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Lesson: Energy Transfer in Musical Instruments

(Provided courtesy of TeachEngineering.org and © 2004 Engineering K-Ph.D. Program, Pratt School of Engineering, Duke University.)

Level: Grades 5-6
Time required: 1-2 hours
"Alt Saxophone" by Ben Stassen

ABOUT THIS LESSON:

Energy transfer is a central concept in the majority of engineering designs, including designs for musical instruments. In this lesson, students will grasp the concepts of energy and energy transfer, and then apply what they’ve learned by designing and building their own musical instruments.

NATIONAL SCIENCE STANDARDS:

This lesson fits several science standards. A sampling is listed below, but check online for the full list.

North Carolina Science (Grade 6 – 2004)

6.02 Analyze heat flow through materials or across space from warm objects to cooler objects until both objects are at equilibrium.
6.03 Analyze sound as an example that vibrating materials generate waves that transfer energy. Frequency.
6.07 Analyze the Law of Conservation of Energy: Conclude that energy cannot be created or destroyed, but only changed from one form into another.

BACKGROUND:

This lesson teaches students concepts of energy and energy transfer. In a simple sense, examples of objects possessing energy are a car traveling down the highway or a raindrop falling from the sky. These are obvious examples of bodies possessing overall kinetic energy (energy of motion).

In the macroscopic sense, bodies as part of a system can possess overall kinetic energy (energy of motion) or potential energy. Each system also contains a certain amount of internal energy: energy associated with the kinetic and potential energies of the system’s molecules or atoms.

ConvectionWhen a set of objects is defined and contained in an environment, this set of objects is defined as a system. For instance, a hot pot of water is a system and a room is an environment. The bodies within the system contain a certain amount of energy initially, whether it be overall kinetic or potential energy or microscopic kinetic or potential energy (internal energy). There are two ways that a system can exchange energy with its environment: work done by its environment and heat.

In terms of heat, the system originally contains a certain amount of internal energy due to the vibration of its molecules. When the system is originally at a different temperature than its environment, energy will be transferred (heat) between the system and its environment until the system and its environment are at the same temperature, whereby thermal equilibrium is established.

The other way energy is exchanged is by external work, or work done by the environment. A simple example of this is a block that is initially resting on the ground. Upon application of a large enough upward force by the hand of a person, the block will be lifted a certain distance. Energy is thus transferred from the person (environment) to the block (system). The environment gave up some energy, and the system accepted the energy.

Learning Objectives

At the end of this lesson, the student should be able to:
  • define energy, heat, energy transfer, work, and thermal equilibrium
  • state how to utilize the concept of energy transfer to make a musical instrument
  • state the law of conservation of energy
  • define a system and environment in terms of energy, and describe how energy transfer occurs between the two

LESSON:

Begin the lesson by taking a rubber band. Stretch the rubber band and release. Explain to the students that the transfer of energy from potential energy in the stretched rubber band to kinetic energy in the flying rubber band is responsible for the rubber band flying across the room. Ask the students to explain the energy transfer mechanisms associated with the rubber band flying across the room.

The students should be able to accurately explain why the rubber band is flying across the room. The hand performs work on the rubber band, and in the stretched position, the rubber band has a certain amount of potential energy. Upon release, that potential energy is converted into kinetic energy. Hence, the rubber band goes flying through the air.

Ask the students what will happen to an extremely hot pot of water if kept in the room at room temperature for a long time. Hopefully, they will say that it will cool down over time, that if enough time has passed, one will be able to put his or her hand in the pot. The reason the water in the pot cools down over time is due to energy transfer in the form of heat being transferred from the warm object (water) to the cooler object (room) until eventually they reach the same temperature. This is a naturally occurring example of energy transfer. The musical instrument activity shows how musical instruments have been engineered to produce beautiful music using energy transfer.

VOCABULARY:

Work – the application of a force on a body that transfers energy to that body
Energy – the capacity or ability to do work
Internal Energy – all the energy of a system that is associated with its microscopic components: atoms and molecules
Heat – the transfer of energy from one object to another due to temperature differences
Thermal Equilibrium – the situation in which two objects in thermal contact cease to exchange energy by the process of heat; i.e. they are at the same temperature
Kinetic Energy – the energy an object has because it is moving
Potential Energy – the energy an object has because of its position or condition, rather than motion. A raised weight, coiled spring, or charged battery all have potential energy
Music – vocal or instrumental sounds possessing a degree of melody, harmony, or rhythm
Tone – a sound of distinct pitch, quality, and duration; a note
Vibration – a rapid linear motion of a particle or of an elastic solid about an equilibrium

ACTIVITY – Energetic Musical Instruments:

Britannica_Cornet_B♭_with_Enharmonic_Valves

Before the activity, students should understand the methods of energy transfer and be able to describe energy transfer in the context of a system.

