How Does Sound Travel Through Air When a Student Taps His Pencil on a Desk

Activeness Blazon:

Belting Out A Physics Lesson

High school science instructor Sam Terfa wanted to demonstrate a fundamental physics principle: resonant frequency. To do so, he found the all-time vocalist at Minnehaha Academy and had him serenade a wine glass. It did non turn out well for the glass.

Grade Level: 6th – 8th form
Subject Thing: Physical Scientific discipline
National Standards: NS.5-8.1, NS.v-8.two

Overview

Sound is all effectually us. Everything we hear in our solar day-to-solar day lives has a distinctive sound, from the jingling of keys to the borer of footsteps in a hallway. Sound is created when objects vibrate. These vibrations cause the air effectually them to vibrate, sending sound waves in various directions. Some objects tend to vibrate at a specific rate. This is known as their resonant frequency.

In this activity, students will explore the vibrating nature of audio and how it travels from molecule to molecule. Students will experiment with how audio waves or vibrations tin be observed, and will compare and contrast the speed of sound through different media. Students also will investigate the resonant frequency of different prophylactic bands, and how that frequency is affected by diverse factors.

Activity Materials

Ping-pong ball
Cord
Record
Paper clip
Tuning Fork – Online sources for tuning forks (price range: $10 – $20: www.carolina.com , www.fishersci.com , www.sciencekit.com)
Rubber bands in various sizes
Marking
Shoebox or tissue

Vocabulary

Medium – (plural: media) the cloth (solid, liquid, or gas) through which sound waves travel.
Frequency – the number of vibrations a sound wave produces each second.
Pitch – the highness or lowness of a sound.
Resonant frequency – an object'southward natural frequency of vibration, every bit determined by its physical properties.

What To Practise

1. Begin the lesson past having students watch the Science Friday Video, "Belting out a Physics Lesson." Discuss with students what they know near sound and how sound travels to our ears. Tell students that they will conduct three sound related experiments to learn more near the nature of audio and vibrations.

Activity 1

1. Tell students that sounds are caused when an object vibrates. Vibrations travel in the grade of invisible audio waves. Ask students if they tin can think of ways that we can observe vibrations and their effects on other objects.

2. Have students tape a slice of string to a ping-pong ball so tape the other side of the cord to the edge of a tabular array so that the ping-pong ball hangs freely. Tell students that they are going to gently strike the tuning fork, and then slowly bring the tuning fork near the ping-pong ball. Ask students to explain why the ping-pong ball jumped when gently tapped by the tuning fork.

Activeness 2

1. Ask students if they think sound travels more than easily through a solid or a gas. Pair the students into teams of ii. Designate 1 student every bit the "listener" and the other student as the "sound-maker".

2. Accept the audio-maker drop a paper clip on the table while the listener faces in the opposite direction. Is the sound easy to hear?

3. Have the listener press one ear confronting the table while roofing the other ear. Have the audio-maker drop the paper clip on the table. Was the sound easier to hear every bit information technology traveled through the tabular array?

4. Echo the same activity using the tuning fork instead of the newspaper clip. Instead of dropping the tuning fork on the floor, accept students strike the tuning fork and hold it in their hand. Talk over with students the differences heard by using the tuning fork instead of the paper clip.

5. Have the students substitution roles and echo steps 2 through 4. Have students discuss which was easier to hear and why.

Activity 3

1. Review with students the definition of pitch and resonant frequency. Have students utilise their own voices to give examples of a high-pitched voice and a depression-pitched voice.

2. Have students stretch three condom bands of varying widths around a shoebox or tissue box with the elastic over the opening. Use the mark to label each rubber band as "A", "B" or "C". If there is not enough space on the rubber band, label the side of the box adjacent to the corresponding prophylactic band.

3. Take students create a chart with three rows (labeled rubber band A, B, and C) and 3 columns (labeled width measurement, predictions and results). In the width column, have the students measure and record the width of each condom ring. In the prediction column, have students number which safe band they think will accept the highest pitch and which volition have the everyman pitch, with i being the highest pitch and 2 being the everyman pitch. Accept students talk over their predictions.

4. Have students pluck each of the rubber bands and advisedly mind to the sounds produced. Have students record their final results on their chart. Inquire students to compare and contrast their results. Why did each rubber band make a different sound? Did they observe any differences in the vibrations of the safety bands? What are some factors that might bear on the sounds produced by a particular rubber ring? (e.g.,tension, thickness, material, etc.)

What's Happening?

Sound is a type of energy fabricated by vibrations. When an object vibrates, information technology causes motion in the molecules all around it. These vibrations can be passed on to the surrounding air molecules, causing them to vibrate, too. This is how vibrations travel in the form of invisible sound waves. Even though we cannot meet vibrations, we can feel them or see their upshot on other objects. Striking a tuning fork will cause the tips of the tuning fork to vibrate hundreds of times every second. These vibrations will crusade the ping-pong ball to spring when gently touched by the tuning fork.

Sound too tin can travel at different speeds through different media. Vibrations are able to travel faster through a solid, since the molecules are closer together, than through a gas, whose molecules are further apart. This is why it is easier to hear the sound of a paper clip being dropped through a solid (the desk-bound), than it is when the vibrations are traveling through a gas (air). Sound waves will travel more than 10 times faster through a wooden table than they practice through the air!

The pitch of a sound is measured by its frequency, or the number of vibrations produced in 1 second. A guitar string, for case, volition vibrate at a set number of vibrations per second, producing a specific sound. This specific rate of vibration is known as resonant frequency. All objects have a natural resonant frequency at which they vibrate. When plucked, a stretched prophylactic band will vibrate at its resonant frequency. Different rubber bands will produce different resonant frequencies, depending on their thickness or width, and how tightly they are stretched. Thicker, heavier, and loosely stretched safety bands will audio lower pitched, while thinner, lighter, tightly stretched condom bands will sound higher.

Topics for Science Class Discussion

• What other factors practise you recollect might affect how well sound travels through a medium?

• How is sound created in instruments that don't take strings?

• How is a shoebox with rubber bands wrapped around it similar to a guitar?

• How are audio waves dissimilar than light waves?

Extended Activities and Links

• Experiment farther with resonant frequency past collecting several glasses of different shapes or sizes, and gently tapping them with a spoon. The sounds they release are at their individual resonant frequency. Have students organize the spectacles from left to correct in gild of increasing pitch/resonant frequency.

• Sound also tin be produced by using the air spaces that certain objects accept inside. Gather a few different kinds of plastic or glass bottles or jugs, and take students accident air over the top of the opening of each bottle or jug. Draw the kind of sound produced past each ane. Have students try to change the sound produced by filling the bottle/jug half full of water. How does the pitch change? What if the bottle/jug is one tertiary full? A quarter full? Two thirds?

• Assign students to research a musical instrument. Accept them explicate how and why their instrument produces a distinctive sound.

• Explore sound waves through online interactive animations:

• Explore the science of music through online activities

This lesson plan was created by the New York Hall of Science in collaboration with Science Friday equally part of Teachers Talking Scientific discipline, an online resource for teachers, homeschoolers, and parents to produce costless materials based on very pop SciFri Videos to help in the classroom or around the kitchen tabular array.

The New York Hall of Science is a scientific discipline museum located in the New York City borough of Queens. NYSCI is New York City'southward only hands-on scientific discipline and applied science center, with more than 400 easily-on exhibits explore biological science, chemical science, and physics.

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