Ch5+BensonR

= **Wiki Chapter 5** = toc

Section 1
What do you see? I see a boy stretching a string using a can and plucking it to make a sound. It is so loud it blows the other boy back. There is also a dog playing a mandolin type instrument.

What do you think? They make different sounds by tightening and loosening their strings and by finger placement and plucking/stroking the strings with their fingers in order to make the strings resonate and give off a frequency/hertz. They would put their fingers closer to the area where the string is plucked.

**Road Technician Hw** A sound Technician makes sure that any audio coming from an amp or a microphone is picked up and able to be heard by the audience. They also need to make sure that the singer is heard over the audience. They run all the sound checks for the microphones.

**Physics Talk**

**Summary** Vibrations must be present for sound to exist. Variables that affect sound= length and tension Adding mass increases tension on the string which increases the pitch of the sound. When someone tunes an instrument, he/she changes the tension in each string which in turn changes the pitch of the sound created. +tension and -tension= +pitch

**Checking Up Questions** 1. As tension increases so does pitch. 2. Decreasing the length of a string will increase pitch. 3. Adding mass will increase tension of the string which will increase the pitch. 4. In percussion, sound is created by striking an area with a stick which causes vibrations.

**Physics Plus**

ƒ=sqrt(T/4m*L) ƒ=frequency T=tension M=mass of string L=length of string

Explanation ƒ is directly proportional to the sqrt of tension, if you double frequency you need 4 times the tension, sqrt relationship. ƒ is inversely proportional to [1/sqrt(L)], if you double the frequency you need .25 the length, inverse sqrt relationship. As mass increases, frequency decreases, inverse sqrt relationship. It moves smaller in a piano, it is not practical to double the frequency and quadruple the length. If you use a different material you wont need such a long length.

**Inquiring Further** Hearing is the feeling and perception of vibrations in the air. Deaf people don't live in a world of silence, they feel the vibrations, they just can't decipher the vibration/. It is harder to feel higher frequency vibrations, Dame Evelyn Glennie had to use different alternative ways to hear. She felt vibrations through the walls by putting her hands up against the wall while her teacher played notes. This is how she learned and heard things through vibrations.

**Physics To Go** 1a.) You add or take away more mass to the end of the string to increase the tension. 1b.) When there is more tension the pitch is higher. 2a.) You change the length of a string by holding the string in different positions. 2b.) The shorter the string is, the higher the pitch is. 3a.) If you add more tension in the string, the pitch will stay the same if you make the string longer and vice versa. 3b.) The shorter the string is the less tension you need to keep the pitch the same. 4.) If you changed both, the pitch would either be higher lower or the same depending on how you changed each. 5a.) They are able to play different notes after it is tune because they change the tension and the length of the strings which changes the sound. 5b.) To tune a guitar you fix the strings and make them either shorter or longer. You also adjust it by adding tension. To tune a piano by tightening the knobs which increases the tension 6a.) The purpose of the knobs are that they tighten the strings which add tension. 6b.) Guitars need tuners so you can produce a variety of different sounds and pitches with them. 6c.) The tension becomes weaker and the pitch is lower 7a.) The frets on a guitar decide the guitars vibrating length. 7b.)They dont have frets. 7c.) They need more finger accuracy because there are a lot more strings on each so you need to make sure you get the right pitch.

Section 2
**What do you See?** There is a girl surfing on the waves created by a spring, which looks like water waves.

**What do you Think?**

The top of the wave, or the crest is moving faster than the bottom of the wave and thus crashes on the beach before the bottom.