Materials List

Each group of two should receive at least…
* 1 soap dish (no lid necessary)
* 1 plastic bowl
* 3 rubber bands of different thicknesses
* Either a shoe box of any size or a toothbrush
* Either a pint sized drinking glass or a 8.5” x 11″ notepad
* A pencil, tape, and scissors
* Springs (approximately 2-3 inches long)
* Optional: whatever other supplies may be used for construction of an instrument

Introduction

Students learn to apply the principles and concepts associated with energy and the transfer of energy in an engineering context through the designing and making of a musical instrument. The students must choose from a variety of supplies presented to them to make an instrument capable of producing three different tones. After the accomplishment of the design, students must explain the energy transfer mechanism in sufficient detail and describe how they could make their instruments better.

Ask students, “Have you ever wondered how an acoustic guitar produces the amazing sound we hear? How neat would it be to go home and tell your parents you made a musical instrument in school today?” The truth is that the acoustic guitar utilizes principles of energy transfer to produce the sound we hear.

The engineering profession is about applying scientific concepts to produce things of use. Making an instrument based on energy transfer is a perfect example of this. Providing young students with the foundation of engineering that this activity will help to provide is extremely valuable to them.

Procedure

Lay all of the supplies out in the front of the classroom and explain to students that a musical instrument must be built that is capable of producing three different tones from the provided supplies.

Let each team meet for 5-10 minutes and brainstorm possible ideas for their designs (ideas could range from plucking the rubber bands over soap dishes to using pencils to hit notepads). Let two teams at a time take their supplies.

During the activity, the teacher can be walking around helping students by asking questions such as “How might these supplies be used to create sound?” Students should be able to come up with solutions to this problem on their own, but they may need help to better understand the problem. If students do not know what to do, help them understand the problem rather than doing it for them.

Let the students design their instruments. Estimating the time is difficult because groups will finish at different times, so be flexible. 30 minutes is reasonable. If certain groups finish quickly, have them design another instrument using different materials.

After their instruments are designed, each group must write down an explanation of the energy transfer mechanisms involved. Each team must present and explain their instrument in front of the class and describe how they could make their instruments better.

Example

The most common type of design generally features rubber bands wrapped around a soap dish. By plucking a rubber band, the band is given a certain amount of potential energy transferred to it by the finger that performs work upon the band. Upon release, the band begins vibrating, and energy from the vibration will be transferred to the soap dish. Altogether, the vibration of the soap dish and rubber band will be heard as sound, which carries energy, and the hollowness of the soap dish will serve to amplify the sound.

Investigating Questions

* Why do some of the designed instruments sound louder than others?
* For students wrapping rubber bands around a 6-faced cardboard box, ask them how they think the sound would change if they cut a hole in the box. Does this change remind them of any familiar instruments?
* How many different energy transfer processes occur within each instrument? For instance, rubber bands over a drinking glass involves the hand imparting energy to the rubber band and upon vibration the energy of the rubber band gets transferred to the glass which also begins to vibrate.

Tips

Ensure that students use rubber bands and scissors in an appropriate manner. If students are having difficulty brainstorming ideas, remind them to think of how guitars and violins work.

Assessment

Did students’ instruments produce three different tones? Were students able to explain the functioning of their instruments well?

Activity Extension

Challenge the students to investigate and research a musical instrument and write a one-page paper describing how that instrument works. Challenge them to find more supplies around the house that could be used to make a musical instrument capable of producing different tones.

ADDITIONAL DEMONSTRATIONS:

Take a tennis ball (or some other ball) and drop it from the height of your nose. The ball will not bounce as high as it was dropped. Ask the students to explain why. The explanation should go as follows: the ball has a certain amount of energy as it is falling down and upon collision, the ball deforms, which increases the internal energy of the air inside the ball, and by the conservation of energy, this decreases the kinetic energy of the ball causing it not to bounce up to its original height. Also, friction between the ball and the air causes the kinetic energy of the ball to be converted into heat. The force acting against the ball while it is in air is known as air resistance or drag.

Hit a metal pan with a metal spoon. The students should be able to explain that the kinetic energy of the spoon transfers energy to the metal pan, which begins vibrating. Meanwhile, sound is produced from the collision that carries with it energy. The students should be able to explain that some of the original kinetic energy of the spoon went into vibration of the metal pan and some of it went into sound upon collision. This demonstration can involve hitting any two objects together that will make noise.

CONTIBUTORS:

Adam Kempton, Lesson creator/editor, Duke University, Pratt School of Engineering

Alt Saxophone” by Ben Stassen (Flickr Commons)
Convection” by Oni Lukos (Wikipedia Commons)
Britannica Cornet B♭ with Enharmonic Valves” by Encyclopædia Britannica (Public Domain)

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