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01 Periodic Motion Unit Test 1
1、 A mass of 0.20 kg , hung from a spring with a spring constant of 80.0 N/m , is set into an up-and-down simple harmonic motion. If the mass is displaced from equilibrium by 0.10 m and released from rest, what is its speed when moving through the equilibrium point?
答案: 2.0 m/s
2、 The Fig. is the v ( t ) curve for an object undergoing SHM. Which of the following is the oscillating function x ( t ) for the object?
答案: 
3、 A mass m attached to a vertical spring (with spring constant k ) is released from rest from the relaxed position of the spring. What is the amplitude of the resulting oscillation?
答案: 
4、 A mass hanging on a spring oscillates vertically. If the equilibrium point of the oscillation is a distance d below the relaxed length of the spring and if the amplitude of the oscillation is A . Which is the maximum kinetic energy of the oscillation?
答案: 
5、 A simple pendulum consists of a massive bob connected to the end of a very light string. Ignore air resistance. Which one of the following changes should be made in order to increase the period of the pendulum?
答案: Increase the length of the string.
6、 A block is attached to a spring hung vertically. After being slowly lowered, it is hung at rest with the spring stretched by 15.0 cm. If the block is raised back up and released from rest with the spring unstretched, what is the amplitude of its oscillations?
答案: 15.0 cm
7、 A damped harmonic oscillator with the natural angular frequency 
and very little damping is driven by an external force 
. When it reaches the stable state, the oscillating angular frequency is______
答案: 
8、 The graph of vibration of the particle in SHM is shown in the figure. The period of the vibration equals___ s.
答案: (以下答案任选其一都对)4.8;
4.8 s;
4.8s
9、 A 1.0 kg block is attached to a spring with spring constant 16 N/m and is at rest on a smooth horizontal plane. It is hit with a hammer and acquires instantaneously a speed of 0.40 m/s. The speed of the block at x = A/2 is _____ m/s (round to two decimal places ).
答案: 0.35
10、 An object of mass m is attached to a horizontal spring, stretched to a displacement A from equilibrium and released, undergoing harmonic oscillations on a frictionless surface with period 
. The experiment is then repeated with a mass of 4m. The ratio 
of the new period of oscillation and the old period is_____ .
答案: (以下答案任选其一都对)2;
2.0
作业01 Periodic Motion Week 1 Chapter 13 Periodic Motion
1、 Week 1- The homework of Chpater 13
评分规则: Please upload your homework photos here.
02 Mechanical Waves Unit Test 2
1、 
答案: 
2、 
答案: 
3、 
答案: 
4、 While a guitar string is vibrating, you gently touch the midpoint of the string to ensure that the sting does not vibrate at that point. Which normal modes cannot be present on the string while you are touching it in this way?
答案: n = 1, 3, 5,…
5、 
答案: 75.0m
6、 The six strings of a guitar are the same length and under nearly the same tension, but they have different thicknesses. On which string do waves travel the fastest?
答案: The thinnest string.
7、 
答案: 9
8、 
答案: 
9、 A traveling wave is propagating in an elastic medium and at time t the particle at position P has the maximum displacement. The potential energy of the particle at position P is _____ (filling in “maximum”, “minimum”, or “zero”).
答案: (以下答案任选其一都对)ZERO;
zero
10、 A stretched string fixed at two ends has a mass of 0.08kg and a length of 8.00m. The tension in the string is 64.0N . There exists a standing wave on the string. For the third harmonic, the vibration frequency is Hz (Keep only the integer portion).
答案: 15
作业02 Mechanical Waves Week 2 Chapter 15 Mechanical Waves
1、 Week 2- The homework 1 of Chpater 15
评分规则: Please upload your homework photos here.
03 Sound and Hearing Unit Test 3
1、 You use an electronic signal generator to produce a sinusoidal sound wave in air. You then increase the frequency of the wave from 100Hz to 400Hz while keeping the pressure amplitude constant. What effect does this have on the displacement amplitude of the sound wave?
答案: It becomes 1/4 as great.
2、 A tuning fork placed over a 0.57m column of air closed only at its bottom end produces a standing wave in the 3rd harmonic. The speed of sound in air is 342m/s. What is the frequency of the tuning fork?