**Physics Talk Summary** A wave is the transfer of energy without a net transfer of mass. To transfer energy through a certain object, you have to use chemical or mechanical energy. The energy is then transferred to the object. The medium is the material that the energy is transferred through. The medium for a water wave for example is the surface of the water. Waves continue to travel unchanged by the wave ahead of them. A periodic wave is a repetitive series of pulses. It keeps repeating after a certain amount of time. The crest is the highest point on a wave and the trough is the lowest point. The amplitude is the highest displacement of the wave. It is equal to the height of the crest. The wavelength is the distance from one point on the wave to the same point on another wave. The frequency is the number of vibrations over a given amount of time. The period is the amount of time it takes the wave to complete one full cycle. Period= 1/frequency. Frequency= 1/Period. They are inversely related. A transverse wave is when the direction of the medium is perpendicular to the direction of the wave. In a compressional wave they are parallel. A standing wave is a wave pattern that moves in a constant position. The node is the spot on the wave where the standing wave is motionless. It is the position where there is always destructive interference. An antinode is where the displacement is the biggest on a standing wave. It is the position on a standing wave where htere is constructive interference. On a wave it is the part that is open, the node is the pinched in part. The speed of a wave is distance over time. The number of waves is that number harmonic. The length of a string= n(1/2) lambda. The higher the harmonic, the higher the pitch. Interference is a wave property. It is when two separate waves are in the same place at the same time. When the waves amplitude of a crest and a tough are in two different directions and amplitudes subtractl, that is destructive interference. Constructive interference is when crest meets crest or trough meets trough and the amplitudes add.

**Checking Up Questions** 1.) A wave is the transfer of energy through an object without the net transfer of mass. 2.) A transverse wave is when the direction of the medium is perpendicular to the direction of the wave, and a compressional wave is where the medium is parallel to the direction of the wave. 3.) A node is the motionless spot on a standing wave and an antinode is where there is the biggest displacement on a standing wave.

**Physics To Go** 1a.) amplitude- We measured 10 centimeters out, 20 centimeters out, and 30 centimeters out. That ended up being our amplitude. wavelength- The crest to the end of the trough.  frequency-The reciprical of the period or the number of waves in the spring  speed- We took the distance that the spring went and divided it by the time it took to reach that distance. or wave length times frequency  1b.) amplitude- meters wavelength- meters frequency- Hz speed- m/s 1c.) Everything is related to each other except for amplitude which was independent. 2a.) As you shake the coiled spring more rapidly, the frequency changes, it becomes higher, so the wave length is shorter. The medium changes the speed. 2b.) The speed changes. The speed is higher. 2c.) The amplitude of the wave stays the same. 3.) You can measure the wave length by measuring from one point on the wave to the same point on another wave. 4.) The frequency is the number of vibrations over time. You would be able to measure the frequency by seeing how many waves are made compared to the amount of time you were recording. 5a.) The units of wavelength are meters 5b.) The units of frequency are Hertz. It is the number of waves per time 1/time 5c.) Speed is m/s 5d.) You can measure the speed with these by the wavelength times the frequency. 5e.) meters (wavelength) x 1/seconds= meters/ seconds 6a.) A standing wave is a wave that remains in constant position as it follows a pattern. 6b.)

6c.) You can find the wave length by measuring from one position on the wave to the same position on another wave because the pattern is constant. 7a.) longitudinal waves are ones where the energy is parallel to the medium and a transverse wave is one where the energy is perpendicular to the medium. 7b.) Coiled springs can be either. They can be a transverse wave if the person is moving it from side to side, left and right. They can be longitudinal if the person pushes to spring forward and backwards. 8a.) To make the wavelength shorter i would increase the frequency by shaking the spring more rapidly. 8b.) I would do the opposite to make it longer. I would decrease the frequency by shaking the spring slower. 9a.) 1 meter, 2 meters, 3 meters, 4 meters, 5 meters 9b.) The frequency and the wave patterns are related to each other because the more wave patters that are made, the higher the frequency 10a.) 20 meters 10b.) The period is 2- frequency is reciprocal. The frequency is 1/2 Hz 10c.) speed= distance/ time speed= 20/2 speed= 10 m/s 11.) 3 meters+ 2 meters 5 meters- amplitude  11b.) If they were in opposite directions you would subtract them and the amplitude would be one meter. 12.) Speed= meters/ seconds speed= 4.5(2)/2.64  Speed= 9/2.64  3.41 m/s  13a.) The node is the position they are in  13b.) It is 6 meters- 3 meters+3 meters  13c.) It could also be 3 or 1.5 because it could be split in half.

