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4. [0.4/1 Points] PREVIOUS ANSWERS WAUNIPHYSAV1 15.P.020. ASK YOUR TEACHER PRACTICE ANOTHER In the diagram below, the blue curve refers to a slnusoidal wave on a string at tlme t1 = 0 that is propagating to the right The red curve represents the same wave at a later time (2 = 0'75 5, before the wave has traveled one full wavelength. y (all) x (ml) (a) Which of the following wave functions correctly represents the above situation? Here A represents the amplitude, k the wave number, and a) the angular frequency of the wave. @ y(x, t) = A sin(kx mt) O y(x, t) = A sin(kx + wt) 0 y(x, t) = A cos(kx wt) 0 y(x, I) = A cos(kx + wt) q! (b) What is the speed of the wave? 13.3 x How far has the wave traveled in the time interval ('2 t1? How can you determine the speed from this information? cm/s (c) What are the amplitude, wave number, and angular frequency of the wave? A=-x What the maximum value of y? cm m=x How is the angular frequency related to the wave number and wave speed? rad/s PREVIOUS ANSWERS WAUNIPHYSAV1 15.P.049. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER At t = O, the instantaneous position of two pulses moving along a taut string with a speed v = 22.8 cm/s are as shown In the diagram below. Each unit on the horizontal axis ls 5.0 cm and each unit on the vertical axis is 5.0 cm. (The peak of pulse 2 is exactly on a half unit of the horizontal axis.) 1. [0.34/1 Points] (a) At what location will the resultant of the two pulses have maximum amplitude? -x The amplitude of the resultant will be maximum when the peaks of the two pulses overlap. How far does each pulse move to get to this position? cm (b) At what time will the resultant of the two pulses have maximum amplitude? x what is the relationship between speed, time, and distance? 5 n (c) What is the value of this maximum amplitude? Ev cm 4. [0/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.011. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Two speakers, each with a power output of 0.370 W, are mounted facing each other and 33.8 m apart. If the speakers are each broadcasting an amplified static buzz uniformly in all directions, determine the following. (a) the total sound intensity a person hears when they are midway between the speakers 0.0001167 How are intensity, power, and area related? What is the area of interest in this problem? How does the sound intensity from the two speakers compare? W/m2 (b) the total sound intensity the person hears after they move directly toward one of the speakers for a distance of 5.7 m 0.0001167 X How are intensity, power, and area related? What is the area of interest in this problem? w/m21. [0.5/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.041.TUTORIAL. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Two speakers, s1 and s2, are located 0.550 m apart as shown in the figure below. Sally stands 0.750 m away from speaker s1, indicated by the "X" on the figure. The speakers are connected to an adjustable oscillator and always emit the same sound in phase at the same frequency. (Use 343 m/s for the speed of sound in your calculations.) S , S , X a) If Sally cannot hear anything at her location due to destructive interference of sound from the two speakers, what is the lowest possible frequency of sound the speakers emit? 952 Hz (b) The frequency is now changed to 1901 Hz. Sally stands at the same point. Her friend Mark moves speaker s2 (along the same axis) to the closest point to speaker s1, but not coinciding with $1, such that Sally hears a maximum of sound intensity. What is the new distance between s, and s2? 0.750 X For constructive interference, how is the path difference related to the wavelength? How is wavelength related to frequency? There are many possibilities that satisfy the constructive interference condition, but which should you choose for smallest nonzero path difference? m 129 Tutorial 2. [0/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.043. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER What beat frequencies result if a piano hammer hits three strings that emit frequencies of 987.8, 164.8, and 196.0 Hz? (Enter your answers from smallest to largest.) 