答案: 450Hz
3、 A standing wave is created in an air-filled tube open at both ends when a tuning fork of frequency 552Hz is placed near one of the open ends. A tuning fork of frequency 644Hz produces the next higher harmonic for this tube. Assume that the speed of sound in air is 340m/s. What is the length of the open tube?
答案: 1.85m
4、 A flute has a length of 58.0 cm. If the speed of sound in air is 343m/s , what is the fundamental frequency of the flute, assuming it is a tube closed at one end and open at the other?
答案: 148 Hz
5、 
答案: 
6、 A stopped organ pipe of length L has a fundamental frequency of 220 Hz. For which of the following organ pipes will there be a resonance if a tuning fork of frequency 660Hz is sounded next to the pipe?
答案: A stopped organ pipe of length L.
7、 If a 1000Hz sound source moves at a speed of 50.0 m/s toward a listener who moves at a speed of 30.0 m/s in a direction away from the source, what is the frequency heard by the listener? (The speed of sound is 340 m/s.)
答案: 1069 Hz
8、 When two tuning forks are sounded at the same time, a beat frequency of 5Hz occurs. If one of the tuning forks has a frequency of 245Hz , the frequency of the other tuning fork is Hz.
答案: (以下答案任选其一都对)250;
240
9、 Suppose that speaker A emits a sinusoidal sound of frequency 500Hz and speaker B emits a sinusoidal sound wave of frequency 1000Hz . If will the interference happen between these two waves meeting? __ (fill in yes or no)
答案: (以下答案任选其一都对)No;
no;
NO
10、 You were at rest and a police car with its siren on was passing you with a constant speed. You found that the frequencies of the siren were respectively 550Hz and 450Hz when the police car was moving toward and away from you. Assume that the speed of sound in air is 340m/s. The speed of the police car was m/s .(Keep only the integer portion)
答案: 34
作业02 Mechanical Waves Week 3 Chapter 15 Mechanical Waves
1、 Week 3 homework.
评分规则: Please upload homework’s picture.
作业03 Sound and Hearing Week 4 Chapter 16 Sound and Hearing
1、 Week 4 homework
评分规则: Please upload homework’s picture.
04 The Nature and Propagation of Light Unit Test 4
1、 Some crystals are not isotropic: light travels through the crystal at a higher speed in some directions than in others. In a crystal in which light travels at the same speed in the x-and z-directions but at a faster speed in the y-direction, what would be the shape of the wave fronts produced by a light source at the origin?
答案: ellipsoidal, stretched out along the y-axis.
2、 The index of refraction for water is about n=4/3. What happens to light when it travels from air into water?
答案: Its speed decreases to 3c/4 and its wavelength decreases by a factor of 3/4.
3、 A ray of light in diamond (index of refraction 2.42) is incident on an interface with air. Where is the largest angle the ray can make with the normal and not be totally reflected back into the diamond?
答案: 24.40
4、 A polarizer and an analyzer are oriented so that the maximum amount of light is transmitted. The natural light of intensity I is incident on the polarizer. When the analyzer is rotated through 45.00, which is the intensity of the light through the analyzer.
答案: 0.25I
5、 Unpolarized light of intensity I is incident upon three polarizers. The transmission axis of the first polarizer is along the z -axis, that of the second polarizer is 30° rotated through from the z-axis, and that of the third polarizer is rotated in the same direction through 75° from the z-axis. What is the light intensity after the light beam passes through the third polarizer?
答案: 3I /16
6、 A parallel beam of unpolarized light in air is incident at an angle of 54.5° (with respect to the normal) on a plane glass surface. The reflected light is completely linearly polarized. What is the angle of refraction of the transmitted light?
答案: 35.50
7、 A beam of unpolarized natural light is incident on a reflecting surface between two transparent materials. If the reflected light is completely linearly polarized, then the refracted light is
答案: partially polarized with the polarization parallel to the plane of incidence greater than that perpendicular to the plane of incidence.
8、 What happens to light when it is reflected off a shiny surface on a sunny day?
答案: It tends to be partially polarized.
9、 You are taking a photograph of a sunlight high-rise office building. In order to minimize the reflections from the building’s window, you place a polarizing filter on the camera lens. How should you orient the filter?
答案: with the polarizing axis horizontal.
10、 A spherical wave is traveling in air. According the Huygens’s Principle, what shape is its wave front at some later time?
答案: Spherical surface.
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