Physics Plus **Essential Question** All waves' particles just go up and down. The energy is the actual wave so the source of the wave is the initial shake so the water or whatever material goes apart from the middle.

**What do you Think Now?** Wind is the medium that allows water to move, it travels perpendicular to the medium which makes water transverse. The water moves up and down as it approaches the beach, creating amplitude.

Class Work A) 4m B) 5s C) 0.2 Hertz D) 8 m  E) 1.6 m/s

Section 3
**What do you See?** There are 2 people playing instruments, one playing the harp which contains many strings and the other is just playing one string.

**What do Think?** As the length of the string decreases, pitch increases. This is an inverse relationship.

**Physics Talk** The length determines wavelength. Higher frequency= shorter length. Speed=l*f Tension does not affect length. Frequency affects wave speed. Larger the tension the faster the strings vibrate. When speed increases so does frequency and pitch. L=n*Wavelength/2 T=Time/10 F=vibrations/time **Checking up Questions** 1.) The equation is lamda= 2L/n. Frequency is higher when wavelength is smaller.

2.) As the tension increases, the pitch increases, this is because the more tension the faster the string vibrates which causes an increase in pitch. 3.) The higher tension= higher frequency. As the frequency increases, the wave speed increases. 4.) L= n*wavelength/2

**What do Think Now?** When tension is greater, it is more difficult for the string to produce a wave affecting pitch, as frequency increases pitch decreases.

Section 4
**What do you see?** There are multiple people playing wind instruments, the shorter ones seem to be more difficult to play as the players are blowing harder. Different notes are coming out of each instrument. **What do you Think Now?** When certain holes are covered, you can blow into the instrument and depending on the holes covered travel shorter or further. Depending on finger position this lengthen or shortens the instrument and pitch. **Physics Talk Summary** Sound=compressional wave. It compresses together then pushes out like a spring. Air is the medium sound uses to travel through. No vibration+no amplitude=no sound. In an open tube, the open end is where the sound is loudest and amplitude at its maximum. Sound travels by moving around objects. Diffraction=bending of waves smaller the opening, the more diffraction. Size of opening determine wavelength and volume. When one end is closed, pitch and frequency decrease.

**Checking up Questions** 1.) Medium of sound is air, using diffraction sound travels through the air. It is able to travel through openings as it is in wave form. 2.) Waves diffract by bending and changing directions upon finding openings in order to get through. 3.) The speed=wavelength*f. If speed is constant, so is frequency and wavelength.

**Physics to Go** 1a.) Both produce waves 1b.) Plucking a string is compressional and blowing into a pipe is transverse. 3a.) 11 meters 3b.)



3c.) L= n(1/2)wavelength L=1(1/2)wavelength

19=1/2wavelength

22 m, two times the length. 3d.)The larger the wavelength, the lower the frequency....there is one antinode. 4a.) 12 meters 4b.) v=(frequency) (wavelength) 340= (12)(frequency)  frequency= 28.3 Hz  4c.) 6. It is double the length because it is an open tube. 4d.) v=(frequency) (wavelength) 340= (frequency)(6)  frequency= 56.7 Hz  5.) 4 meters long and a higher frequency, 85 Hz.  6a.) Diffraction  6b.)



7.) v=d/t 340= 1600/t  t=4.71 s  **What Do You Think Now?**  Flutes and organs produce sounds by pushing air through their open tubes. One end of each tube is open while the other contains a mouth piece that pushes air through the tube. Antinodes are formed at the ends because the tube is open. This causes the sound to be loudest because sound is loudest when the amplitude is at it's maximum, which is at the antinode. The larger the tube, the lower the frequency and pitch. As wave speed increases, so does frequency. Wave speed should always be constant, depending on temperature, at 340 m/s.