Ch5+Let+us+Entertain+You

Section 1toc
What do you see? - There are two boys playing with a string. They are plicking the string and it is causing a lot of noise.

What do you think? - They tighten and loosen the strings on the instrument. This causes the noise to be louder or softer. - If someone where to pretend to play the guitar they would position one hand far out away from there body and the other at there belt bucket. With the hand at the belt bucket they would strum the air strings to make it look like they are playing a guitar.

Physics Talk - Sound is caused from vibrations. Variables are the things that change in an experiment. Length and tension on strings are the variables that cause a change in the pitch of an instrument. - Pitch is how high or low the sound is, it has nothing to do with volume. Guitarists for example change their pitch by holding the strings tighter and closer to the front of the guitar if they want to make the pitch higher. - As the tension increases, the pitch is higher and as the string is shorter, the pitch is higher. Vibrations cause sound from a percussion instrument.

Checking up Questions 1. As the tension increases, the pitch gets higher. 2. When the string is shorter the pitch gets higher. 3. The pitch was higher because the mass causes the tension to increase. 4. Vibrations are what causes sound from a percussion instrument.

Physics Plus Physics To Go 1. a. You add or take away more mass to the end of the string to increase the tension. b. When there is more tension the pitch is higher. 2. a. You change the length of a string by holding the string in different positions. b. The shorter the string is, the higher the pitch is. 3. a. If you add more tension in the string, the pitch will stay the same if you make the string longer and vice versa. b. 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. 5. a. 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. b. 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 6. a. The purpose of the knobs are that they tighten the strings which add tension. b. Guitars need tuners so you can produce a variety of different sounds and pitches with them. c. The tension becomes weaker and the pitch is lower 7. a. The frets on a guitar decide the guitars vibrating length. b. They dont have frets. c. 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.

What do you think Now? - They tend to make the strings tighter or looser which causes the sound to be higher or lower. - They would pretend to strum the air like they were strumming a guitar. They would tune it to make the sound sound different.

Section 2
What do you see? - Looks like the girl is surfing on a wave, but she is surfing on a spring. There is some similarities between the waves on a spring and the waves in the ocean.

What do you think? - The water builds up and this build up causes the wave to bend. This bend is the wave. This wave moves very fast because of all the pressure at the center of the wave.

Checking Up Questions 1. Wave - is the transfer of energy through an object without the net transfer of mass. 2. 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. 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 1 a. 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 b. amplitude - meters wavelength - meters frequency - Hz speed - m/s c. Everything is related to each other except for amplitude which was independent. 2 a. 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. b. The speed changes. The speed is higher. c. 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. 5 a. The units of wavelength are meters b. The units of frequency are Hertz. It is the number of waves per time 1/time c. Speed is m/s d. You can measure the speed with these by the wavelength times the frequency. e. meters (wavelength) x 1/seconds= meters/ seconds 6 a. A standing wave is a wave that remains in constant position as it follows a pattern. b.  c. 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. 7 a. 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. b. A transverse wave is a wave in which the direction the medium moves is perpendicular to the direction of the wave. A compressional wave is a wave in which the direction the medium moves is parallel to the direction the waves move. 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. b. 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 b. The frequency and the wave patterns are related to each other because the more wave patters that are made, the higher the frequency 10a. 10 meters b. The frequency is 1 Hz c. speed= distance/ time speed= 20/2 speed= 10 m/s 11. 3 meters+ 2 meters 5 meters- amplitude b. 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 13. a. node b. 6 meters c. There were 4 others. They are not visible because they are so small.

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.

Classnotes node: position on a standing wave where there is always destructive interference antinode: position on a standing wave where there is constructive interference of antinodes = harmonic # x/2(wavelengths) = L amplitude- you can measure the distance between the equilibrium and the crest frequency- see how many times the wavelength happen in the spring

What do you think Now? - The water moves by creating pressure that builds up. This pressure causes there to be a wavelength and this wavelength creates the wave. The different amount of pressure causes the wave to be big or small.

5/13/11 a) amplitude- 4 m b) period- 5 s c) frequency- 1/5 hz d) wavelength- 8 m e) wave speed- (.2)(8) = 1.6 m/s

Section 3


What do you think Now? - The tighter the string the higher the pitch. It is because the string controls the sound and the tension causes the pitch. The pitch changes because of the tighter or looser string.

Section 4
What do you see? - There are kids playing music out of different types of household items. They are different types of wind instruments.

What do you think? - They produce sound because the human is blowing air into them which is causing the air to go through different holes in the flute and or organ and make sound.

Physics Talk Summary - Sound is a compressional wave. It compresses together then pushes out like a spring. The medium that sound travels through is air. At the bottom of a test tube there is no vibration and the amplitude is zero so there is no sound. It is at the **node** of a wave. At the open end, it is the loudest it can go and the **amplitude** is at its maximum. This is the **antinode** of a wave. Sound waves travel by moving around barriers. DIffraction is this ability for the waves to be able to bend, spread out and change direction in order to get into an opening. The smaller the opening the more diffraction. The size of the opening determines the wavelength and volume. If both ends of a tube are open, it forms a vibrating column of air. The displacement of the air molecules are zero. When one end is closed, the pitch and frequency decrease. If the both ends are open it is 1/2 lambda. The Wavelength is double then if it were closed.

Checking up Questions 1. The medium is air. Sound travels through the air using diffraction. 2. Waves diffract by finding openings and bending and changing directions in order to get through them. 3. The speed of a wave is the wavelength times the frequency. If the wave speed is constant than the frequency and wavelength are constant.

Physics to Go 1a. They both produce waves b. Plucking a string is compressional and blowing into a pipe is transverse. 3a. It is 11 meters b. c. L= n(1/2)lamda L=1(1/2)lamda 19=1/2 lamda It is two times the length. 22 m. d. The larger the wavelength the lower the frequency because there is only one antinode 4a. It is 12 meters long. b. v=frequency (wavelength) 340= 12(frequency) frequency= 28.3 Hz c. It is 6. It is double because it is open. d. v=frequency (wavelength) 340= frequency(6) frequency= 56.7 Hz 5. It will be 4 meters long and the frequency is a lot greater. It is 85 Hz. 6a. It is called diffraction b.

What do you think? -