. Fold other side to centerline of figure. 13. Fold down both legs. 14. Fold down the head. 15. Fold the rear legs back, under the frog. 44 FALL 2009 AIMS Education Foundation
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1. Fold one jumping frog out of paper and one out of card stock. 2. Measure and record the best height and distance each jumped. 3. Insert the plastic strip inside the card stock frog. Measure and record the best height and distance it jumped. Height Jumped Distance Jumped Paper Frog Card Stock Frog Plastic Strip Frog 4. Use the energy terms, elastic potential energy, gravitational potential energy, and kinetic energy to describe the jump of a frog from one lily pad to another lily pad. AIMS Education Foundation FALL 2009 47
Connecting Learning CONNECTING CONNECTING LEARNING LEARNING 1. What are the kinds of potential energy that your frogs had in this lesson? 2. What are some other examples of things that have elastic potential energy? gravitational potential energy? 3. What is kinetic energy? What are some examples of things that have kinetic energy? 4. How high and how far did the frog you folded out of paper jump? How did this compare to the distances jumped by the frogs of others in the class? What might be some reasons for anydifferences? 48 FALL 2009 AIMS Education Foundation
Connecting Learning CONNECTING CONNECTING LEARNING LEARNING 5. How high and far did the frog you folded out of card stock jump? How did this compare to the distances jumped by the frogs of others in the class? What might be some reasons for anydifferences? 6. What happened when you put the plastic inside the card stock frog? Why did this happen? 7. What do you think would happen if you put the transparency film in the paper frog? Explain. 8. At what point did the frog have the mostgravitational potential energy? Why? AIMS Education Foundation FALL 2009 49
Connecting Learning CONNECTING CONNECTING LEARNING LEARNING 9. When did the frog have the most elastic potential energy? Why? 10. When did the frog have kinetic energy? When was there no kinetic energy? 11. What are you wondering now? 50 FALL 2009 AIMS Education Foundation
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