24 smallest X How is the beat frequency for two different sounds related to the frequency of the two sounds? Hz 24 Hz largest 55.4 X How is the beat frequency for two different sounds related to the frequency of the two sounds? Hz5. [0/1 Points] PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.046.TUTORIAL. ASK YOUR TEACHER PRACTICE ANOTHER A diagnostic ultmsound echo is reected from moving blood and returns with a frequency 322 Hz higher than its original 2.00 MHz. What is the velocity of the blood? (Enter the magnitude of the velocity. Use 1540 m/s as the speed of sound through human tissue) 1540 x How is the frequency of sound received by a moving observer related to the frequency transmitted by a stationary source? How is the frequency of sound received by a stationary observer related to the frequency transmitted by a moving source? Think carefully about who or what is the source and observer and the associated speed for each case. Review the sign convention used when writing an expression for the Doppler shift. m/s i3 Tutorial 3. [0/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.008. MY NOTES ASK YOUR TEACHER Dolphins make sounds in air and water. What is the ratio of the wavelength of the sound in air to its wavelength in water? Assume air temperature is 20.0 C and the speed of sound in sea water at 20.0C is 1540 m/s. air = 0.2272 X sea water How are the frequency, wavelength and speed of a wave related? Does the frequency of the sound emitted by the dolphins depend on the medium through which the sound is traveling? 4. [1/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 15.P.044. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER After your school's team wins the regional championship, students go to the dorm roof and start setting off fireworks rockets. The rockets explode high in the air and the sound travels out uniformly in all directions. If the sound intensity is 2.02 x 10-6 W/m2 at a distance of 173 m from the explosion, at what distance from the explosion is the sound intensity half this value? 244 .65 m 5. [0.5/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 16.P.030. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A simplified version of our voice production system consists of considering the breathing passage and the mouth to be a tube closed at one end. (a) Determine the frequency of the fundamental (to the nearest Hertz) if the simulation tube is 0.227 m long and the air temperature is 35.0 C. The speed of sound in air at OC is 331 m/s. 251.6 X For a tube closed at one end, how is the length of the tube related to the resonant wavelengths? How are the speed, frequency, and wavelength of sound related? How is the speed of sound in air at a specific temperature related to the speed of sound in air at 0 C? Hz (b) Assuming that the temperature dependence for helium is the same as for air, determine the frequency of the fundamental (to the nearest Hertz) if the air is replaced by helium. The speed of sound in helium at OC is 965 m/s. 1128.85 Hz4. [0.34/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 32.P.010. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER The magnetic field in a plane electromagnetic wave is represented by the equation B = Bmax sin(ky - wt)i where Bmax = 5.98 x 10- T and k = 4.29 x 107 /m. (Assume a standard xyz right-handed coordinate system.) (a) What is the magnitude and direction of the electric field at the instant the magnetic field is a maximum? (Express your answer in vector form.) Emax = 179.4k X For a plane electromagnetic wave, how are the amplitudes of the electric and magnetic fields related? What is the direction of propagation of the wave in this case? Review the right-hand rule for vector product of the electric and magnetic field vectors. V/m (b) What is the wavelength of the wave? 1.46e-7 X How is the wavelength of EM waves related to the wave number? nm (c) What is the frequency of the wave? 2.05e15 Hz6. [0.67/1 Points] PREVIOUS ANSWERS WAUNIPHYSAV1 32.P.D19. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER (a) What Is the wavelength of 122-MHz radio waves used In an MRI unlt? (Give your answer to at least two decimal places.) m (b) If the frequencies are swept over a i1i20% range centered on 122 MHz, what is the range of wavelengths broadcast? (Give your answers to at least two decimal places.) minimum -X Is the minimum less than or more than the average wavelength? m maximum m 3. [0.67/1 Points] DETAILS PREVIOUS ANSWERS WAUNIPHYSAV1 32.P.031. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER You and your friend Hodges are conducting an experiment with light. Hodges points a light source at you and you measure the peak magnetic field value as B = 5.9 HT. (a) What is the maximum magnitude of the electric field? 1770 v/m (b) What is the maximum instantaneous power per unit area of the light at your location? 83200 X What is the relationship between power per unit area, the Poynting vector, and the electric field? Note that we want the peak value, not the average W/m2 (c) What is the intensity (that is, time-averaged power per unit area) of the light at your location? 4.16e+3 w/m2