Chapter+5

=Chapter 5= toc =Section 1= What do you think? There is string across a table with a weight attached to the end to increase tension. The girl is strumming the string and it makes a loud noise. People who play string instruments change the sound they move their fingers to different parts of the string to change the pitch of the note. They would position their hands close together in order to make the highest pitch.

Physics Talk Sound is caused by vibrations. Waves going back and forth are vibrations. Pitch is how high or low a sound is. When plucking a string the pitch changes when you change the distance and also changing the amount of tension on the string. The crest is the point where the amplitude is the greatest. Trough is the point where there is the least amount of amplitude.

Checking Up 1) As the tension increases so does the pitch. 2) As the length of the string becomes shorter, the pitch gets higher. 3) As the mass on the end of a string increases, so does the pitch. 4) Vibration in the object.

Physics To Go 1)a) By adding mass to the end of the string you can increase tension. b) As the tension is increased, the higher the pitch gets. 2)a) You can shorten the length of the string to make the pitch higher. b) With more tension, the string vibrates more, so the sound is higher. 3)a) By increasing the amount of tension. b) You can increase the length of the string. 4) If you increase the tension and increase the length the sound will be lower. 5)a) A musician changes the sounds by moving their finger up and down on the strings to change the pitch. b) The tension of the strings change with the pressure applied. 6)a) The tuners on the side of the guitar change the tension of the strings. b) If an instrument is out of tune it means that the strings are too tight or too loose. c) It would make the pitch lower.

What do you think now? To make the sound higher you put your hands up higher on the instrument. The shorter the strings the higher the sound will be. Musicians make different sounds by moving there hand up and down their instruments making the strings seem longer or shorter to change the pitch.

=Section 2= What do you think? There is a person surfing a wave in the ocean. The water forms a wave by building on top and moving forward towards the shore.

Physics Talk The medium is the material through which a wave can travel. A periodic wave is a repetitive series of pulses; a wave sequence in which the particles od the medium undergo periodic motion. Crest is the highest point of displacement of a wave. Trough is the lowest point of displacement of a wave. Amplitude is the maximum displacement of a particle as a wave passes the height of a wave crest. The higher the energy the higher the amplitude. Frequency is the amount of waves per second. A node is a point on a standing wave where the medium is motionless.

Checking Up 1) A wave is a transfer of energy with no net transfer of mass. 2) A longitude waves energy is parallel with the motion of the wave and a transverse wave is when the energy is perpendicular to the mo,tion of the wave. 3) A node is a point on a standing wave where the medium is motionless. An antinode is a point standing wave where the displacement is the largest.

Physics To Go 1a. Amplitude was calculated by finding the max displacement of the wave - wavelength was found by measuring from the crest to the end of trough - frequency is the reciprocal of the period or the number of waves in the spring - speed is measured by taking the distance divided by the time 1b. amplitude= meters, wavelength=meters, frequency= Hz, speed=m/s 1c. Amplitude is independent, but the rest of the factors are related to eachother. 2a. When shaking the spring quickly, frequency will increase and wave length will decrease because they are inversely related. 2b. Wavelength and frequency both change. 2c. Amplitude and wave speed stay the same. 3. You can measure the wave length by measuring from one point on one wave to the same point on the next wave. 4. You measure the frequency by counting the number of waves completed every second. 5a. The units of wavelength are meters. 5b. Frequency is measured in Hertz 5c. Speed is measured in meters per second. 5d. Wave speed is found by multiplying the frequency by the wavelength. 5e. frequency(s) x wavelength(m)= speed(m/s) 6a. A standing wave is one that remains constant c. By measuring the displacement between two of the same points on this wave, you can find the wavelength. 7a. A longitudinal wave is when the energy is parallel to the medium, and a transverse wave is when the energy is perpendicular to the medium. 7b. The transverse wave is when the spring would move from left to right, but a longitudinal wave is when it moves up and down. 7c. The wave was generated by the law of conservation of energy. It hits the end of the spring and bounces back. 8a. By increasing the frequency, the wavelength is made shorter. 8b. By decreasing the frequency, the wavelength is made longer. 9a. 1 meter, 2 meters, 3 meters, 4 meters, 5 meters 9b. Frequency and wave patters are related because the more wave patterns that are created, the higher the frequency is. 10a. 20 meters 10b. The period is -2, and its reciprocal is -1/2 10c. s=d/t 20/2 s=10m/s 11a. By adding them you know that the amplitude is 5 meters. 11b. If they were in opposite directions, the amplitude would be 1 meter because you would subtract. 12.s=d/t s= 9/2.64 s= 3.41m/s 13a. They are in the node position, where it is not moving. 13b. (.5)*3= 6m is the wavelength 13c. It could also be 3 or 1.5 because it would be split in half.

What do you think now?

=Section 3= What do you think?

Physics Talk Length of the string determines wavelength, it is double the string - shorter string= higher frequency - speed=lengthxfrequency - frequency and wavelength have an inverse relationship meaning that when one decreases the other increases - tension doesn't effect wavelength - larger tension, larger acceleration, strings vibrate faster - wave speed increases, frequency increases and so does pitch - L=n(1/2) lambda - T=time/10 - frequency= number of vibrations/time

Checking Up Questions 1) The wavelength is indirectly proportional to the frequency. lambda= 2L/n 2) As tension increases the pitch increases also, the more tension there is, the larger the acceleration is so that the strings vibrate fasters; this increases the pitch. 3) The higher the tension, the higher the frequency; as the frequency increases, the wave speed increases too. 4) L=n(1/2)lambda

What do you think now?

=Section 4= What do you think?

Physics Talk Sound is a compressional wave. The molecules of air squeeze together or spread out as the sound wave travels through the air. The waves amplitude is zero at the bottom of a test tube, this is the node of a standing wave. At the end of the open test tube the amplitude is as large as possible and it is therefor an anti-node. Sound waves travel by spreading out our bending around barriers. Diffraction is the ability of sound waves to spread out or change direction as they emerge from an opening. The smaller the opening, the more sound waves diffract. a smaller opening produces more diffraction, the size of this opening may be determined by the wavelength of the sound wave if both ends of a tube are open, the air molecules at both ends move abck and forth forming a vibrating column of air in the straw open at both ends, 1/2 lambda, fits in the length of the straw L, the wavelength of the sound is 2L in the straw closed at one end, 1/4 lambda fits in the length of the straw L, therefore the wavelength of this sound is 4L

Checking Up 1) Sounds travels through the medium of air. It uses diffraction to get around obstacles and in and out of large or small openings. 2) Waves diffract by bending and changing direction to fit through different sized openings. 3) The speed of a wave is still the wavelength multiplied by the frequency, if wave speed remains constant, the other two variables remain constant as well.

PTG 1)a) Because they both create a standing wave, they have similar sounds. b) A tube has an anti-node at one end and a string has a node at both ends. 3)a) 11 meters is the longest organ pipe. c) L= n(1/2)lamda L=1(1/2)lamda 19=1/2 lamda d) A large wavelength means a smaller frequency because they are inversely related. 4)a) Since it is 4 times the length of the tube, the wavelength would be 12 meters. b) v=f(lambda) 340= f12 f= 28.3Hz c) Since it is an open tube, it is twice the length of the tube, meaning that it will be 6 meters. d) v= f(lambda) 340= f6 f= 56.5Hz 5) It will be 4 meters long meaning the frequency will be much greater, 85Hz. 6)a) It is called diffraction. 7) v=d/t 340=1600/t t=4.71 s